diff --git a/.cursor-plugin/plugin.json b/.cursor-plugin/plugin.json index c764713..018e35d 100644 --- a/.cursor-plugin/plugin.json +++ b/.cursor-plugin/plugin.json @@ -148,6 +148,8 @@ "showcase/terrain-scatter", "showcase/fence-kit", "showcase/watchtower", - "showcase/cart" + "showcase/cart", + "showcase/park-bench", + "showcase/wheelbarrow" ] } diff --git a/AGENTS.md b/AGENTS.md index 17d2def..372affb 100644 --- a/AGENTS.md +++ b/AGENTS.md @@ -21,7 +21,7 @@ classifies it as a `cursor-plugin`. This is content the AI loads when the user asks Blender questions or works on Blender add-ons in Cursor or Claude Code. The content base is 16 skills, 9 rules, 3 templates, 27 snippets, 59 -examples, and 11 showcase pieces (counts are CI-enforced against README.md +examples, and 13 showcase pieces (counts are CI-enforced against README.md) and the manifest). The full inventory tables and per-item purposes live in `CLAUDE.md`. Example anatomy and authoring rules: copy `examples/bmesh-gear/`; showcase conventions: `showcase/README.md`. The render look is specified diff --git a/CLAUDE.md b/CLAUDE.md index 45a70d1..22b3227 100644 --- a/CLAUDE.md +++ b/CLAUDE.md @@ -22,7 +22,7 @@ rules/.mdc - Anti-pattern rules, 9 total templates// - Starter projects, 3 total snippets/.py - Standalone code patterns, 27 total examples// - Runnable smoke-gated examples, 59 total (+ gallery.json) -showcase// - Budget-conformance props, 11 pieces (sibling of examples/; see showcase/README.md) +showcase// - Budget-conformance props, 13 pieces (sibling of examples/; see showcase/README.md) scripts/build_gallery.py - Regenerates docs/gallery/ from examples/gallery.json + showcase/gallery.json scripts/site/ - Vendored landing-page build (Jinja2) docs/gallery/ - Committed generated gallery pages + hero renders diff --git a/README.md b/README.md index 2bb0a70..6913e3b 100644 --- a/README.md +++ b/README.md @@ -18,7 +18,7 @@

- 16 skills  •  9 rules  •  3 templates  •  27 snippets  •  59 examples  •  11 showcase pieces + 16 skills  •  9 rules  •  3 templates  •  27 snippets  •  59 examples  •  13 showcase pieces

@@ -37,7 +37,7 @@ ## Overview -This repository ships **16 skills, 9 rules, 3 templates, 27 snippets, 59 examples, and 11 showcase pieces** for Blender Python development targeting Blender 5.2 LTS (current stable) with Blender 4.5 LTS fallback support. Blender 5.1 is prior stable. +This repository ships **16 skills, 9 rules, 3 templates, 27 snippets, 59 examples, and 13 showcase pieces** for Blender Python development targeting Blender 5.2 LTS (current stable) with Blender 4.5 LTS fallback support. Blender 5.1 is prior stable. The content is consumed by AI coding agents (Cursor, Claude Code, any MCP-capable client) when working on Blender add-ons, geometry nodes scripts, batch pipelines, or animation tooling. There is no build step. Edit the markdown and Python files directly. @@ -86,6 +86,8 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show Fence kit: a timber post-and-rail section with pyramidal caps, iron shoes and straps on a dark studio floor Watchtower: a timber lookout with X-braces, hatch ladder, plank platform, and a coursed shake roof on a dark studio floor Cart: a two-wheel wooden cart with spoked wheels, slatted bed, and shafts on a dark studio floor +Park bench: a wrought-iron bench with scrolled legs and wooden slats on a dark studio floor +Wheelbarrow: a staved wooden tray with iron straps, a spoked wheel, rear legs, and handles on a dark studio floor [`shipping-crate`](showcase/shipping-crate/) — procedural crate through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets. Falsifier `--skip-decimate` exits 9. @@ -109,6 +111,10 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show [`cart`](showcase/cart/) — procedural two-wheel wooden cart with spoked wheels, slatted bed, and shafts through the same pipeline. Falsifier `--skip-decimate` exits 9. +[`park-bench`](showcase/park-bench/) — procedural wrought-iron park bench with scrolled legs and slatted seat through the same pipeline. Falsifier `--skip-decimate` exits 9. + +[`wheelbarrow`](showcase/wheelbarrow/) — procedural staved wheelbarrow with a spoked wheel, iron straps, legs, and handles through the same pipeline. Falsifier `--skip-decimate` exits 9. + ## Examples Runnable, smoke-gated demos live in [`examples/`](examples/) — each is executed headless on diff --git a/ROADMAP.md b/ROADMAP.md index 05440a8..f1fab5f 100644 --- a/ROADMAP.md +++ b/ROADMAP.md @@ -115,8 +115,10 @@ Not committed; target list for the next content version. (v0.3.0 shipped the smo - ~~Hero prop with a more complex silhouette (lantern or treasure chest) as a second showcase piece~~ **SHIPPED** as `showcase/street-lantern/` and `showcase/treasure-chest/` — hanging iron lantern with muntined amber cage; slatted chest with iron bands and an open lid; `--skip-decimate` exits 9 on the LOD1 ratio band - ~~Timber watchtower showcase~~ **SHIPPED** as `showcase/watchtower/` — corner posts through a plank platform, lower-bay X-braces, hatch ladder, coursed shake roof; `--skip-decimate` exits 9 on the LOD1 ratio band - ~~Two-wheel wooden cart showcase~~ **SHIPPED** as `showcase/cart/` — slatted bed, shafts, spoked wheels, iron hubs and axle; `--skip-decimate` exits 9 on the LOD1 ratio band -- Wrought-iron park bench (slatted seat, scrolled legs) as a game-prop showcase piece -- Wooden wheelbarrow (staved tray, single wheel, handles) as a game-prop showcase piece +- ~~Wrought-iron park bench (slatted seat, scrolled legs) as a game-prop showcase piece~~ **SHIPPED** as `showcase/park-bench/` — scrolled iron legs, slatted seat and back; `--skip-decimate` exits 9 on the LOD1 ratio band +- ~~Wooden wheelbarrow (staved tray, single wheel, handles) as a game-prop showcase piece~~ **SHIPPED** as `showcase/wheelbarrow/` — staved U-tray, iron straps, spoked wheel, rear legs; `--skip-decimate` exits 9 on the LOD1 ratio band +- Blacksmith anvil on a timber stump as a game-prop showcase piece +- Staved wooden water trough on a stand as a game-prop showcase piece - ~~Small modular kit showcase on recognizable geometry (`modular-kit-snap` contract)~~ **SHIPPED** as `showcase/fence-kit/` — tiling post-and-rail section (AABB X is the tile width; does not re-witness the snap contract); `--skip-decimate` exits 9 on the LOD1 ratio band - ~~Custom ID-property delete witness~~ **SHIPPED** as `examples/cross-version-property-delete/` — IDs built via `bpy.data.objects.new` (not `active_object`); `property_unset` is TypeError and leaves the key; `del` removes it on 4.5 LTS and 5.x diff --git a/docs/gallery/assets/park-bench-hero.webp b/docs/gallery/assets/park-bench-hero.webp new file mode 100644 index 0000000..9d4d4eb Binary files /dev/null and b/docs/gallery/assets/park-bench-hero.webp differ diff --git a/docs/gallery/assets/wheelbarrow-hero.webp b/docs/gallery/assets/wheelbarrow-hero.webp new file mode 100644 index 0000000..0cc4800 Binary files /dev/null and b/docs/gallery/assets/wheelbarrow-hero.webp differ diff --git a/docs/gallery/index.html b/docs/gallery/index.html index ea429dd..00be18e 100644 --- a/docs/gallery/index.html +++ b/docs/gallery/index.html @@ -272,7 +272,7 @@

Examples Gallery

autocomplete="off" spellcheck="false" aria-label="Search examples" /> - 62 examples + 64 examples
@@ -1006,6 +1006,28 @@

cart

View example
+
+ + park-bench — A procedural wrought-iron park bench through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract. + +
+

park-bench

+

A procedural wrought-iron park bench through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.

+

witnesses Recomputed: 2100 tris, two materials with 510 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.080×0.566×0.853 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.

+ View example +
+
+
+ + wheelbarrow — A procedural wooden wheelbarrow through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract. + +
+

wheelbarrow

+

A procedural wooden wheelbarrow through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.

+

witnesses Recomputed: 3088 tris, two materials with 308 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.418×0.463×0.594 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.

+ View example +
+
diff --git a/docs/gallery/park-bench/index.html b/docs/gallery/park-bench/index.html new file mode 100644 index 0000000..a7246da --- /dev/null +++ b/docs/gallery/park-bench/index.html @@ -0,0 +1,1080 @@ + + + + + + park-bench — Examples — Blender Developer Tools + + + + + + + + + + + + + + + + + +
+ Examples Gallery +
+ GitHub +
+
+
+

park-bench

+

A procedural wrought-iron park bench through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.

+
+
+ +

Rendered headless by the example itself — click to zoom.

+
witnesses Recomputed: 2100 tris, two materials with 510 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.080×0.566×0.853 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.
+
+ 
blender --background --python showcase/park-bench/park_bench.py --
+ +
+
+

A showcase piece, not an example. Procedural wrought-iron park bench (scrolled legs, slatted seat and back, armrests) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

+

It asserts budget conformance of the generated result. It does not witness an API contract. "It rendered without error" is not a check.

+

Composes skills mesh-editing-and-bmesh, bake-high-to-low, depsgraph-and-evaluated-data, engine-export-presets, and snippets bake_normal_high_to_low.py, setup_bake_target_image.py, lod_chain.py / decimate_to_budget.py, convex_hull_collider.py, export_preset_unity.py (helpers copied, not imported as a package).

+

Budgets

+

Declared as named constants; every gate recomputes from the mesh, materials, UVs, evaluated LOD, collider, or export file.

+

| Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) | | --- | --- | --- | | Base triangles | 2000–2200 | 2100 / 2100 / 2100 | | LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.4952 | | LOD2 ratio | 0.10–0.35 of base | 0.2200 / 0.2200 / 0.1400 | | Materials | exactly 2 distinct, ≥48 metal faces | 2 slots, 510 metal | | UVs | in 0..1, AABB overlap ≤ 1e-5 | in range, overlap 0 | | Outer AABB | (1.080, 0.566, 0.853) m ± 0.01 | (1.0800, 0.5657, 0.8531), zmin 0 | | Collider tris | ≤ 140 | 106 | | Export | written, size > 0 | 159868 / 159868 / 159852 bytes |

+

DECIMATE COLLAPSE triangle counts are not identical across series — 5.2.1 is more aggressive on LOD2. The gate is a ratio band, not an exact count. Bake pixels are stochastic; the gate is has_data plus operator FINISHED, not byte-identity. Construction uses no RNG. Export byte counts differ by 16 B on 5.2.1 (glTF serializer), not a gated axis.

+

--skip-decimate skips the LOD DECIMATE stage so LOD1 ratio is 1.0 and exit 9 fires. That is the named budget the falsifier violates.

+

Run

+
blender --background --python park_bench.py --
+blender --background --python park_bench.py -- --skip-decimate
+blender --background --python park_bench.py -- --output bench.png
+

Smoke does not pass --output or --skip-decimate.

+

Exit codes

+

File-local. 9 is a valid check code. 10 is reserved for gallery_framing.check_framing on the --output path.

+

| Code | Meaning | | --- | --- | | 0 | Success | | 1 | Uncaught exception (FATAL wrapper) | | 2 | argparse / usage | | 3 | Mesh did not build / no UV layer | | 4 | Base triangle count outside range | | 5 | Material count ≠ 2 distinct slots, or wood/metal faces missing | | 6 | UVs outside 0..1 | | 7 | UV AABB overlap above tolerance | | 8 | World AABB off declared outer size | | 9 | LOD ratio band (--skip-decimate lands here) | | 10 | Framing gate (render path only) | | 11 | Collider triangle count above ceiling | | 12 | Bake did not finish or image has no data | | 13 | Export file missing or empty | | 14 | --output produced no file |

+
+
+

Source

+
+ showcase/park-bench/park_bench.py + View on GitHub → +
+ 
"""Game-ready park bench — a showcase piece, not an example.
+
+Asserts budget conformance of a procedural wrought-iron bench (scrolled
+legs, slatted seat and back) after composing shipped pipeline pieces:
+bmesh construction, UVs, two materials, high-to-low normal bake, LOD
+chain, convex collider, Unity glTF export.
+
+Budgets are declared below and recomputed from the generated result.
+They are not API-contract witnesses. ``--skip-decimate`` skips the LOD
+DECIMATE stage so the LOD-ratio budget fails.
+
+No RNG. Construction is closed-form. DECIMATE COLLAPSE triangle counts
+are not byte-identical across Blender versions — the LOD gate is a
+ratio band, not an exact count.
+
+    blender --background --python park_bench.py --
+    blender --background --python park_bench.py -- --skip-decimate
+    blender --background --python park_bench.py -- --output bench.png
+"""
+import argparse
+import math
+import os
+import sys
+import tempfile
+import traceback
+
+import bmesh
+import bpy
+from mathutils import Euler, Vector
+
+_REPO = os.path.abspath(
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir, os.pardir)
+)
+sys.path.insert(0, os.path.join(_REPO, "examples"))
+sys.dont_write_bytecode = True
+import gallery_framing  # noqa: E402
+
+SEAT_W = 1.18
+SEAT_D = 0.46
+SEAT_Z = 0.44
+N_SEAT = 6
+N_BACK = 4
+SLAT_T = 0.032
+BACK_H = 0.40
+IRON_T = 0.026
+SCROLL_R = 0.10
+SCROLL_N = 12
+ARM_Z = 0.62
+
+BBOX_TOL = 0.01
+OUTER_SIZE = (1.080, 0.566, 0.853)
+BASE_TRIS_MIN = 2000
+BASE_TRIS_MAX = 2200
+LOD1_RATIO_MIN = 0.32
+LOD1_RATIO_MAX = 0.62
+LOD2_RATIO_MIN = 0.10
+LOD2_RATIO_MAX = 0.35
+LOD1_TARGET = 0.50
+LOD2_TARGET = 0.22
+MATERIAL_COUNT = 2
+UV_EPS = 1e-4
+UV_OVERLAP_MAX = 1e-5
+COLLIDER_TRIS_MAX = 140
+BAKE_RES = 256
+CAGE_EXTRUSION = 0.08
+METAL_FACES_MIN = 48
+WOOD_FACES_MIN = 24
+
+WOOD_IDX = 0
+METAL_IDX = 1
+
+
+def eevee_engine_id():
+    return "BLENDER_EEVEE" if bpy.app.version >= (5, 0, 0) else "BLENDER_EEVEE_NEXT"
+
+
+def fail(msg, code):
+    print(f"ERROR: {msg}", file=sys.stderr)
+    return code
+
+
+def triangle_count(mesh):
+    mesh.calc_loop_triangles()
+    return len(mesh.loop_triangles)
+
+
+def evaluated_triangle_count(obj):
+    depsgraph = bpy.context.evaluated_depsgraph_get()
+    eval_obj = obj.evaluated_get(depsgraph)
+    eval_mesh = eval_obj.to_mesh()
+    try:
+        eval_mesh.calc_loop_triangles()
+        return len(eval_mesh.loop_triangles)
+    finally:
+        eval_obj.to_mesh_clear()
+
+
+def deselect_all():
+    for ob in list(bpy.context.view_layer.objects):
+        if ob is None:
+            continue
+        ob.select_set(False)
+
+
+def add_box(bm, loc, scale, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cube(bm, size=1.0)
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        p = Vector((v.co.x * scale[0], v.co.y * scale[1], v.co.z * scale[2]))
+        v.co = rot @ p + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_oriented_box(bm, a, b, scale_xy, mat_idx):
+    a = Vector(a)
+    b = Vector(b)
+    delta = b - a
+    length = delta.length
+    if length < 1e-8:
+        return []
+    quat = Vector((0.0, 0.0, 1.0)).rotation_difference(delta.normalized())
+    eul = quat.to_euler("XYZ")
+    return add_box(
+        bm,
+        ((a + b) * 0.5),
+        (scale_xy[0], scale_xy[1], length),
+        mat_idx,
+        euler=(eul.x, eul.y, eul.z),
+    )
+
+
+def add_arc_yz(bm, x, cy, cz, radius, a0, a1, n, thick, mat_idx):
+    pts = []
+    for i in range(n + 1):
+        t = i / n
+        ang = a0 + (a1 - a0) * t
+        pts.append((x, cy + radius * math.cos(ang), cz + radius * math.sin(ang)))
+    verts = []
+    for p0, p1 in zip(pts, pts[1:]):
+        verts.extend(add_oriented_box(bm, p0, p1, (thick, thick), mat_idx))
+    return verts
+
+
+def pack_uvs(bm, margin=0.08):
+    uv = bm.loops.layers.uv.new("UVMap")
+    faces = list(bm.faces)
+    n = len(faces)
+    cols = max(1, math.ceil(math.sqrt(n)))
+    rows = max(1, math.ceil(n / cols))
+    cell_w = 1.0 / cols
+    cell_h = 1.0 / rows
+    pad_u = margin * cell_w * 0.5
+    pad_v = margin * cell_h * 0.5
+    usable_w = cell_w - 2.0 * pad_u
+    usable_h = cell_h - 2.0 * pad_v
+    for i, face in enumerate(faces):
+        col = i % cols
+        row = i // cols
+        nrm = face.normal
+        ax = abs(nrm.x)
+        ay = abs(nrm.y)
+        az = abs(nrm.z)
+        coords = []
+        for loop in face.loops:
+            co = loop.vert.co
+            if az >= ax and az >= ay:
+                coords.append((co.x, co.y))
+            elif ax >= ay:
+                coords.append((co.y, co.z))
+            else:
+                coords.append((co.x, co.z))
+        xs = [c[0] for c in coords]
+        ys = [c[1] for c in coords]
+        minx, maxx = min(xs), max(xs)
+        miny, maxy = min(ys), max(ys)
+        dx = max(maxx - minx, 1e-8)
+        dy = max(maxy - miny, 1e-8)
+        origin_u = col * cell_w + pad_u
+        origin_v = row * cell_h + pad_v
+        for loop, (x, y) in zip(face.loops, coords):
+            loop[uv].uv = (
+                origin_u + (x - minx) / dx * usable_w,
+                origin_v + (y - miny) / dy * usable_h,
+            )
+
+
+def build_bench_mesh(name, bevel_offset, bevel_segments):
+    bm = bmesh.new()
+    try:
+        wood = []
+        hx = SEAT_W / 2.0 - 0.08
+        hy = SEAT_D / 2.0 - 0.05
+        # Span past the post centers (±hx) so slats insert into the iron frame.
+        slat_span = 2.0 * hx + IRON_T
+        usable = SEAT_D - 0.08
+        slat_w = usable / N_SEAT
+        y0 = -hy + slat_w / 2.0 + 0.01
+        for i in range(N_SEAT):
+            y = y0 + i * slat_w
+            wood.extend(
+                add_box(
+                    bm,
+                    (0.0, y, SEAT_Z + SLAT_T / 2.0),
+                    (slat_span, slat_w * 0.78, SLAT_T),
+                    WOOD_IDX,
+                )
+            )
+        for i in range(N_BACK):
+            z = SEAT_Z + SLAT_T + 0.05 + i * (BACK_H / N_BACK)
+            wood.extend(
+                add_box(
+                    bm,
+                    (0.0, hy, z),
+                    (slat_span, SLAT_T, slat_w * 0.72),
+                    WOOD_IDX,
+                )
+            )
+
+        if bevel_offset > 0.0:
+            edges = list({e for v in wood for e in v.link_edges})
+            ret = bmesh.ops.bevel(
+                bm,
+                geom=edges,
+                offset=bevel_offset,
+                segments=bevel_segments,
+                profile=0.5,
+                affect="EDGES",
+                clamp_overlap=True,
+            )
+            for f in ret.get("faces") or []:
+                f.material_index = WOOD_IDX
+
+        t = IRON_T
+        add_box(bm, (0.0, -hy, SEAT_Z - 0.018), (SEAT_W - 0.10, t * 1.15, t), METAL_IDX)
+        add_box(bm, (0.0, hy, SEAT_Z - 0.018), (SEAT_W - 0.10, t * 1.15, t), METAL_IDX)
+        for xsign in (-1.0, 1.0):
+            add_box(
+                bm,
+                (xsign * hx, 0.0, SEAT_Z - 0.018),
+                (t * 1.15, SEAT_D - 0.08, t),
+                METAL_IDX,
+            )
+
+        back_top = SEAT_Z + SLAT_T + BACK_H + 0.02
+        for xsign in (-1.0, 1.0):
+            x = xsign * hx
+            add_oriented_box(
+                bm, (x, hy, SEAT_Z), (x, hy, back_top), (t, t), METAL_IDX
+            )
+            add_oriented_box(
+                bm, (x, -hy, SEAT_Z), (x, -hy, ARM_Z), (t, t), METAL_IDX
+            )
+            add_oriented_box(
+                bm, (x, -hy, ARM_Z), (x, hy, ARM_Z), (t * 0.9, t * 0.9), METAL_IDX
+            )
+            add_oriented_box(
+                bm,
+                (x, -hy, SCROLL_R + 0.02),
+                (x, -hy, SEAT_Z),
+                (t, t),
+                METAL_IDX,
+            )
+            add_oriented_box(
+                bm,
+                (x, hy, SCROLL_R + 0.02),
+                (x, hy, SEAT_Z),
+                (t, t),
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                -hy + 0.01,
+                SCROLL_R,
+                SCROLL_R,
+                math.pi / 2.0,
+                math.pi + 0.45,
+                SCROLL_N,
+                t,
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                hy - 0.01,
+                SCROLL_R,
+                SCROLL_R,
+                math.pi / 2.0,
+                -0.45,
+                SCROLL_N,
+                t,
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                -hy - 0.02,
+                ARM_Z - 0.04,
+                0.07,
+                math.pi * 0.15,
+                math.pi * 0.95,
+                10,
+                t * 0.85,
+                METAL_IDX,
+            )
+
+        add_box(bm, (0.0, hy, back_top), (SEAT_W - 0.12, t, t), METAL_IDX)
+        add_box(bm, (0.0, 0.0, 0.18), (SEAT_W - 0.22, t * 0.9, t * 0.9), METAL_IDX)
+        add_box(bm, (0.0, 0.0, 0.18), (t * 0.9, SEAT_D - 0.14, t * 0.9), METAL_IDX)
+
+        xs = [v.co.x for v in bm.verts]
+        ys = [v.co.y for v in bm.verts]
+        zs = [v.co.z for v in bm.verts]
+        cx = 0.5 * (min(xs) + max(xs))
+        cy = 0.5 * (min(ys) + max(ys))
+        zmin = min(zs)
+        for v in bm.verts:
+            v.co.x -= cx
+            v.co.y -= cy
+            v.co.z -= zmin
+            if v.co.z < 0.0:
+                v.co.z = 0.0
+
+        pack_uvs(bm)
+        bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
+        for face in bm.faces:
+            face.smooth = False
+        me = bpy.data.meshes.new(name)
+        bm.to_mesh(me)
+        me.update()
+        for poly in me.polygons:
+            poly.use_smooth = False
+    finally:
+        bm.free()
+    out = bpy.data.objects.new(name, me)
+    bpy.context.collection.objects.link(out)
+    return out
+
+
+def principled(name, color, metallic, roughness):
+    mat = bpy.data.materials.new(name)
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes["Principled BSDF"]
+    bsdf.inputs["Base Color"].default_value = color
+    bsdf.inputs["Metallic"].default_value = metallic
+    bsdf.inputs["Roughness"].default_value = roughness
+    return mat
+
+
+def assign_slots(obj, wood, metal):
+    mats = obj.data.materials
+    wanted = (wood, metal)
+    for i, mat in enumerate(wanted):
+        if i < len(mats):
+            mats[i] = mat
+        else:
+            mats.append(mat)
+
+
+def world_bbox(obj):
+    corners = [obj.matrix_world @ Vector(c) for c in obj.bound_box]
+    xs = [c.x for c in corners]
+    ys = [c.y for c in corners]
+    zs = [c.z for c in corners]
+    return (min(xs), min(ys), min(zs), max(xs), max(ys), max(zs))
+
+
+def uv_stats(mesh):
+    uv = mesh.uv_layers.active
+    if uv is None:
+        return 0.0, 0.0, 1.0, 1.0, 0, 1.0
+    data = uv.data
+    us = [loop.uv[0] for loop in data]
+    vs = [loop.uv[1] for loop in data]
+    aabbs = []
+    for poly in mesh.polygons:
+        pu = [data[i].uv[0] for i in poly.loop_indices]
+        pv = [data[i].uv[1] for i in poly.loop_indices]
+        aabbs.append((min(pu), min(pv), max(pu), max(pv)))
+    overlap = 0.0
+    for i in range(len(aabbs)):
+        a = aabbs[i]
+        for j in range(i + 1, len(aabbs)):
+            b = aabbs[j]
+            x0 = max(a[0], b[0])
+            y0 = max(a[1], b[1])
+            x1 = min(a[2], b[2])
+            y1 = min(a[3], b[3])
+            overlap += max(0.0, x1 - x0) * max(0.0, y1 - y0)
+    return min(us), min(vs), max(us), max(vs), overlap, len(aabbs)
+
+
+def make_lod(obj, name, ratio, skip_decimate):
+    mesh = obj.data.copy()
+    lod = bpy.data.objects.new(name, mesh)
+    lod.matrix_world = obj.matrix_world.copy()
+    bpy.context.scene.collection.objects.link(lod)
+    if not skip_decimate and 0.0 < ratio < 1.0:
+        mod = lod.modifiers.new("DecimateBudget", "DECIMATE")
+        mod.decimate_type = "COLLAPSE"
+        mod.ratio = ratio
+    return lod
+
+
+def convex_hull_collider(obj, name):
+    mesh = bpy.data.meshes.new(name)
+    bm = bmesh.new()
+    try:
+        bm.from_mesh(obj.data)
+        result = bmesh.ops.convex_hull(bm, input=list(bm.verts))
+        interior = result.get("geom_interior") or []
+        unused = result.get("geom_unused") or []
+        if interior:
+            bmesh.ops.delete(bm, geom=interior, context="VERTS")
+        if unused:
+            bmesh.ops.delete(bm, geom=unused, context="VERTS")
+        bm.to_mesh(mesh)
+        mesh.update()
+    finally:
+        bm.free()
+    collider = bpy.data.objects.new(name, mesh)
+    bpy.context.collection.objects.link(collider)
+    collider.matrix_world = obj.matrix_world.copy()
+    return collider
+
+
+def setup_bake_image(obj, target_mat, size=BAKE_RES):
+    if not obj.data.uv_layers:
+        return None, None
+    img = bpy.data.images.new("BenchNrm", size, size, alpha=True, float_buffer=False)
+    img.colorspace_settings.name = "Non-Color"
+    nodes = target_mat.node_tree.nodes
+    tex = nodes.new("ShaderNodeTexImage")
+    tex.image = img
+    nodes.active = tex
+    tex.select = True
+    obj.active_material_index = WOOD_IDX
+    return img, tex
+
+
+def bake_normal(high, low):
+    scene = bpy.context.scene
+    scene.render.engine = "CYCLES"
+    scene.cycles.device = "CPU"
+    scene.cycles.samples = 1
+    scene.cycles.use_denoising = False
+    deselect_all()
+    high.select_set(True)
+    low.select_set(True)
+    bpy.context.view_layer.objects.active = low
+    return bpy.ops.object.bake(
+        type="NORMAL",
+        use_selected_to_active=True,
+        cage_extrusion=CAGE_EXTRUSION,
+        use_cage=False,
+        normal_space="TANGENT",
+        margin=4,
+        margin_type="ADJACENT_FACES",
+        use_clear=True,
+        target="IMAGE_TEXTURES",
+    )
+
+
+def export_unity(path, objects):
+    deselect_all()
+    for ob in objects:
+        ob.select_set(True)
+    bpy.context.view_layer.objects.active = objects[0]
+    bpy.ops.export_scene.gltf(
+        filepath=path,
+        use_selection=True,
+        export_yup=True,
+        export_apply=True,
+        export_draco_mesh_compression_enable=False,
+        export_animations=False,
+    )
+
+
+def check(skip_decimate):
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    low = build_bench_mesh("BenchLow", bevel_offset=0.005, bevel_segments=2)
+    high = build_bench_mesh("BenchHigh", bevel_offset=0.005, bevel_segments=4)
+    wood = principled("BenchWood", (0.40, 0.20, 0.07, 1.0), 0.0, 0.58)
+    metal = principled("BenchIron", (0.09, 0.095, 0.11, 1.0), 1.0, 0.28)
+    assign_slots(low, wood, metal)
+    assign_slots(high, wood, metal)
+
+    if low.data is None or len(low.data.polygons) < 6:
+        return fail("bench mesh did not build", 3), None, None, None, None, None
+
+    base_tris = triangle_count(low.data)
+    mats = [s for s in low.data.materials if s is not None]
+    nmat = len(mats)
+    distinct_mats = len({id(s) for s in mats})
+    idx_counts = {}
+    for poly in low.data.polygons:
+        idx_counts[poly.material_index] = idx_counts.get(poly.material_index, 0) + 1
+    print(f"measured mat_index_counts={idx_counts}")
+    u0, v0, u1, v1, overlap, nfaces = uv_stats(low.data)
+    bb = world_bbox(low)
+    size_x = bb[3] - bb[0]
+    size_y = bb[4] - bb[1]
+    size_z = bb[5] - bb[2]
+
+    img, tex = setup_bake_image(low, wood)
+    if img is None:
+        return fail("bench has no UV layer", 3), None, None, None, None, None
+    bake_result = bake_normal(high, low)
+
+    lod1 = make_lod(low, "BenchLOD1", LOD1_TARGET, skip_decimate)
+    lod2 = make_lod(low, "BenchLOD2", LOD2_TARGET, skip_decimate)
+    bpy.context.view_layer.update()
+    lod1_tris = evaluated_triangle_count(lod1)
+    lod2_tris = evaluated_triangle_count(lod2)
+    r1 = lod1_tris / base_tris if base_tris else 0.0
+    r2 = lod2_tris / base_tris if base_tris else 0.0
+
+    collider_src = build_bench_mesh("BenchColSrc", bevel_offset=0.0, bevel_segments=1)
+    collider = convex_hull_collider(collider_src, "BenchCollider")
+    bpy.data.objects.remove(collider_src, do_unlink=True)
+    col_tris = triangle_count(collider.data)
+
+    export_path = os.path.join(
+        tempfile.gettempdir(),
+        f"bdt_park_bench_{os.getpid()}.glb",
+    )
+    if os.path.exists(export_path):
+        os.remove(export_path)
+    export_unity(export_path, [low, collider])
+    export_size = os.path.getsize(export_path) if os.path.isfile(export_path) else 0
+
+    print(f"blender={tuple(bpy.app.version)} skip_decimate={skip_decimate}")
+    print(
+        f"measured base_tris={base_tris} lod1_tris={lod1_tris} "
+        f"lod2_tris={lod2_tris} r1={r1:.4f} r2={r2:.4f}"
+    )
+    print(
+        f"measured nmat={nmat} uv=({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f}) "
+        f"overlap={overlap:.6f} nfaces={nfaces}"
+    )
+    print(
+        f"measured bbox=({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+        f"outer={OUTER_SIZE} zmin={bb[2]:.4f}"
+    )
+    print(
+        f"measured collider_tris={col_tris} bake={bake_result} "
+        f"bake_has_data={img.has_data} export_bytes={export_size}"
+    )
+
+    if not (BASE_TRIS_MIN <= base_tris <= BASE_TRIS_MAX):
+        return fail(
+            f"base tris {base_tris} not in [{BASE_TRIS_MIN}, {BASE_TRIS_MAX}]",
+            4,
+        ), None, None, None, None, None
+    if nmat != MATERIAL_COUNT or distinct_mats != MATERIAL_COUNT:
+        return fail(
+            f"material slots {nmat} distinct {distinct_mats} != {MATERIAL_COUNT}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(METAL_IDX, 0) < METAL_FACES_MIN:
+        return fail(
+            f"metal faces {idx_counts.get(METAL_IDX, 0)} < {METAL_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(WOOD_IDX, 0) < WOOD_FACES_MIN:
+        return fail(
+            f"wood faces {idx_counts.get(WOOD_IDX, 0)} < {WOOD_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if u0 < -UV_EPS or v0 < -UV_EPS or u1 > 1.0 + UV_EPS or v1 > 1.0 + UV_EPS:
+        return fail(
+            f"UVs outside 0..1: ({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f})",
+            6,
+        ), None, None, None, None, None
+    if overlap > UV_OVERLAP_MAX:
+        return fail(
+            f"UV AABB overlap {overlap:.6f} > {UV_OVERLAP_MAX}",
+            7,
+        ), None, None, None, None, None
+    if (
+        abs(size_x - OUTER_SIZE[0]) > BBOX_TOL
+        or abs(size_y - OUTER_SIZE[1]) > BBOX_TOL
+        or abs(size_z - OUTER_SIZE[2]) > BBOX_TOL
+    ):
+        return fail(
+            f"bbox ({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+            f"off outer {OUTER_SIZE}",
+            8,
+        ), None, None, None, None, None
+    if not (LOD1_RATIO_MIN <= r1 <= LOD1_RATIO_MAX):
+        return fail(
+            f"LOD1 ratio {r1:.4f} not in [{LOD1_RATIO_MIN}, {LOD1_RATIO_MAX}] "
+            "(--skip-decimate is the designed fail)",
+            9,
+        ), None, None, None, None, None
+    if not (LOD2_RATIO_MIN <= r2 <= LOD2_RATIO_MAX):
+        return fail(
+            f"LOD2 ratio {r2:.4f} not in [{LOD2_RATIO_MIN}, {LOD2_RATIO_MAX}]",
+            9,
+        ), None, None, None, None, None
+    if col_tris > COLLIDER_TRIS_MAX:
+        return fail(
+            f"collider tris {col_tris} > {COLLIDER_TRIS_MAX}",
+            11,
+        ), None, None, None, None, None
+    if bake_result != {"FINISHED"} or not img.has_data:
+        return fail(
+            f"bake failed result={bake_result} has_data={img.has_data}",
+            12,
+        ), None, None, None, None, None
+    if export_size <= 0:
+        return fail("export file missing or empty", 13), None, None, None, None, None
+    return 0, low, high, wood, tex, collider
+
+
+def wire_normal(mat, tex):
+    nt = mat.node_tree
+    bsdf = nt.nodes["Principled BSDF"]
+    nrm = nt.nodes.new("ShaderNodeNormalMap")
+    nrm.inputs["Strength"].default_value = 1.0
+    nt.links.new(tex.outputs["Color"], nrm.inputs["Color"])
+    nt.links.new(nrm.outputs["Normal"], bsdf.inputs["Normal"])
+
+
+def render_still(low, wood, tex, path, engine):
+    scene = bpy.context.scene
+    wire_normal(wood, tex)
+    for ob in list(scene.objects):
+        if ob.type == "MESH" and ob != low:
+            ob.hide_render = True
+            ob.hide_viewport = True
+
+    low.rotation_euler.z = math.radians(-14.0)
+    low.rotation_euler.x = math.radians(2.0)
+
+    floor_me = bpy.data.meshes.new("Floor")
+    bm = bmesh.new()
+    try:
+        bmesh.ops.create_grid(bm, x_segments=1, y_segments=1, size=14.0)
+        bm.to_mesh(floor_me)
+    finally:
+        bm.free()
+    fmat = bpy.data.materials.new("Floor")
+    fmat.use_nodes = True
+    fb = fmat.node_tree.nodes["Principled BSDF"]
+    fb.inputs["Base Color"].default_value = (0.03, 0.032, 0.037, 1.0)
+    fb.inputs["Roughness"].default_value = 0.7
+    floor_me.materials.append(fmat)
+    floor = bpy.data.objects.new("Floor", floor_me)
+    scene.collection.objects.link(floor)
+    wall = bpy.data.objects.new("Wall", floor_me.copy())
+    wall.location = (0.0, 8.5, 0.0)
+    wall.rotation_euler = (math.radians(90), 0.0, 0.0)
+    scene.collection.objects.link(wall)
+
+    world = bpy.data.worlds.new("World")
+    world.use_nodes = True
+    world.node_tree.nodes["Background"].inputs["Color"].default_value = (
+        0.02, 0.021, 0.025, 1.0,
+    )
+    scene.world = world
+
+    def light(name, loc, energy, size, col, rot):
+        ld = bpy.data.lights.new(name, "AREA")
+        ld.energy = energy
+        ld.size = size
+        ld.color = col
+        ob = bpy.data.objects.new(name, ld)
+        ob.location = loc
+        ob.rotation_euler = tuple(math.radians(a) for a in rot)
+        scene.collection.objects.link(ob)
+
+    light("Key", (-3.6, -5.0, 5.4), 660.0, 4.0, (1.0, 0.94, 0.86), (50, 0, -36))
+    light("Fill", (5.0, -3.4, 2.4), 46.0, 8.0, (0.72, 0.82, 1.0), (62, 0, 50))
+    light("Wedge", (2.2, 4.0, 3.8), 600.0, 5.5, (1.0, 0.70, 0.40), (-70, 0, 198))
+
+    cam_data = bpy.data.cameras.new("Cam")
+    cam_data.lens = 50.0
+    cam = bpy.data.objects.new("Cam", cam_data)
+    cam.location = (1.95, -2.55, 1.22)
+    scene.collection.objects.link(cam)
+    aim = bpy.data.objects.new("Aim", None)
+    aim.location = (0.0, 0.0, 0.40)
+    scene.collection.objects.link(aim)
+    con = cam.constraints.new("TRACK_TO")
+    con.target = aim
+    con.track_axis = "TRACK_NEGATIVE_Z"
+    con.up_axis = "UP_Y"
+    scene.camera = cam
+
+    scene.render.engine = "CYCLES" if engine == "cycles" else eevee_engine_id()
+    if engine == "cycles":
+        scene.cycles.samples = 32
+        scene.cycles.device = "CPU"
+    else:
+        try:
+            scene.eevee.taa_render_samples = 64
+        except AttributeError:
+            pass
+    scene.render.resolution_x = 1280
+    scene.render.resolution_y = 720
+    scene.render.image_settings.file_format = (
+        "WEBP" if path.lower().endswith(".webp") else "PNG"
+    )
+    if path.lower().endswith(".webp"):
+        scene.render.image_settings.quality = 90
+    scene.render.filepath = path
+    scene.view_settings.view_transform = "Standard"
+
+    fcode = gallery_framing.check_framing(
+        scene, cam, hero=[low], elements=[low], stage=[floor, wall],
+    )
+    if fcode:
+        return fcode
+    bpy.ops.render.render(write_still=True)
+    if not (os.path.exists(path) and os.path.getsize(path) > 0):
+        return fail("render produced no file", 14)
+    return 0
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    p = argparse.ArgumentParser()
+    p.add_argument("--output", default=None)
+    p.add_argument("--engine", default="eevee", choices=("eevee", "cycles"))
+    p.add_argument(
+        "--skip-decimate",
+        action="store_true",
+        help="falsification: skip the LOD DECIMATE stage",
+    )
+    args = p.parse_args(argv)
+
+    code, low, _high, wood, tex, _col = check(args.skip_decimate)
+    if code:
+        return code
+    if args.output:
+        rcode = render_still(low, wood, tex, os.path.abspath(args.output), args.engine)
+        if rcode:
+            return rcode
+        print(f"rendered still {args.output}")
+    print("park-bench OK")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except Exception as e:
+        traceback.print_exc()
+        print(f"FATAL: {e}", file=sys.stderr)
+        sys.exit(1)
+
+
+
+ +
+
+ generated from examples/gallery.json + CC-BY-NC-ND-4.0 + exit 0 +
+
+ + + diff --git a/docs/gallery/watchtower/index.html b/docs/gallery/watchtower/index.html index 723449d..f036db6 100644 --- a/docs/gallery/watchtower/index.html +++ b/docs/gallery/watchtower/index.html @@ -285,7 +285,7 @@

Source

"""Game-ready timber watchtower — a showcase piece, not an example.
 
 Asserts budget conformance of a procedural lookout (posts, braces,
-platform, ladder, pyramidal roof) after composing shipped pipeline
+platform, hatch ladder, coursed shake roof) after composing shipped pipeline
 pieces: bmesh construction, UVs, three materials, high-to-low normal
 bake, LOD chain, convex collider, Unity glTF export.
 
diff --git a/docs/gallery/wheelbarrow/index.html b/docs/gallery/wheelbarrow/index.html
new file mode 100644
index 0000000..0cf5734
--- /dev/null
+++ b/docs/gallery/wheelbarrow/index.html
@@ -0,0 +1,1201 @@
+
+
+
+  
+  
+  wheelbarrow — Examples — Blender Developer Tools
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  
+
+
+  
+  

+     Examples Gallery
+    

+      GitHub
+    

+  

+  

+    
wheelbarrow

+    
A procedural wooden wheelbarrow through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.

+  

+  

+    
+    
Rendered headless by the example itself — click to zoom.

+    
witnesses Recomputed: 3088 tris, two materials with 308 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.418×0.463×0.594 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.

+    

+      
blender --background --python showcase/wheelbarrow/wheelbarrow.py --

+      
+    

+    

+
A showcase piece, not an example. Procedural wooden wheelbarrow (staved U-tray, iron straps, single spoked wheel, rear legs, handles) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

+
It asserts budget conformance of the generated result. It does not witness an API contract. "It rendered without error" is not a check.

+
Composes skills mesh-editing-and-bmesh, bake-high-to-low, depsgraph-and-evaluated-data, engine-export-presets, and snippets bake_normal_high_to_low.py, setup_bake_target_image.py, lod_chain.py / decimate_to_budget.py, convex_hull_collider.py, export_preset_unity.py (helpers copied, not imported as a package).

+
Budgets

+
Declared as named constants; every gate recomputes from the mesh, materials, UVs, evaluated LOD, collider, or export file.

+
| Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) | | --- | --- | --- | | Base triangles | 2980–3200 | 3088 / 3088 / 3088 | | LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.5000 | | LOD2 ratio | 0.10–0.35 of base | 0.2196 / 0.2196 / 0.2014 | | Materials | exactly 2 distinct, ≥24 metal faces | 2 slots, 308 metal | | UVs | in 0..1, AABB overlap ≤ 1e-5 | in range, overlap 0 | | Outer AABB | (1.418, 0.463, 0.594) m ± 0.01 | (1.4176, 0.4627, 0.5937), zmin 0 | | Collider tris | ≤ 140 | 106 | | Export | written, size > 0 | 227404 / 227404 / 227388 bytes |

+
DECIMATE COLLAPSE triangle counts are not identical across series — 5.2.1 is more aggressive on LOD2. The gate is a ratio band, not an exact count. Bake pixels are stochastic; the gate is has_data plus operator FINISHED, not byte-identity. Construction uses no RNG. Export byte counts differ by 16 B on 5.2.1 (glTF serializer), not a gated axis.

+
--skip-decimate skips the LOD DECIMATE stage so LOD1 ratio is 1.0 and exit 9 fires. That is the named budget the falsifier violates.

+
Run

+
blender --background --python wheelbarrow.py --
+blender --background --python wheelbarrow.py -- --skip-decimate
+blender --background --python wheelbarrow.py -- --output barrow.png

+
Smoke does not pass --output or --skip-decimate.

+
Exit codes

+
File-local. 9 is a valid check code. 10 is reserved for gallery_framing.check_framing on the --output path.

+
| Code | Meaning | | --- | --- | | 0 | Success | | 1 | Uncaught exception (FATAL wrapper) | | 2 | argparse / usage | | 3 | Mesh did not build / no UV layer | | 4 | Base triangle count outside range | | 5 | Material count ≠ 2 distinct slots, or wood/metal faces missing | | 6 | UVs outside 0..1 | | 7 | UV AABB overlap above tolerance | | 8 | World AABB off declared outer size | | 9 | LOD ratio band (--skip-decimate lands here) | | 10 | Framing gate (render path only) | | 11 | Collider triangle count above ceiling | | 12 | Bake did not finish or image has no data | | 13 | Export file missing or empty | | 14 | --output produced no file |

+    

+    

+      
Source

+      

+        showcase/wheelbarrow/wheelbarrow.py
+        View on GitHub →
+      

+      
"""Game-ready wooden wheelbarrow — a showcase piece, not an example.
+
+Asserts budget conformance of a procedural wheelbarrow (staved U-tray,
+iron straps, single spoked wheel, rear legs, handles) after composing
+shipped pipeline pieces: bmesh construction, UVs, two materials,
+high-to-low normal bake, LOD chain, convex collider, Unity glTF export.
+
+Budgets are declared below and recomputed from the generated result.
+They are not API-contract witnesses. ``--skip-decimate`` skips the LOD
+DECIMATE stage so the LOD-ratio budget fails.
+
+No RNG. Construction is closed-form. DECIMATE COLLAPSE triangle counts
+are not byte-identical across Blender versions — the LOD gate is a
+ratio band, not an exact count.
+
+    blender --background --python wheelbarrow.py --
+    blender --background --python wheelbarrow.py -- --skip-decimate
+    blender --background --python wheelbarrow.py -- --output barrow.png
+"""
+import argparse
+import math
+import os
+import sys
+import tempfile
+import traceback
+
+import bmesh
+import bpy
+from mathutils import Euler, Vector
+
+_REPO = os.path.abspath(
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir, os.pardir)
+)
+sys.path.insert(0, os.path.join(_REPO, "examples"))
+sys.dont_write_bytecode = True
+import gallery_framing  # noqa: E402
+
+RIM_MAJOR = 0.155
+RIM_MINOR = 0.020
+HUB_R = 0.028
+HUB_W = 0.038
+N_SPOKES = 8
+SPOKE_T = 0.014
+TRAY_L = 0.70
+TRAY_R = 0.205
+STAVE_T = 0.028
+N_STAVES = 7
+A_SPAN = 1.38
+HANDLE_L = 0.50
+IRON_T = 0.014
+
+BBOX_TOL = 0.01
+OUTER_SIZE = (1.418, 0.463, 0.594)
+BASE_TRIS_MIN = 2980
+BASE_TRIS_MAX = 3200
+LOD1_RATIO_MIN = 0.32
+LOD1_RATIO_MAX = 0.62
+LOD2_RATIO_MIN = 0.10
+LOD2_RATIO_MAX = 0.35
+LOD1_TARGET = 0.50
+LOD2_TARGET = 0.22
+MATERIAL_COUNT = 2
+UV_EPS = 1e-4
+UV_OVERLAP_MAX = 1e-5
+COLLIDER_TRIS_MAX = 140
+BAKE_RES = 256
+CAGE_EXTRUSION = 0.08
+METAL_FACES_MIN = 24
+WOOD_FACES_MIN = 24
+
+WOOD_IDX = 0
+METAL_IDX = 1
+
+
+def eevee_engine_id():
+    return "BLENDER_EEVEE" if bpy.app.version >= (5, 0, 0) else "BLENDER_EEVEE_NEXT"
+
+
+def fail(msg, code):
+    print(f"ERROR: {msg}", file=sys.stderr)
+    return code
+
+
+def triangle_count(mesh):
+    mesh.calc_loop_triangles()
+    return len(mesh.loop_triangles)
+
+
+def evaluated_triangle_count(obj):
+    depsgraph = bpy.context.evaluated_depsgraph_get()
+    eval_obj = obj.evaluated_get(depsgraph)
+    eval_mesh = eval_obj.to_mesh()
+    try:
+        eval_mesh.calc_loop_triangles()
+        return len(eval_mesh.loop_triangles)
+    finally:
+        eval_obj.to_mesh_clear()
+
+
+def deselect_all():
+    for ob in list(bpy.context.view_layer.objects):
+        if ob is None:
+            continue
+        ob.select_set(False)
+
+
+def add_box(bm, loc, scale, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cube(bm, size=1.0)
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        p = Vector((v.co.x * scale[0], v.co.y * scale[1], v.co.z * scale[2]))
+        v.co = rot @ p + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_oriented_box(bm, a, b, scale_xy, mat_idx):
+    a = Vector(a)
+    b = Vector(b)
+    delta = b - a
+    length = delta.length
+    if length < 1e-8:
+        return []
+    quat = Vector((0.0, 0.0, 1.0)).rotation_difference(delta.normalized())
+    eul = quat.to_euler("XYZ")
+    return add_box(
+        bm,
+        ((a + b) * 0.5),
+        (scale_xy[0], scale_xy[1], length),
+        mat_idx,
+        euler=(eul.x, eul.y, eul.z),
+    )
+
+
+def add_cyl(bm, loc, radius, depth, segments, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cone(
+        bm,
+        cap_ends=True,
+        cap_tris=False,
+        segments=segments,
+        radius1=radius,
+        radius2=radius,
+        depth=depth,
+    )
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        v.co = rot @ v.co + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_rim(bm, loc, major, minor, mat_idx, euler=(0.0, 0.0, 0.0)):
+    n_major = 16
+    n_minor = 8
+    rings = []
+    for i in range(n_major):
+        u = i * (2.0 * math.pi / n_major)
+        ring = []
+        for j in range(n_minor):
+            v = j * (2.0 * math.pi / n_minor)
+            x = (major + minor * math.cos(v)) * math.cos(u)
+            y = (major + minor * math.cos(v)) * math.sin(u)
+            z = minor * math.sin(v)
+            ring.append(bm.verts.new((x, y, z)))
+        rings.append(ring)
+    bm.verts.ensure_lookup_table()
+    for i in range(n_major):
+        i2 = (i + 1) % n_major
+        for j in range(n_minor):
+            j2 = (j + 1) % n_minor
+            face = bm.faces.new(
+                (rings[i][j], rings[i2][j], rings[i2][j2], rings[i][j2])
+            )
+            face.material_index = mat_idx
+    verts = [v for ring in rings for v in ring]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        v.co = rot @ v.co + origin
+    return verts
+
+
+def add_wheel_wood(bm, loc, wood):
+    wood.extend(
+        add_rim(bm, loc, RIM_MAJOR, RIM_MINOR, WOOD_IDX, euler=(math.pi / 2.0, 0.0, 0.0))
+    )
+    wood.extend(
+        add_cyl(
+            bm,
+            loc,
+            HUB_R,
+            HUB_W,
+            12,
+            WOOD_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    inner = HUB_R + 0.008
+    outer = RIM_MAJOR - RIM_MINOR * 0.55
+    mid_r = 0.5 * (inner + outer)
+    slen = outer - inner
+    for i in range(N_SPOKES):
+        a = i * (2.0 * math.pi / N_SPOKES)
+        dx = math.cos(a)
+        dz = math.sin(a)
+        cx = loc[0] + dx * mid_r
+        cy = loc[1]
+        cz = loc[2] + dz * mid_r
+        wood.extend(
+            add_box(
+                bm,
+                (cx, cy, cz),
+                (slen, SPOKE_T * 0.85, SPOKE_T),
+                WOOD_IDX,
+                euler=(0.0, -a, 0.0),
+            )
+        )
+
+
+def add_wheel_metal(bm, loc, metal):
+    metal.extend(
+        add_rim(
+            bm,
+            loc,
+            RIM_MAJOR + 0.004,
+            RIM_MINOR * 0.45,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    metal.extend(
+        add_cyl(
+            bm,
+            loc,
+            HUB_R + 0.010,
+            0.016,
+            12,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    metal.extend(
+        add_cyl(
+            bm,
+            loc,
+            0.014,
+            0.10,
+            8,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+
+
+def pack_uvs(bm, margin=0.08):
+    uv = bm.loops.layers.uv.new("UVMap")
+    faces = list(bm.faces)
+    n = len(faces)
+    cols = max(1, math.ceil(math.sqrt(n)))
+    rows = max(1, math.ceil(n / cols))
+    cell_w = 1.0 / cols
+    cell_h = 1.0 / rows
+    pad_u = margin * cell_w * 0.5
+    pad_v = margin * cell_h * 0.5
+    usable_w = cell_w - 2.0 * pad_u
+    usable_h = cell_h - 2.0 * pad_v
+    for i, face in enumerate(faces):
+        col = i % cols
+        row = i // cols
+        nrm = face.normal
+        ax = abs(nrm.x)
+        ay = abs(nrm.y)
+        az = abs(nrm.z)
+        coords = []
+        for loop in face.loops:
+            co = loop.vert.co
+            if az >= ax and az >= ay:
+                coords.append((co.x, co.y))
+            elif ax >= ay:
+                coords.append((co.y, co.z))
+            else:
+                coords.append((co.x, co.z))
+        xs = [c[0] for c in coords]
+        ys = [c[1] for c in coords]
+        minx, maxx = min(xs), max(xs)
+        miny, maxy = min(ys), max(ys)
+        dx = max(maxx - minx, 1e-8)
+        dy = max(maxy - miny, 1e-8)
+        origin_u = col * cell_w + pad_u
+        origin_v = row * cell_h + pad_v
+        for loop, (x, y) in zip(face.loops, coords):
+            loop[uv].uv = (
+                origin_u + (x - minx) / dx * usable_w,
+                origin_v + (y - miny) / dy * usable_h,
+            )
+
+
+def build_barrow_mesh(name, bevel_offset, bevel_segments):
+    bm = bmesh.new()
+    try:
+        wood = []
+        metal = []
+        zc = 0.26 + TRAY_R
+        cx = 0.0
+
+        def pt(a, x):
+            return (
+                x,
+                TRAY_R * math.sin(a),
+                zc - TRAY_R * math.cos(a),
+            )
+
+        gap = 0.12
+        for i in range(N_STAVES):
+            t0 = i / N_STAVES
+            t1 = (i + (1.0 - gap)) / N_STAVES
+            a0 = -A_SPAN + 2.0 * A_SPAN * t0
+            a1 = -A_SPAN + 2.0 * A_SPAN * t1
+            mid = 0.5 * (a0 + a1)
+            chord = TRAY_R * abs(a1 - a0) * 0.95
+            wood.extend(
+                add_box(
+                    bm,
+                    pt(mid, cx),
+                    (TRAY_L, chord, STAVE_T),
+                    WOOD_IDX,
+                    euler=(mid, 0.0, 0.0),
+                )
+            )
+            wood.extend(
+                add_box(
+                    bm,
+                    pt(mid, cx + TRAY_L / 2.0 + 0.014),
+                    (0.028, chord * 1.02, STAVE_T * 1.05),
+                    WOOD_IDX,
+                    euler=(mid, 0.0, 0.0),
+                )
+            )
+
+        rim_y = TRAY_R * math.sin(A_SPAN)
+        rim_z = zc - TRAY_R * math.cos(A_SPAN)
+        for ysign in (-1.0, 1.0):
+            start = (
+                cx - TRAY_L / 2.0 + 0.05,
+                ysign * rim_y,
+                rim_z,
+            )
+            end = (
+                cx - TRAY_L / 2.0 - HANDLE_L,
+                ysign * (rim_y + 0.015),
+                0.56,
+            )
+            wood.extend(
+                add_oriented_box(bm, start, end, (0.030, 0.030), WOOD_IDX)
+            )
+
+        lx = cx - TRAY_L * 0.30
+        for ysign in (-1.0, 1.0):
+            top = (lx, ysign * 0.11, zc - TRAY_R * 0.35)
+            bot = (lx - 0.03, ysign * 0.18, 0.02)
+            wood.extend(add_oriented_box(bm, top, bot, (0.034, 0.034), WOOD_IDX))
+        wood.extend(
+            add_oriented_box(
+                bm,
+                (lx, -0.15, 0.13),
+                (lx, 0.15, 0.13),
+                (0.026, 0.026),
+                WOOD_IDX,
+            )
+        )
+
+        if bevel_offset > 0.0:
+            edges = list({e for v in wood for e in v.link_edges})
+            ret = bmesh.ops.bevel(
+                bm,
+                geom=edges,
+                offset=bevel_offset,
+                segments=bevel_segments,
+                profile=0.5,
+                affect="EDGES",
+                clamp_overlap=True,
+            )
+            for f in ret.get("faces") or []:
+                f.material_index = WOOD_IDX
+
+        wx = cx + TRAY_L / 2.0 + 0.04
+        wz = RIM_MAJOR
+        add_wheel_wood(bm, (wx, 0.0, wz), wood)
+        add_wheel_metal(bm, (wx, 0.0, wz), metal)
+
+        r_strap = TRAY_R + STAVE_T * 0.55 + 0.004
+        for sx in (-TRAY_L * 0.28, TRAY_L * 0.22):
+            n = 11
+            pts = []
+            for k in range(n + 1):
+                a = -A_SPAN + 2.0 * A_SPAN * k / n
+                pts.append(
+                    (
+                        cx + sx,
+                        r_strap * math.sin(a),
+                        zc - r_strap * math.cos(a),
+                    )
+                )
+            for p0, p1 in zip(pts, pts[1:]):
+                metal.extend(
+                    add_oriented_box(bm, p0, p1, (0.018, 0.010), METAL_IDX)
+                )
+
+        fy = 0.045
+        for ysign in (-1.0, 1.0):
+            metal.extend(
+                add_oriented_box(
+                    bm,
+                    (cx + TRAY_L / 2.0 - 0.05, ysign * fy, zc - TRAY_R * 0.55),
+                    (wx, ysign * fy, wz),
+                    (0.016, 0.016),
+                    METAL_IDX,
+                )
+            )
+            metal.extend(
+                add_box(
+                    bm,
+                    (lx - 0.03, ysign * 0.18, 0.012),
+                    (0.055, 0.042, 0.022),
+                    METAL_IDX,
+                )
+            )
+
+        xs = [v.co.x for v in bm.verts]
+        ys = [v.co.y for v in bm.verts]
+        zs = [v.co.z for v in bm.verts]
+        rcx = 0.5 * (min(xs) + max(xs))
+        rcy = 0.5 * (min(ys) + max(ys))
+        zmin = min(zs)
+        for v in bm.verts:
+            v.co.x -= rcx
+            v.co.y -= rcy
+            v.co.z -= zmin
+            if v.co.z < 0.0:
+                v.co.z = 0.0
+
+        pack_uvs(bm)
+        bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
+        for face in bm.faces:
+            face.smooth = False
+        me = bpy.data.meshes.new(name)
+        bm.to_mesh(me)
+        me.update()
+        for poly in me.polygons:
+            poly.use_smooth = False
+    finally:
+        bm.free()
+    out = bpy.data.objects.new(name, me)
+    bpy.context.collection.objects.link(out)
+    return out
+
+
+def principled(name, color, metallic, roughness):
+    mat = bpy.data.materials.new(name)
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes["Principled BSDF"]
+    bsdf.inputs["Base Color"].default_value = color
+    bsdf.inputs["Metallic"].default_value = metallic
+    bsdf.inputs["Roughness"].default_value = roughness
+    return mat
+
+
+def assign_slots(obj, wood, metal):
+    mats = obj.data.materials
+    wanted = (wood, metal)
+    for i, mat in enumerate(wanted):
+        if i < len(mats):
+            mats[i] = mat
+        else:
+            mats.append(mat)
+
+
+def world_bbox(obj):
+    corners = [obj.matrix_world @ Vector(c) for c in obj.bound_box]
+    xs = [c.x for c in corners]
+    ys = [c.y for c in corners]
+    zs = [c.z for c in corners]
+    return (min(xs), min(ys), min(zs), max(xs), max(ys), max(zs))
+
+
+def uv_stats(mesh):
+    uv = mesh.uv_layers.active
+    if uv is None:
+        return 0.0, 0.0, 1.0, 1.0, 0, 1.0
+    data = uv.data
+    us = [loop.uv[0] for loop in data]
+    vs = [loop.uv[1] for loop in data]
+    aabbs = []
+    for poly in mesh.polygons:
+        pu = [data[i].uv[0] for i in poly.loop_indices]
+        pv = [data[i].uv[1] for i in poly.loop_indices]
+        aabbs.append((min(pu), min(pv), max(pu), max(pv)))
+    overlap = 0.0
+    for i in range(len(aabbs)):
+        a = aabbs[i]
+        for j in range(i + 1, len(aabbs)):
+            b = aabbs[j]
+            x0 = max(a[0], b[0])
+            y0 = max(a[1], b[1])
+            x1 = min(a[2], b[2])
+            y1 = min(a[3], b[3])
+            overlap += max(0.0, x1 - x0) * max(0.0, y1 - y0)
+    return min(us), min(vs), max(us), max(vs), overlap, len(aabbs)
+
+
+def make_lod(obj, name, ratio, skip_decimate):
+    mesh = obj.data.copy()
+    lod = bpy.data.objects.new(name, mesh)
+    lod.matrix_world = obj.matrix_world.copy()
+    bpy.context.scene.collection.objects.link(lod)
+    if not skip_decimate and 0.0 < ratio < 1.0:
+        mod = lod.modifiers.new("DecimateBudget", "DECIMATE")
+        mod.decimate_type = "COLLAPSE"
+        mod.ratio = ratio
+    return lod
+
+
+def convex_hull_collider(obj, name):
+    mesh = bpy.data.meshes.new(name)
+    bm = bmesh.new()
+    try:
+        bm.from_mesh(obj.data)
+        result = bmesh.ops.convex_hull(bm, input=list(bm.verts))
+        interior = result.get("geom_interior") or []
+        unused = result.get("geom_unused") or []
+        if interior:
+            bmesh.ops.delete(bm, geom=interior, context="VERTS")
+        if unused:
+            bmesh.ops.delete(bm, geom=unused, context="VERTS")
+        bm.to_mesh(mesh)
+        mesh.update()
+    finally:
+        bm.free()
+    collider = bpy.data.objects.new(name, mesh)
+    bpy.context.collection.objects.link(collider)
+    collider.matrix_world = obj.matrix_world.copy()
+    return collider
+
+
+def setup_bake_image(obj, target_mat, size=BAKE_RES):
+    if not obj.data.uv_layers:
+        return None, None
+    img = bpy.data.images.new("BarrowNrm", size, size, alpha=True, float_buffer=False)
+    img.colorspace_settings.name = "Non-Color"
+    nodes = target_mat.node_tree.nodes
+    tex = nodes.new("ShaderNodeTexImage")
+    tex.image = img
+    nodes.active = tex
+    tex.select = True
+    obj.active_material_index = WOOD_IDX
+    return img, tex
+
+
+def bake_normal(high, low):
+    scene = bpy.context.scene
+    scene.render.engine = "CYCLES"
+    scene.cycles.device = "CPU"
+    scene.cycles.samples = 1
+    scene.cycles.use_denoising = False
+    deselect_all()
+    high.select_set(True)
+    low.select_set(True)
+    bpy.context.view_layer.objects.active = low
+    return bpy.ops.object.bake(
+        type="NORMAL",
+        use_selected_to_active=True,
+        cage_extrusion=CAGE_EXTRUSION,
+        use_cage=False,
+        normal_space="TANGENT",
+        margin=4,
+        margin_type="ADJACENT_FACES",
+        use_clear=True,
+        target="IMAGE_TEXTURES",
+    )
+
+
+def export_unity(path, objects):
+    deselect_all()
+    for ob in objects:
+        ob.select_set(True)
+    bpy.context.view_layer.objects.active = objects[0]
+    bpy.ops.export_scene.gltf(
+        filepath=path,
+        use_selection=True,
+        export_yup=True,
+        export_apply=True,
+        export_draco_mesh_compression_enable=False,
+        export_animations=False,
+    )
+
+
+def check(skip_decimate):
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    low = build_barrow_mesh("BarrowLow", bevel_offset=0.005, bevel_segments=2)
+    high = build_barrow_mesh("BarrowHigh", bevel_offset=0.005, bevel_segments=4)
+    wood = principled("BarrowWood", (0.38, 0.21, 0.09, 1.0), 0.0, 0.58)
+    metal = principled("BarrowIron", (0.10, 0.105, 0.12, 1.0), 1.0, 0.30)
+    assign_slots(low, wood, metal)
+    assign_slots(high, wood, metal)
+
+    if low.data is None or len(low.data.polygons) < 6:
+        return fail("barrow mesh did not build", 3), None, None, None, None, None
+
+    base_tris = triangle_count(low.data)
+    mats = [s for s in low.data.materials if s is not None]
+    nmat = len(mats)
+    distinct_mats = len({id(s) for s in mats})
+    idx_counts = {}
+    for poly in low.data.polygons:
+        idx_counts[poly.material_index] = idx_counts.get(poly.material_index, 0) + 1
+    print(f"measured mat_index_counts={idx_counts}")
+    u0, v0, u1, v1, overlap, nfaces = uv_stats(low.data)
+    bb = world_bbox(low)
+    size_x = bb[3] - bb[0]
+    size_y = bb[4] - bb[1]
+    size_z = bb[5] - bb[2]
+
+    img, tex = setup_bake_image(low, wood)
+    if img is None:
+        return fail("barrow has no UV layer", 3), None, None, None, None, None
+    bake_result = bake_normal(high, low)
+
+    lod1 = make_lod(low, "BarrowLOD1", LOD1_TARGET, skip_decimate)
+    lod2 = make_lod(low, "BarrowLOD2", LOD2_TARGET, skip_decimate)
+    bpy.context.view_layer.update()
+    lod1_tris = evaluated_triangle_count(lod1)
+    lod2_tris = evaluated_triangle_count(lod2)
+    r1 = lod1_tris / base_tris if base_tris else 0.0
+    r2 = lod2_tris / base_tris if base_tris else 0.0
+
+    collider_src = build_barrow_mesh("BarrowColSrc", bevel_offset=0.0, bevel_segments=1)
+    collider = convex_hull_collider(collider_src, "BarrowCollider")
+    bpy.data.objects.remove(collider_src, do_unlink=True)
+    col_tris = triangle_count(collider.data)
+
+    export_path = os.path.join(
+        tempfile.gettempdir(),
+        f"bdt_wheelbarrow_{os.getpid()}.glb",
+    )
+    if os.path.exists(export_path):
+        os.remove(export_path)
+    export_unity(export_path, [low, collider])
+    export_size = os.path.getsize(export_path) if os.path.isfile(export_path) else 0
+
+    print(f"blender={tuple(bpy.app.version)} skip_decimate={skip_decimate}")
+    print(
+        f"measured base_tris={base_tris} lod1_tris={lod1_tris} "
+        f"lod2_tris={lod2_tris} r1={r1:.4f} r2={r2:.4f}"
+    )
+    print(
+        f"measured nmat={nmat} uv=({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f}) "
+        f"overlap={overlap:.6f} nfaces={nfaces}"
+    )
+    print(
+        f"measured bbox=({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+        f"outer={OUTER_SIZE} zmin={bb[2]:.4f}"
+    )
+    print(
+        f"measured collider_tris={col_tris} bake={bake_result} "
+        f"bake_has_data={img.has_data} export_bytes={export_size}"
+    )
+
+    if not (BASE_TRIS_MIN <= base_tris <= BASE_TRIS_MAX):
+        return fail(
+            f"base tris {base_tris} not in [{BASE_TRIS_MIN}, {BASE_TRIS_MAX}]",
+            4,
+        ), None, None, None, None, None
+    if nmat != MATERIAL_COUNT or distinct_mats != MATERIAL_COUNT:
+        return fail(
+            f"material slots {nmat} distinct {distinct_mats} != {MATERIAL_COUNT}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(METAL_IDX, 0) < METAL_FACES_MIN:
+        return fail(
+            f"metal faces {idx_counts.get(METAL_IDX, 0)} < {METAL_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(WOOD_IDX, 0) < WOOD_FACES_MIN:
+        return fail(
+            f"wood faces {idx_counts.get(WOOD_IDX, 0)} < {WOOD_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if u0 < -UV_EPS or v0 < -UV_EPS or u1 > 1.0 + UV_EPS or v1 > 1.0 + UV_EPS:
+        return fail(
+            f"UVs outside 0..1: ({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f})",
+            6,
+        ), None, None, None, None, None
+    if overlap > UV_OVERLAP_MAX:
+        return fail(
+            f"UV AABB overlap {overlap:.6f} > {UV_OVERLAP_MAX}",
+            7,
+        ), None, None, None, None, None
+    if (
+        abs(size_x - OUTER_SIZE[0]) > BBOX_TOL
+        or abs(size_y - OUTER_SIZE[1]) > BBOX_TOL
+        or abs(size_z - OUTER_SIZE[2]) > BBOX_TOL
+    ):
+        return fail(
+            f"bbox ({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+            f"off outer {OUTER_SIZE}",
+            8,
+        ), None, None, None, None, None
+    if not (LOD1_RATIO_MIN <= r1 <= LOD1_RATIO_MAX):
+        return fail(
+            f"LOD1 ratio {r1:.4f} not in [{LOD1_RATIO_MIN}, {LOD1_RATIO_MAX}] "
+            "(--skip-decimate is the designed fail)",
+            9,
+        ), None, None, None, None, None
+    if not (LOD2_RATIO_MIN <= r2 <= LOD2_RATIO_MAX):
+        return fail(
+            f"LOD2 ratio {r2:.4f} not in [{LOD2_RATIO_MIN}, {LOD2_RATIO_MAX}]",
+            9,
+        ), None, None, None, None, None
+    if col_tris > COLLIDER_TRIS_MAX:
+        return fail(
+            f"collider tris {col_tris} > {COLLIDER_TRIS_MAX}",
+            11,
+        ), None, None, None, None, None
+    if bake_result != {"FINISHED"} or not img.has_data:
+        return fail(
+            f"bake failed result={bake_result} has_data={img.has_data}",
+            12,
+        ), None, None, None, None, None
+    if export_size <= 0:
+        return fail("export file missing or empty", 13), None, None, None, None, None
+    return 0, low, high, wood, tex, collider
+
+
+def wire_normal(mat, tex):
+    nt = mat.node_tree
+    bsdf = nt.nodes["Principled BSDF"]
+    nrm = nt.nodes.new("ShaderNodeNormalMap")
+    nrm.inputs["Strength"].default_value = 1.0
+    nt.links.new(tex.outputs["Color"], nrm.inputs["Color"])
+    nt.links.new(nrm.outputs["Normal"], bsdf.inputs["Normal"])
+
+
+def render_still(low, wood, tex, path, engine):
+    scene = bpy.context.scene
+    wire_normal(wood, tex)
+    for ob in list(scene.objects):
+        if ob.type == "MESH" and ob != low:
+            ob.hide_render = True
+            ob.hide_viewport = True
+
+    low.rotation_euler.z = math.radians(-32.0)
+    low.rotation_euler.x = math.radians(0.0)
+
+    floor_me = bpy.data.meshes.new("Floor")
+    bm = bmesh.new()
+    try:
+        bmesh.ops.create_grid(bm, x_segments=1, y_segments=1, size=14.0)
+        bm.to_mesh(floor_me)
+    finally:
+        bm.free()
+    fmat = bpy.data.materials.new("Floor")
+    fmat.use_nodes = True
+    fb = fmat.node_tree.nodes["Principled BSDF"]
+    fb.inputs["Base Color"].default_value = (0.03, 0.032, 0.037, 1.0)
+    fb.inputs["Roughness"].default_value = 0.7
+    floor_me.materials.append(fmat)
+    floor = bpy.data.objects.new("Floor", floor_me)
+    scene.collection.objects.link(floor)
+    wall = bpy.data.objects.new("Wall", floor_me.copy())
+    wall.location = (0.0, 8.5, 0.0)
+    wall.rotation_euler = (math.radians(90), 0.0, 0.0)
+    scene.collection.objects.link(wall)
+
+    world = bpy.data.worlds.new("World")
+    world.use_nodes = True
+    world.node_tree.nodes["Background"].inputs["Color"].default_value = (
+        0.02, 0.021, 0.025, 1.0,
+    )
+    scene.world = world
+
+    def light(name, loc, energy, size, col, rot):
+        ld = bpy.data.lights.new(name, "AREA")
+        ld.energy = energy
+        ld.size = size
+        ld.color = col
+        ob = bpy.data.objects.new(name, ld)
+        ob.location = loc
+        ob.rotation_euler = tuple(math.radians(a) for a in rot)
+        scene.collection.objects.link(ob)
+
+    light("Key", (-3.6, -5.0, 5.4), 660.0, 4.0, (1.0, 0.94, 0.86), (50, 0, -36))
+    light("Fill", (5.0, -3.4, 2.4), 46.0, 8.0, (0.72, 0.82, 1.0), (62, 0, 50))
+    light("Wedge", (2.2, 4.0, 3.8), 600.0, 5.5, (1.0, 0.70, 0.40), (-70, 0, 198))
+
+    cam_data = bpy.data.cameras.new("Cam")
+    cam_data.lens = 50.0
+    cam = bpy.data.objects.new("Cam", cam_data)
+    cam.location = (1.82, -2.22, 1.12)
+    scene.collection.objects.link(cam)
+    aim = bpy.data.objects.new("Aim", None)
+    aim.location = (0.0, 0.0, 0.34)
+    scene.collection.objects.link(aim)
+    con = cam.constraints.new("TRACK_TO")
+    con.target = aim
+    con.track_axis = "TRACK_NEGATIVE_Z"
+    con.up_axis = "UP_Y"
+    scene.camera = cam
+
+    scene.render.engine = "CYCLES" if engine == "cycles" else eevee_engine_id()
+    if engine == "cycles":
+        scene.cycles.samples = 32
+        scene.cycles.device = "CPU"
+    else:
+        try:
+            scene.eevee.taa_render_samples = 64
+        except AttributeError:
+            pass
+    scene.render.resolution_x = 1280
+    scene.render.resolution_y = 720
+    scene.render.image_settings.file_format = (
+        "WEBP" if path.lower().endswith(".webp") else "PNG"
+    )
+    if path.lower().endswith(".webp"):
+        scene.render.image_settings.quality = 90
+    scene.render.filepath = path
+    scene.view_settings.view_transform = "Standard"
+
+    fcode = gallery_framing.check_framing(
+        scene, cam, hero=[low], elements=[low], stage=[floor, wall],
+    )
+    if fcode:
+        return fcode
+    bpy.ops.render.render(write_still=True)
+    if not (os.path.exists(path) and os.path.getsize(path) > 0):
+        return fail("render produced no file", 14)
+    return 0
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    p = argparse.ArgumentParser()
+    p.add_argument("--output", default=None)
+    p.add_argument("--engine", default="eevee", choices=("eevee", "cycles"))
+    p.add_argument(
+        "--skip-decimate",
+        action="store_true",
+        help="falsification: skip the LOD DECIMATE stage",
+    )
+    args = p.parse_args(argv)
+
+    code, low, _high, wood, tex, _col = check(args.skip_decimate)
+    if code:
+        return code
+    if args.output:
+        rcode = render_still(low, wood, tex, os.path.abspath(args.output), args.engine)
+        if rcode:
+            return rcode
+        print(f"rendered still {args.output}")
+    print("wheelbarrow OK")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except Exception as e:
+        traceback.print_exc()
+        print(f"FATAL: {e}", file=sys.stderr)
+        sys.exit(1)
+

+    

+  

+  
+  

+    

+      generated from examples/gallery.json
+      CC-BY-NC-ND-4.0
+      exit 0
+    

+  

+  
+
+
diff --git a/showcase/gallery.json b/showcase/gallery.json
index 89c2705..b585356 100644
--- a/showcase/gallery.json
+++ b/showcase/gallery.json
@@ -136,6 +136,30 @@
         "mesh",
         "export"
       ]
+    },
+    {
+      "name": "park-bench",
+      "dir": "showcase/park-bench",
+      "teaches": "A procedural wrought-iron park bench through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.",
+      "witnessesFix": "Recomputed: 2100 tris, two materials with 510 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.080×0.566×0.853 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.",
+      "hero": "docs/gallery/assets/park-bench-hero.webp",
+      "preview": "showcase/park-bench/preview.webp",
+      "tags": [
+        "mesh",
+        "export"
+      ]
+    },
+    {
+      "name": "wheelbarrow",
+      "dir": "showcase/wheelbarrow",
+      "teaches": "A procedural wooden wheelbarrow through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.",
+      "witnessesFix": "Recomputed: 3088 tris, two materials with 308 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.418×0.463×0.594 m, LOD ratios in band (5.2 COLLAPSE more aggressive on LOD2), convex collider 106 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.",
+      "hero": "docs/gallery/assets/wheelbarrow-hero.webp",
+      "preview": "showcase/wheelbarrow/preview.webp",
+      "tags": [
+        "mesh",
+        "export"
+      ]
     }
   ]
 }
diff --git a/showcase/park-bench/README.md b/showcase/park-bench/README.md
new file mode 100644
index 0000000..8760682
--- /dev/null
+++ b/showcase/park-bench/README.md
@@ -0,0 +1,74 @@
+# Park bench
+
+A showcase piece, not an example. Procedural wrought-iron park bench
+(scrolled legs, slatted seat and back, armrests) then the shipped
+pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain,
+convex collider, Unity glTF export.
+
+It asserts **budget conformance** of the generated result. It does not
+witness an API contract. "It rendered without error" is not a check.
+
+**Composes** skills `mesh-editing-and-bmesh`, `bake-high-to-low`,
+`depsgraph-and-evaluated-data`, `engine-export-presets`, and snippets
+`bake_normal_high_to_low.py`, `setup_bake_target_image.py`,
+`lod_chain.py` / `decimate_to_budget.py`, `convex_hull_collider.py`,
+`export_preset_unity.py` (helpers copied, not imported as a package).
+
+## Budgets
+
+Declared as named constants; every gate **recomputes** from the mesh,
+materials, UVs, evaluated LOD, collider, or export file.
+
+| Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) |
+| --- | --- | --- |
+| Base triangles | 2000–2200 | 2100 / 2100 / 2100 |
+| LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.4952 |
+| LOD2 ratio | 0.10–0.35 of base | 0.2200 / 0.2200 / 0.1400 |
+| Materials | exactly 2 distinct, ≥48 metal faces | 2 slots, 510 metal |
+| UVs | in `0..1`, AABB overlap ≤ 1e-5 | in range, overlap 0 |
+| Outer AABB | (1.080, 0.566, 0.853) m ± 0.01 | (1.0800, 0.5657, 0.8531), zmin 0 |
+| Collider tris | ≤ 140 | 106 |
+| Export | written, size > 0 | 159868 / 159868 / 159852 bytes |
+
+DECIMATE COLLAPSE triangle counts are **not** identical across series —
+5.2.1 is more aggressive on LOD2. The gate is a ratio band, not an
+exact count. Bake pixels are stochastic; the gate is `has_data` plus
+operator `FINISHED`, not byte-identity. Construction uses no RNG.
+Export byte counts differ by 16 B on 5.2.1 (glTF serializer), not a
+gated axis.
+
+`--skip-decimate` skips the LOD DECIMATE stage so LOD1 ratio is 1.0 and
+exit 9 fires. That is the named budget the falsifier violates.
+
+## Run
+
+```bash
+blender --background --python park_bench.py --
+blender --background --python park_bench.py -- --skip-decimate
+blender --background --python park_bench.py -- --output bench.png
+```
+
+Smoke does not pass `--output` or `--skip-decimate`.
+
+## Exit codes
+
+File-local. `9` is a valid check code. `10` is reserved for
+`gallery_framing.check_framing` on the `--output` path.
+
+| Code | Meaning |
+| --- | --- |
+| 0 | Success |
+| 1 | Uncaught exception (FATAL wrapper) |
+| 2 | argparse / usage |
+| 3 | Mesh did not build / no UV layer |
+| 4 | Base triangle count outside range |
+| 5 | Material count ≠ 2 distinct slots, or wood/metal faces missing |
+| 6 | UVs outside 0..1 |
+| 7 | UV AABB overlap above tolerance |
+| 8 | World AABB off declared outer size |
+| 9 | LOD ratio band (`--skip-decimate` lands here) |
+| 10 | Framing gate (render path only) |
+| 11 | Collider triangle count above ceiling |
+| 12 | Bake did not finish or image has no data |
+| 13 | Export file missing or empty |
+| 14 | `--output` produced no file |
diff --git a/showcase/park-bench/park_bench.py b/showcase/park-bench/park_bench.py
new file mode 100644
index 0000000..d74d12b
--- /dev/null
+++ b/showcase/park-bench/park_bench.py
@@ -0,0 +1,756 @@
+"""Game-ready park bench — a showcase piece, not an example.
+
+Asserts budget conformance of a procedural wrought-iron bench (scrolled
+legs, slatted seat and back) after composing shipped pipeline pieces:
+bmesh construction, UVs, two materials, high-to-low normal bake, LOD
+chain, convex collider, Unity glTF export.
+
+Budgets are declared below and recomputed from the generated result.
+They are not API-contract witnesses. ``--skip-decimate`` skips the LOD
+DECIMATE stage so the LOD-ratio budget fails.
+
+No RNG. Construction is closed-form. DECIMATE COLLAPSE triangle counts
+are not byte-identical across Blender versions — the LOD gate is a
+ratio band, not an exact count.
+
+    blender --background --python park_bench.py --
+    blender --background --python park_bench.py -- --skip-decimate
+    blender --background --python park_bench.py -- --output bench.png
+"""
+import argparse
+import math
+import os
+import sys
+import tempfile
+import traceback
+
+import bmesh
+import bpy
+from mathutils import Euler, Vector
+
+_REPO = os.path.abspath(
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir, os.pardir)
+)
+sys.path.insert(0, os.path.join(_REPO, "examples"))
+sys.dont_write_bytecode = True
+import gallery_framing  # noqa: E402
+
+SEAT_W = 1.18
+SEAT_D = 0.46
+SEAT_Z = 0.44
+N_SEAT = 6
+N_BACK = 4
+SLAT_T = 0.032
+BACK_H = 0.40
+IRON_T = 0.026
+SCROLL_R = 0.10
+SCROLL_N = 12
+ARM_Z = 0.62
+
+BBOX_TOL = 0.01
+OUTER_SIZE = (1.080, 0.566, 0.853)
+BASE_TRIS_MIN = 2000
+BASE_TRIS_MAX = 2200
+LOD1_RATIO_MIN = 0.32
+LOD1_RATIO_MAX = 0.62
+LOD2_RATIO_MIN = 0.10
+LOD2_RATIO_MAX = 0.35
+LOD1_TARGET = 0.50
+LOD2_TARGET = 0.22
+MATERIAL_COUNT = 2
+UV_EPS = 1e-4
+UV_OVERLAP_MAX = 1e-5
+COLLIDER_TRIS_MAX = 140
+BAKE_RES = 256
+CAGE_EXTRUSION = 0.08
+METAL_FACES_MIN = 48
+WOOD_FACES_MIN = 24
+
+WOOD_IDX = 0
+METAL_IDX = 1
+
+
+def eevee_engine_id():
+    return "BLENDER_EEVEE" if bpy.app.version >= (5, 0, 0) else "BLENDER_EEVEE_NEXT"
+
+
+def fail(msg, code):
+    print(f"ERROR: {msg}", file=sys.stderr)
+    return code
+
+
+def triangle_count(mesh):
+    mesh.calc_loop_triangles()
+    return len(mesh.loop_triangles)
+
+
+def evaluated_triangle_count(obj):
+    depsgraph = bpy.context.evaluated_depsgraph_get()
+    eval_obj = obj.evaluated_get(depsgraph)
+    eval_mesh = eval_obj.to_mesh()
+    try:
+        eval_mesh.calc_loop_triangles()
+        return len(eval_mesh.loop_triangles)
+    finally:
+        eval_obj.to_mesh_clear()
+
+
+def deselect_all():
+    for ob in list(bpy.context.view_layer.objects):
+        if ob is None:
+            continue
+        ob.select_set(False)
+
+
+def add_box(bm, loc, scale, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cube(bm, size=1.0)
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        p = Vector((v.co.x * scale[0], v.co.y * scale[1], v.co.z * scale[2]))
+        v.co = rot @ p + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_oriented_box(bm, a, b, scale_xy, mat_idx):
+    a = Vector(a)
+    b = Vector(b)
+    delta = b - a
+    length = delta.length
+    if length < 1e-8:
+        return []
+    quat = Vector((0.0, 0.0, 1.0)).rotation_difference(delta.normalized())
+    eul = quat.to_euler("XYZ")
+    return add_box(
+        bm,
+        ((a + b) * 0.5),
+        (scale_xy[0], scale_xy[1], length),
+        mat_idx,
+        euler=(eul.x, eul.y, eul.z),
+    )
+
+
+def add_arc_yz(bm, x, cy, cz, radius, a0, a1, n, thick, mat_idx):
+    pts = []
+    for i in range(n + 1):
+        t = i / n
+        ang = a0 + (a1 - a0) * t
+        pts.append((x, cy + radius * math.cos(ang), cz + radius * math.sin(ang)))
+    verts = []
+    for p0, p1 in zip(pts, pts[1:]):
+        verts.extend(add_oriented_box(bm, p0, p1, (thick, thick), mat_idx))
+    return verts
+
+
+def pack_uvs(bm, margin=0.08):
+    uv = bm.loops.layers.uv.new("UVMap")
+    faces = list(bm.faces)
+    n = len(faces)
+    cols = max(1, math.ceil(math.sqrt(n)))
+    rows = max(1, math.ceil(n / cols))
+    cell_w = 1.0 / cols
+    cell_h = 1.0 / rows
+    pad_u = margin * cell_w * 0.5
+    pad_v = margin * cell_h * 0.5
+    usable_w = cell_w - 2.0 * pad_u
+    usable_h = cell_h - 2.0 * pad_v
+    for i, face in enumerate(faces):
+        col = i % cols
+        row = i // cols
+        nrm = face.normal
+        ax = abs(nrm.x)
+        ay = abs(nrm.y)
+        az = abs(nrm.z)
+        coords = []
+        for loop in face.loops:
+            co = loop.vert.co
+            if az >= ax and az >= ay:
+                coords.append((co.x, co.y))
+            elif ax >= ay:
+                coords.append((co.y, co.z))
+            else:
+                coords.append((co.x, co.z))
+        xs = [c[0] for c in coords]
+        ys = [c[1] for c in coords]
+        minx, maxx = min(xs), max(xs)
+        miny, maxy = min(ys), max(ys)
+        dx = max(maxx - minx, 1e-8)
+        dy = max(maxy - miny, 1e-8)
+        origin_u = col * cell_w + pad_u
+        origin_v = row * cell_h + pad_v
+        for loop, (x, y) in zip(face.loops, coords):
+            loop[uv].uv = (
+                origin_u + (x - minx) / dx * usable_w,
+                origin_v + (y - miny) / dy * usable_h,
+            )
+
+
+def build_bench_mesh(name, bevel_offset, bevel_segments):
+    bm = bmesh.new()
+    try:
+        wood = []
+        hx = SEAT_W / 2.0 - 0.08
+        hy = SEAT_D / 2.0 - 0.05
+        # Span past the post centers (±hx) so slats insert into the iron frame.
+        slat_span = 2.0 * hx + IRON_T
+        usable = SEAT_D - 0.08
+        slat_w = usable / N_SEAT
+        y0 = -hy + slat_w / 2.0 + 0.01
+        for i in range(N_SEAT):
+            y = y0 + i * slat_w
+            wood.extend(
+                add_box(
+                    bm,
+                    (0.0, y, SEAT_Z + SLAT_T / 2.0),
+                    (slat_span, slat_w * 0.78, SLAT_T),
+                    WOOD_IDX,
+                )
+            )
+        for i in range(N_BACK):
+            z = SEAT_Z + SLAT_T + 0.05 + i * (BACK_H / N_BACK)
+            wood.extend(
+                add_box(
+                    bm,
+                    (0.0, hy, z),
+                    (slat_span, SLAT_T, slat_w * 0.72),
+                    WOOD_IDX,
+                )
+            )
+
+        if bevel_offset > 0.0:
+            edges = list({e for v in wood for e in v.link_edges})
+            ret = bmesh.ops.bevel(
+                bm,
+                geom=edges,
+                offset=bevel_offset,
+                segments=bevel_segments,
+                profile=0.5,
+                affect="EDGES",
+                clamp_overlap=True,
+            )
+            for f in ret.get("faces") or []:
+                f.material_index = WOOD_IDX
+
+        t = IRON_T
+        add_box(bm, (0.0, -hy, SEAT_Z - 0.018), (SEAT_W - 0.10, t * 1.15, t), METAL_IDX)
+        add_box(bm, (0.0, hy, SEAT_Z - 0.018), (SEAT_W - 0.10, t * 1.15, t), METAL_IDX)
+        for xsign in (-1.0, 1.0):
+            add_box(
+                bm,
+                (xsign * hx, 0.0, SEAT_Z - 0.018),
+                (t * 1.15, SEAT_D - 0.08, t),
+                METAL_IDX,
+            )
+
+        back_top = SEAT_Z + SLAT_T + BACK_H + 0.02
+        for xsign in (-1.0, 1.0):
+            x = xsign * hx
+            add_oriented_box(
+                bm, (x, hy, SEAT_Z), (x, hy, back_top), (t, t), METAL_IDX
+            )
+            add_oriented_box(
+                bm, (x, -hy, SEAT_Z), (x, -hy, ARM_Z), (t, t), METAL_IDX
+            )
+            add_oriented_box(
+                bm, (x, -hy, ARM_Z), (x, hy, ARM_Z), (t * 0.9, t * 0.9), METAL_IDX
+            )
+            add_oriented_box(
+                bm,
+                (x, -hy, SCROLL_R + 0.02),
+                (x, -hy, SEAT_Z),
+                (t, t),
+                METAL_IDX,
+            )
+            add_oriented_box(
+                bm,
+                (x, hy, SCROLL_R + 0.02),
+                (x, hy, SEAT_Z),
+                (t, t),
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                -hy + 0.01,
+                SCROLL_R,
+                SCROLL_R,
+                math.pi / 2.0,
+                math.pi + 0.45,
+                SCROLL_N,
+                t,
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                hy - 0.01,
+                SCROLL_R,
+                SCROLL_R,
+                math.pi / 2.0,
+                -0.45,
+                SCROLL_N,
+                t,
+                METAL_IDX,
+            )
+            add_arc_yz(
+                bm,
+                x,
+                -hy - 0.02,
+                ARM_Z - 0.04,
+                0.07,
+                math.pi * 0.15,
+                math.pi * 0.95,
+                10,
+                t * 0.85,
+                METAL_IDX,
+            )
+
+        add_box(bm, (0.0, hy, back_top), (SEAT_W - 0.12, t, t), METAL_IDX)
+        add_box(bm, (0.0, 0.0, 0.18), (SEAT_W - 0.22, t * 0.9, t * 0.9), METAL_IDX)
+        add_box(bm, (0.0, 0.0, 0.18), (t * 0.9, SEAT_D - 0.14, t * 0.9), METAL_IDX)
+
+        xs = [v.co.x for v in bm.verts]
+        ys = [v.co.y for v in bm.verts]
+        zs = [v.co.z for v in bm.verts]
+        cx = 0.5 * (min(xs) + max(xs))
+        cy = 0.5 * (min(ys) + max(ys))
+        zmin = min(zs)
+        for v in bm.verts:
+            v.co.x -= cx
+            v.co.y -= cy
+            v.co.z -= zmin
+            if v.co.z < 0.0:
+                v.co.z = 0.0
+
+        pack_uvs(bm)
+        bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
+        for face in bm.faces:
+            face.smooth = False
+        me = bpy.data.meshes.new(name)
+        bm.to_mesh(me)
+        me.update()
+        for poly in me.polygons:
+            poly.use_smooth = False
+    finally:
+        bm.free()
+    out = bpy.data.objects.new(name, me)
+    bpy.context.collection.objects.link(out)
+    return out
+
+
+def principled(name, color, metallic, roughness):
+    mat = bpy.data.materials.new(name)
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes["Principled BSDF"]
+    bsdf.inputs["Base Color"].default_value = color
+    bsdf.inputs["Metallic"].default_value = metallic
+    bsdf.inputs["Roughness"].default_value = roughness
+    return mat
+
+
+def assign_slots(obj, wood, metal):
+    mats = obj.data.materials
+    wanted = (wood, metal)
+    for i, mat in enumerate(wanted):
+        if i < len(mats):
+            mats[i] = mat
+        else:
+            mats.append(mat)
+
+
+def world_bbox(obj):
+    corners = [obj.matrix_world @ Vector(c) for c in obj.bound_box]
+    xs = [c.x for c in corners]
+    ys = [c.y for c in corners]
+    zs = [c.z for c in corners]
+    return (min(xs), min(ys), min(zs), max(xs), max(ys), max(zs))
+
+
+def uv_stats(mesh):
+    uv = mesh.uv_layers.active
+    if uv is None:
+        return 0.0, 0.0, 1.0, 1.0, 0, 1.0
+    data = uv.data
+    us = [loop.uv[0] for loop in data]
+    vs = [loop.uv[1] for loop in data]
+    aabbs = []
+    for poly in mesh.polygons:
+        pu = [data[i].uv[0] for i in poly.loop_indices]
+        pv = [data[i].uv[1] for i in poly.loop_indices]
+        aabbs.append((min(pu), min(pv), max(pu), max(pv)))
+    overlap = 0.0
+    for i in range(len(aabbs)):
+        a = aabbs[i]
+        for j in range(i + 1, len(aabbs)):
+            b = aabbs[j]
+            x0 = max(a[0], b[0])
+            y0 = max(a[1], b[1])
+            x1 = min(a[2], b[2])
+            y1 = min(a[3], b[3])
+            overlap += max(0.0, x1 - x0) * max(0.0, y1 - y0)
+    return min(us), min(vs), max(us), max(vs), overlap, len(aabbs)
+
+
+def make_lod(obj, name, ratio, skip_decimate):
+    mesh = obj.data.copy()
+    lod = bpy.data.objects.new(name, mesh)
+    lod.matrix_world = obj.matrix_world.copy()
+    bpy.context.scene.collection.objects.link(lod)
+    if not skip_decimate and 0.0 < ratio < 1.0:
+        mod = lod.modifiers.new("DecimateBudget", "DECIMATE")
+        mod.decimate_type = "COLLAPSE"
+        mod.ratio = ratio
+    return lod
+
+
+def convex_hull_collider(obj, name):
+    mesh = bpy.data.meshes.new(name)
+    bm = bmesh.new()
+    try:
+        bm.from_mesh(obj.data)
+        result = bmesh.ops.convex_hull(bm, input=list(bm.verts))
+        interior = result.get("geom_interior") or []
+        unused = result.get("geom_unused") or []
+        if interior:
+            bmesh.ops.delete(bm, geom=interior, context="VERTS")
+        if unused:
+            bmesh.ops.delete(bm, geom=unused, context="VERTS")
+        bm.to_mesh(mesh)
+        mesh.update()
+    finally:
+        bm.free()
+    collider = bpy.data.objects.new(name, mesh)
+    bpy.context.collection.objects.link(collider)
+    collider.matrix_world = obj.matrix_world.copy()
+    return collider
+
+
+def setup_bake_image(obj, target_mat, size=BAKE_RES):
+    if not obj.data.uv_layers:
+        return None, None
+    img = bpy.data.images.new("BenchNrm", size, size, alpha=True, float_buffer=False)
+    img.colorspace_settings.name = "Non-Color"
+    nodes = target_mat.node_tree.nodes
+    tex = nodes.new("ShaderNodeTexImage")
+    tex.image = img
+    nodes.active = tex
+    tex.select = True
+    obj.active_material_index = WOOD_IDX
+    return img, tex
+
+
+def bake_normal(high, low):
+    scene = bpy.context.scene
+    scene.render.engine = "CYCLES"
+    scene.cycles.device = "CPU"
+    scene.cycles.samples = 1
+    scene.cycles.use_denoising = False
+    deselect_all()
+    high.select_set(True)
+    low.select_set(True)
+    bpy.context.view_layer.objects.active = low
+    return bpy.ops.object.bake(
+        type="NORMAL",
+        use_selected_to_active=True,
+        cage_extrusion=CAGE_EXTRUSION,
+        use_cage=False,
+        normal_space="TANGENT",
+        margin=4,
+        margin_type="ADJACENT_FACES",
+        use_clear=True,
+        target="IMAGE_TEXTURES",
+    )
+
+
+def export_unity(path, objects):
+    deselect_all()
+    for ob in objects:
+        ob.select_set(True)
+    bpy.context.view_layer.objects.active = objects[0]
+    bpy.ops.export_scene.gltf(
+        filepath=path,
+        use_selection=True,
+        export_yup=True,
+        export_apply=True,
+        export_draco_mesh_compression_enable=False,
+        export_animations=False,
+    )
+
+
+def check(skip_decimate):
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    low = build_bench_mesh("BenchLow", bevel_offset=0.005, bevel_segments=2)
+    high = build_bench_mesh("BenchHigh", bevel_offset=0.005, bevel_segments=4)
+    wood = principled("BenchWood", (0.40, 0.20, 0.07, 1.0), 0.0, 0.58)
+    metal = principled("BenchIron", (0.09, 0.095, 0.11, 1.0), 1.0, 0.28)
+    assign_slots(low, wood, metal)
+    assign_slots(high, wood, metal)
+
+    if low.data is None or len(low.data.polygons) < 6:
+        return fail("bench mesh did not build", 3), None, None, None, None, None
+
+    base_tris = triangle_count(low.data)
+    mats = [s for s in low.data.materials if s is not None]
+    nmat = len(mats)
+    distinct_mats = len({id(s) for s in mats})
+    idx_counts = {}
+    for poly in low.data.polygons:
+        idx_counts[poly.material_index] = idx_counts.get(poly.material_index, 0) + 1
+    print(f"measured mat_index_counts={idx_counts}")
+    u0, v0, u1, v1, overlap, nfaces = uv_stats(low.data)
+    bb = world_bbox(low)
+    size_x = bb[3] - bb[0]
+    size_y = bb[4] - bb[1]
+    size_z = bb[5] - bb[2]
+
+    img, tex = setup_bake_image(low, wood)
+    if img is None:
+        return fail("bench has no UV layer", 3), None, None, None, None, None
+    bake_result = bake_normal(high, low)
+
+    lod1 = make_lod(low, "BenchLOD1", LOD1_TARGET, skip_decimate)
+    lod2 = make_lod(low, "BenchLOD2", LOD2_TARGET, skip_decimate)
+    bpy.context.view_layer.update()
+    lod1_tris = evaluated_triangle_count(lod1)
+    lod2_tris = evaluated_triangle_count(lod2)
+    r1 = lod1_tris / base_tris if base_tris else 0.0
+    r2 = lod2_tris / base_tris if base_tris else 0.0
+
+    collider_src = build_bench_mesh("BenchColSrc", bevel_offset=0.0, bevel_segments=1)
+    collider = convex_hull_collider(collider_src, "BenchCollider")
+    bpy.data.objects.remove(collider_src, do_unlink=True)
+    col_tris = triangle_count(collider.data)
+
+    export_path = os.path.join(
+        tempfile.gettempdir(),
+        f"bdt_park_bench_{os.getpid()}.glb",
+    )
+    if os.path.exists(export_path):
+        os.remove(export_path)
+    export_unity(export_path, [low, collider])
+    export_size = os.path.getsize(export_path) if os.path.isfile(export_path) else 0
+
+    print(f"blender={tuple(bpy.app.version)} skip_decimate={skip_decimate}")
+    print(
+        f"measured base_tris={base_tris} lod1_tris={lod1_tris} "
+        f"lod2_tris={lod2_tris} r1={r1:.4f} r2={r2:.4f}"
+    )
+    print(
+        f"measured nmat={nmat} uv=({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f}) "
+        f"overlap={overlap:.6f} nfaces={nfaces}"
+    )
+    print(
+        f"measured bbox=({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+        f"outer={OUTER_SIZE} zmin={bb[2]:.4f}"
+    )
+    print(
+        f"measured collider_tris={col_tris} bake={bake_result} "
+        f"bake_has_data={img.has_data} export_bytes={export_size}"
+    )
+
+    if not (BASE_TRIS_MIN <= base_tris <= BASE_TRIS_MAX):
+        return fail(
+            f"base tris {base_tris} not in [{BASE_TRIS_MIN}, {BASE_TRIS_MAX}]",
+            4,
+        ), None, None, None, None, None
+    if nmat != MATERIAL_COUNT or distinct_mats != MATERIAL_COUNT:
+        return fail(
+            f"material slots {nmat} distinct {distinct_mats} != {MATERIAL_COUNT}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(METAL_IDX, 0) < METAL_FACES_MIN:
+        return fail(
+            f"metal faces {idx_counts.get(METAL_IDX, 0)} < {METAL_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(WOOD_IDX, 0) < WOOD_FACES_MIN:
+        return fail(
+            f"wood faces {idx_counts.get(WOOD_IDX, 0)} < {WOOD_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if u0 < -UV_EPS or v0 < -UV_EPS or u1 > 1.0 + UV_EPS or v1 > 1.0 + UV_EPS:
+        return fail(
+            f"UVs outside 0..1: ({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f})",
+            6,
+        ), None, None, None, None, None
+    if overlap > UV_OVERLAP_MAX:
+        return fail(
+            f"UV AABB overlap {overlap:.6f} > {UV_OVERLAP_MAX}",
+            7,
+        ), None, None, None, None, None
+    if (
+        abs(size_x - OUTER_SIZE[0]) > BBOX_TOL
+        or abs(size_y - OUTER_SIZE[1]) > BBOX_TOL
+        or abs(size_z - OUTER_SIZE[2]) > BBOX_TOL
+    ):
+        return fail(
+            f"bbox ({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+            f"off outer {OUTER_SIZE}",
+            8,
+        ), None, None, None, None, None
+    if not (LOD1_RATIO_MIN <= r1 <= LOD1_RATIO_MAX):
+        return fail(
+            f"LOD1 ratio {r1:.4f} not in [{LOD1_RATIO_MIN}, {LOD1_RATIO_MAX}] "
+            "(--skip-decimate is the designed fail)",
+            9,
+        ), None, None, None, None, None
+    if not (LOD2_RATIO_MIN <= r2 <= LOD2_RATIO_MAX):
+        return fail(
+            f"LOD2 ratio {r2:.4f} not in [{LOD2_RATIO_MIN}, {LOD2_RATIO_MAX}]",
+            9,
+        ), None, None, None, None, None
+    if col_tris > COLLIDER_TRIS_MAX:
+        return fail(
+            f"collider tris {col_tris} > {COLLIDER_TRIS_MAX}",
+            11,
+        ), None, None, None, None, None
+    if bake_result != {"FINISHED"} or not img.has_data:
+        return fail(
+            f"bake failed result={bake_result} has_data={img.has_data}",
+            12,
+        ), None, None, None, None, None
+    if export_size <= 0:
+        return fail("export file missing or empty", 13), None, None, None, None, None
+    return 0, low, high, wood, tex, collider
+
+
+def wire_normal(mat, tex):
+    nt = mat.node_tree
+    bsdf = nt.nodes["Principled BSDF"]
+    nrm = nt.nodes.new("ShaderNodeNormalMap")
+    nrm.inputs["Strength"].default_value = 1.0
+    nt.links.new(tex.outputs["Color"], nrm.inputs["Color"])
+    nt.links.new(nrm.outputs["Normal"], bsdf.inputs["Normal"])
+
+
+def render_still(low, wood, tex, path, engine):
+    scene = bpy.context.scene
+    wire_normal(wood, tex)
+    for ob in list(scene.objects):
+        if ob.type == "MESH" and ob != low:
+            ob.hide_render = True
+            ob.hide_viewport = True
+
+    low.rotation_euler.z = math.radians(-14.0)
+    low.rotation_euler.x = math.radians(2.0)
+
+    floor_me = bpy.data.meshes.new("Floor")
+    bm = bmesh.new()
+    try:
+        bmesh.ops.create_grid(bm, x_segments=1, y_segments=1, size=14.0)
+        bm.to_mesh(floor_me)
+    finally:
+        bm.free()
+    fmat = bpy.data.materials.new("Floor")
+    fmat.use_nodes = True
+    fb = fmat.node_tree.nodes["Principled BSDF"]
+    fb.inputs["Base Color"].default_value = (0.03, 0.032, 0.037, 1.0)
+    fb.inputs["Roughness"].default_value = 0.7
+    floor_me.materials.append(fmat)
+    floor = bpy.data.objects.new("Floor", floor_me)
+    scene.collection.objects.link(floor)
+    wall = bpy.data.objects.new("Wall", floor_me.copy())
+    wall.location = (0.0, 8.5, 0.0)
+    wall.rotation_euler = (math.radians(90), 0.0, 0.0)
+    scene.collection.objects.link(wall)
+
+    world = bpy.data.worlds.new("World")
+    world.use_nodes = True
+    world.node_tree.nodes["Background"].inputs["Color"].default_value = (
+        0.02, 0.021, 0.025, 1.0,
+    )
+    scene.world = world
+
+    def light(name, loc, energy, size, col, rot):
+        ld = bpy.data.lights.new(name, "AREA")
+        ld.energy = energy
+        ld.size = size
+        ld.color = col
+        ob = bpy.data.objects.new(name, ld)
+        ob.location = loc
+        ob.rotation_euler = tuple(math.radians(a) for a in rot)
+        scene.collection.objects.link(ob)
+
+    light("Key", (-3.6, -5.0, 5.4), 660.0, 4.0, (1.0, 0.94, 0.86), (50, 0, -36))
+    light("Fill", (5.0, -3.4, 2.4), 46.0, 8.0, (0.72, 0.82, 1.0), (62, 0, 50))
+    light("Wedge", (2.2, 4.0, 3.8), 600.0, 5.5, (1.0, 0.70, 0.40), (-70, 0, 198))
+
+    cam_data = bpy.data.cameras.new("Cam")
+    cam_data.lens = 50.0
+    cam = bpy.data.objects.new("Cam", cam_data)
+    cam.location = (1.95, -2.55, 1.22)
+    scene.collection.objects.link(cam)
+    aim = bpy.data.objects.new("Aim", None)
+    aim.location = (0.0, 0.0, 0.40)
+    scene.collection.objects.link(aim)
+    con = cam.constraints.new("TRACK_TO")
+    con.target = aim
+    con.track_axis = "TRACK_NEGATIVE_Z"
+    con.up_axis = "UP_Y"
+    scene.camera = cam
+
+    scene.render.engine = "CYCLES" if engine == "cycles" else eevee_engine_id()
+    if engine == "cycles":
+        scene.cycles.samples = 32
+        scene.cycles.device = "CPU"
+    else:
+        try:
+            scene.eevee.taa_render_samples = 64
+        except AttributeError:
+            pass
+    scene.render.resolution_x = 1280
+    scene.render.resolution_y = 720
+    scene.render.image_settings.file_format = (
+        "WEBP" if path.lower().endswith(".webp") else "PNG"
+    )
+    if path.lower().endswith(".webp"):
+        scene.render.image_settings.quality = 90
+    scene.render.filepath = path
+    scene.view_settings.view_transform = "Standard"
+
+    fcode = gallery_framing.check_framing(
+        scene, cam, hero=[low], elements=[low], stage=[floor, wall],
+    )
+    if fcode:
+        return fcode
+    bpy.ops.render.render(write_still=True)
+    if not (os.path.exists(path) and os.path.getsize(path) > 0):
+        return fail("render produced no file", 14)
+    return 0
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    p = argparse.ArgumentParser()
+    p.add_argument("--output", default=None)
+    p.add_argument("--engine", default="eevee", choices=("eevee", "cycles"))
+    p.add_argument(
+        "--skip-decimate",
+        action="store_true",
+        help="falsification: skip the LOD DECIMATE stage",
+    )
+    args = p.parse_args(argv)
+
+    code, low, _high, wood, tex, _col = check(args.skip_decimate)
+    if code:
+        return code
+    if args.output:
+        rcode = render_still(low, wood, tex, os.path.abspath(args.output), args.engine)
+        if rcode:
+            return rcode
+        print(f"rendered still {args.output}")
+    print("park-bench OK")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except Exception as e:
+        traceback.print_exc()
+        print(f"FATAL: {e}", file=sys.stderr)
+        sys.exit(1)
diff --git a/showcase/park-bench/preview.webp b/showcase/park-bench/preview.webp
new file mode 100644
index 0000000..e7523f0
Binary files /dev/null and b/showcase/park-bench/preview.webp differ
diff --git a/showcase/wheelbarrow/README.md b/showcase/wheelbarrow/README.md
new file mode 100644
index 0000000..8d9e93f
--- /dev/null
+++ b/showcase/wheelbarrow/README.md
@@ -0,0 +1,74 @@
+# Wheelbarrow
+
+A showcase piece, not an example. Procedural wooden wheelbarrow (staved
+U-tray, iron straps, single spoked wheel, rear legs, handles) then the
+shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD
+chain, convex collider, Unity glTF export.
+
+It asserts **budget conformance** of the generated result. It does not
+witness an API contract. "It rendered without error" is not a check.
+
+**Composes** skills `mesh-editing-and-bmesh`, `bake-high-to-low`,
+`depsgraph-and-evaluated-data`, `engine-export-presets`, and snippets
+`bake_normal_high_to_low.py`, `setup_bake_target_image.py`,
+`lod_chain.py` / `decimate_to_budget.py`, `convex_hull_collider.py`,
+`export_preset_unity.py` (helpers copied, not imported as a package).
+
+## Budgets
+
+Declared as named constants; every gate **recomputes** from the mesh,
+materials, UVs, evaluated LOD, collider, or export file.
+
+| Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) |
+| --- | --- | --- |
+| Base triangles | 2980–3200 | 3088 / 3088 / 3088 |
+| LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.5000 |
+| LOD2 ratio | 0.10–0.35 of base | 0.2196 / 0.2196 / 0.2014 |
+| Materials | exactly 2 distinct, ≥24 metal faces | 2 slots, 308 metal |
+| UVs | in `0..1`, AABB overlap ≤ 1e-5 | in range, overlap 0 |
+| Outer AABB | (1.418, 0.463, 0.594) m ± 0.01 | (1.4176, 0.4627, 0.5937), zmin 0 |
+| Collider tris | ≤ 140 | 106 |
+| Export | written, size > 0 | 227404 / 227404 / 227388 bytes |
+
+DECIMATE COLLAPSE triangle counts are **not** identical across series —
+5.2.1 is more aggressive on LOD2. The gate is a ratio band, not an
+exact count. Bake pixels are stochastic; the gate is `has_data` plus
+operator `FINISHED`, not byte-identity. Construction uses no RNG.
+Export byte counts differ by 16 B on 5.2.1 (glTF serializer), not a
+gated axis.
+
+`--skip-decimate` skips the LOD DECIMATE stage so LOD1 ratio is 1.0 and
+exit 9 fires. That is the named budget the falsifier violates.
+
+## Run
+
+```bash
+blender --background --python wheelbarrow.py --
+blender --background --python wheelbarrow.py -- --skip-decimate
+blender --background --python wheelbarrow.py -- --output barrow.png
+```
+
+Smoke does not pass `--output` or `--skip-decimate`.
+
+## Exit codes
+
+File-local. `9` is a valid check code. `10` is reserved for
+`gallery_framing.check_framing` on the `--output` path.
+
+| Code | Meaning |
+| --- | --- |
+| 0 | Success |
+| 1 | Uncaught exception (FATAL wrapper) |
+| 2 | argparse / usage |
+| 3 | Mesh did not build / no UV layer |
+| 4 | Base triangle count outside range |
+| 5 | Material count ≠ 2 distinct slots, or wood/metal faces missing |
+| 6 | UVs outside 0..1 |
+| 7 | UV AABB overlap above tolerance |
+| 8 | World AABB off declared outer size |
+| 9 | LOD ratio band (`--skip-decimate` lands here) |
+| 10 | Framing gate (render path only) |
+| 11 | Collider triangle count above ceiling |
+| 12 | Bake did not finish or image has no data |
+| 13 | Export file missing or empty |
+| 14 | `--output` produced no file |
diff --git a/showcase/wheelbarrow/preview.webp b/showcase/wheelbarrow/preview.webp
new file mode 100644
index 0000000..acf25d4
Binary files /dev/null and b/showcase/wheelbarrow/preview.webp differ
diff --git a/showcase/wheelbarrow/wheelbarrow.py b/showcase/wheelbarrow/wheelbarrow.py
new file mode 100644
index 0000000..c9e12a3
--- /dev/null
+++ b/showcase/wheelbarrow/wheelbarrow.py
@@ -0,0 +1,877 @@
+"""Game-ready wooden wheelbarrow — a showcase piece, not an example.
+
+Asserts budget conformance of a procedural wheelbarrow (staved U-tray,
+iron straps, single spoked wheel, rear legs, handles) after composing
+shipped pipeline pieces: bmesh construction, UVs, two materials,
+high-to-low normal bake, LOD chain, convex collider, Unity glTF export.
+
+Budgets are declared below and recomputed from the generated result.
+They are not API-contract witnesses. ``--skip-decimate`` skips the LOD
+DECIMATE stage so the LOD-ratio budget fails.
+
+No RNG. Construction is closed-form. DECIMATE COLLAPSE triangle counts
+are not byte-identical across Blender versions — the LOD gate is a
+ratio band, not an exact count.
+
+    blender --background --python wheelbarrow.py --
+    blender --background --python wheelbarrow.py -- --skip-decimate
+    blender --background --python wheelbarrow.py -- --output barrow.png
+"""
+import argparse
+import math
+import os
+import sys
+import tempfile
+import traceback
+
+import bmesh
+import bpy
+from mathutils import Euler, Vector
+
+_REPO = os.path.abspath(
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir, os.pardir)
+)
+sys.path.insert(0, os.path.join(_REPO, "examples"))
+sys.dont_write_bytecode = True
+import gallery_framing  # noqa: E402
+
+RIM_MAJOR = 0.155
+RIM_MINOR = 0.020
+HUB_R = 0.028
+HUB_W = 0.038
+N_SPOKES = 8
+SPOKE_T = 0.014
+TRAY_L = 0.70
+TRAY_R = 0.205
+STAVE_T = 0.028
+N_STAVES = 7
+A_SPAN = 1.38
+HANDLE_L = 0.50
+IRON_T = 0.014
+
+BBOX_TOL = 0.01
+OUTER_SIZE = (1.418, 0.463, 0.594)
+BASE_TRIS_MIN = 2980
+BASE_TRIS_MAX = 3200
+LOD1_RATIO_MIN = 0.32
+LOD1_RATIO_MAX = 0.62
+LOD2_RATIO_MIN = 0.10
+LOD2_RATIO_MAX = 0.35
+LOD1_TARGET = 0.50
+LOD2_TARGET = 0.22
+MATERIAL_COUNT = 2
+UV_EPS = 1e-4
+UV_OVERLAP_MAX = 1e-5
+COLLIDER_TRIS_MAX = 140
+BAKE_RES = 256
+CAGE_EXTRUSION = 0.08
+METAL_FACES_MIN = 24
+WOOD_FACES_MIN = 24
+
+WOOD_IDX = 0
+METAL_IDX = 1
+
+
+def eevee_engine_id():
+    return "BLENDER_EEVEE" if bpy.app.version >= (5, 0, 0) else "BLENDER_EEVEE_NEXT"
+
+
+def fail(msg, code):
+    print(f"ERROR: {msg}", file=sys.stderr)
+    return code
+
+
+def triangle_count(mesh):
+    mesh.calc_loop_triangles()
+    return len(mesh.loop_triangles)
+
+
+def evaluated_triangle_count(obj):
+    depsgraph = bpy.context.evaluated_depsgraph_get()
+    eval_obj = obj.evaluated_get(depsgraph)
+    eval_mesh = eval_obj.to_mesh()
+    try:
+        eval_mesh.calc_loop_triangles()
+        return len(eval_mesh.loop_triangles)
+    finally:
+        eval_obj.to_mesh_clear()
+
+
+def deselect_all():
+    for ob in list(bpy.context.view_layer.objects):
+        if ob is None:
+            continue
+        ob.select_set(False)
+
+
+def add_box(bm, loc, scale, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cube(bm, size=1.0)
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        p = Vector((v.co.x * scale[0], v.co.y * scale[1], v.co.z * scale[2]))
+        v.co = rot @ p + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_oriented_box(bm, a, b, scale_xy, mat_idx):
+    a = Vector(a)
+    b = Vector(b)
+    delta = b - a
+    length = delta.length
+    if length < 1e-8:
+        return []
+    quat = Vector((0.0, 0.0, 1.0)).rotation_difference(delta.normalized())
+    eul = quat.to_euler("XYZ")
+    return add_box(
+        bm,
+        ((a + b) * 0.5),
+        (scale_xy[0], scale_xy[1], length),
+        mat_idx,
+        euler=(eul.x, eul.y, eul.z),
+    )
+
+
+def add_cyl(bm, loc, radius, depth, segments, mat_idx, euler=(0.0, 0.0, 0.0)):
+    geo = bmesh.ops.create_cone(
+        bm,
+        cap_ends=True,
+        cap_tris=False,
+        segments=segments,
+        radius1=radius,
+        radius2=radius,
+        depth=depth,
+    )
+    verts = geo["verts"]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        v.co = rot @ v.co + origin
+    faces = {f for v in verts for f in v.link_faces}
+    for f in faces:
+        f.material_index = mat_idx
+    return verts
+
+
+def add_rim(bm, loc, major, minor, mat_idx, euler=(0.0, 0.0, 0.0)):
+    n_major = 16
+    n_minor = 8
+    rings = []
+    for i in range(n_major):
+        u = i * (2.0 * math.pi / n_major)
+        ring = []
+        for j in range(n_minor):
+            v = j * (2.0 * math.pi / n_minor)
+            x = (major + minor * math.cos(v)) * math.cos(u)
+            y = (major + minor * math.cos(v)) * math.sin(u)
+            z = minor * math.sin(v)
+            ring.append(bm.verts.new((x, y, z)))
+        rings.append(ring)
+    bm.verts.ensure_lookup_table()
+    for i in range(n_major):
+        i2 = (i + 1) % n_major
+        for j in range(n_minor):
+            j2 = (j + 1) % n_minor
+            face = bm.faces.new(
+                (rings[i][j], rings[i2][j], rings[i2][j2], rings[i][j2])
+            )
+            face.material_index = mat_idx
+    verts = [v for ring in rings for v in ring]
+    rot = Euler(euler).to_matrix()
+    origin = Vector(loc)
+    for v in verts:
+        v.co = rot @ v.co + origin
+    return verts
+
+
+def add_wheel_wood(bm, loc, wood):
+    wood.extend(
+        add_rim(bm, loc, RIM_MAJOR, RIM_MINOR, WOOD_IDX, euler=(math.pi / 2.0, 0.0, 0.0))
+    )
+    wood.extend(
+        add_cyl(
+            bm,
+            loc,
+            HUB_R,
+            HUB_W,
+            12,
+            WOOD_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    inner = HUB_R + 0.008
+    outer = RIM_MAJOR - RIM_MINOR * 0.55
+    mid_r = 0.5 * (inner + outer)
+    slen = outer - inner
+    for i in range(N_SPOKES):
+        a = i * (2.0 * math.pi / N_SPOKES)
+        dx = math.cos(a)
+        dz = math.sin(a)
+        cx = loc[0] + dx * mid_r
+        cy = loc[1]
+        cz = loc[2] + dz * mid_r
+        wood.extend(
+            add_box(
+                bm,
+                (cx, cy, cz),
+                (slen, SPOKE_T * 0.85, SPOKE_T),
+                WOOD_IDX,
+                euler=(0.0, -a, 0.0),
+            )
+        )
+
+
+def add_wheel_metal(bm, loc, metal):
+    metal.extend(
+        add_rim(
+            bm,
+            loc,
+            RIM_MAJOR + 0.004,
+            RIM_MINOR * 0.45,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    metal.extend(
+        add_cyl(
+            bm,
+            loc,
+            HUB_R + 0.010,
+            0.016,
+            12,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+    metal.extend(
+        add_cyl(
+            bm,
+            loc,
+            0.014,
+            0.10,
+            8,
+            METAL_IDX,
+            euler=(math.pi / 2.0, 0.0, 0.0),
+        )
+    )
+
+
+def pack_uvs(bm, margin=0.08):
+    uv = bm.loops.layers.uv.new("UVMap")
+    faces = list(bm.faces)
+    n = len(faces)
+    cols = max(1, math.ceil(math.sqrt(n)))
+    rows = max(1, math.ceil(n / cols))
+    cell_w = 1.0 / cols
+    cell_h = 1.0 / rows
+    pad_u = margin * cell_w * 0.5
+    pad_v = margin * cell_h * 0.5
+    usable_w = cell_w - 2.0 * pad_u
+    usable_h = cell_h - 2.0 * pad_v
+    for i, face in enumerate(faces):
+        col = i % cols
+        row = i // cols
+        nrm = face.normal
+        ax = abs(nrm.x)
+        ay = abs(nrm.y)
+        az = abs(nrm.z)
+        coords = []
+        for loop in face.loops:
+            co = loop.vert.co
+            if az >= ax and az >= ay:
+                coords.append((co.x, co.y))
+            elif ax >= ay:
+                coords.append((co.y, co.z))
+            else:
+                coords.append((co.x, co.z))
+        xs = [c[0] for c in coords]
+        ys = [c[1] for c in coords]
+        minx, maxx = min(xs), max(xs)
+        miny, maxy = min(ys), max(ys)
+        dx = max(maxx - minx, 1e-8)
+        dy = max(maxy - miny, 1e-8)
+        origin_u = col * cell_w + pad_u
+        origin_v = row * cell_h + pad_v
+        for loop, (x, y) in zip(face.loops, coords):
+            loop[uv].uv = (
+                origin_u + (x - minx) / dx * usable_w,
+                origin_v + (y - miny) / dy * usable_h,
+            )
+
+
+def build_barrow_mesh(name, bevel_offset, bevel_segments):
+    bm = bmesh.new()
+    try:
+        wood = []
+        metal = []
+        zc = 0.26 + TRAY_R
+        cx = 0.0
+
+        def pt(a, x):
+            return (
+                x,
+                TRAY_R * math.sin(a),
+                zc - TRAY_R * math.cos(a),
+            )
+
+        gap = 0.12
+        for i in range(N_STAVES):
+            t0 = i / N_STAVES
+            t1 = (i + (1.0 - gap)) / N_STAVES
+            a0 = -A_SPAN + 2.0 * A_SPAN * t0
+            a1 = -A_SPAN + 2.0 * A_SPAN * t1
+            mid = 0.5 * (a0 + a1)
+            chord = TRAY_R * abs(a1 - a0) * 0.95
+            wood.extend(
+                add_box(
+                    bm,
+                    pt(mid, cx),
+                    (TRAY_L, chord, STAVE_T),
+                    WOOD_IDX,
+                    euler=(mid, 0.0, 0.0),
+                )
+            )
+            wood.extend(
+                add_box(
+                    bm,
+                    pt(mid, cx + TRAY_L / 2.0 + 0.014),
+                    (0.028, chord * 1.02, STAVE_T * 1.05),
+                    WOOD_IDX,
+                    euler=(mid, 0.0, 0.0),
+                )
+            )
+
+        rim_y = TRAY_R * math.sin(A_SPAN)
+        rim_z = zc - TRAY_R * math.cos(A_SPAN)
+        for ysign in (-1.0, 1.0):
+            start = (
+                cx - TRAY_L / 2.0 + 0.05,
+                ysign * rim_y,
+                rim_z,
+            )
+            end = (
+                cx - TRAY_L / 2.0 - HANDLE_L,
+                ysign * (rim_y + 0.015),
+                0.56,
+            )
+            wood.extend(
+                add_oriented_box(bm, start, end, (0.030, 0.030), WOOD_IDX)
+            )
+
+        lx = cx - TRAY_L * 0.30
+        for ysign in (-1.0, 1.0):
+            top = (lx, ysign * 0.11, zc - TRAY_R * 0.35)
+            bot = (lx - 0.03, ysign * 0.18, 0.02)
+            wood.extend(add_oriented_box(bm, top, bot, (0.034, 0.034), WOOD_IDX))
+        wood.extend(
+            add_oriented_box(
+                bm,
+                (lx, -0.15, 0.13),
+                (lx, 0.15, 0.13),
+                (0.026, 0.026),
+                WOOD_IDX,
+            )
+        )
+
+        if bevel_offset > 0.0:
+            edges = list({e for v in wood for e in v.link_edges})
+            ret = bmesh.ops.bevel(
+                bm,
+                geom=edges,
+                offset=bevel_offset,
+                segments=bevel_segments,
+                profile=0.5,
+                affect="EDGES",
+                clamp_overlap=True,
+            )
+            for f in ret.get("faces") or []:
+                f.material_index = WOOD_IDX
+
+        wx = cx + TRAY_L / 2.0 + 0.04
+        wz = RIM_MAJOR
+        add_wheel_wood(bm, (wx, 0.0, wz), wood)
+        add_wheel_metal(bm, (wx, 0.0, wz), metal)
+
+        r_strap = TRAY_R + STAVE_T * 0.55 + 0.004
+        for sx in (-TRAY_L * 0.28, TRAY_L * 0.22):
+            n = 11
+            pts = []
+            for k in range(n + 1):
+                a = -A_SPAN + 2.0 * A_SPAN * k / n
+                pts.append(
+                    (
+                        cx + sx,
+                        r_strap * math.sin(a),
+                        zc - r_strap * math.cos(a),
+                    )
+                )
+            for p0, p1 in zip(pts, pts[1:]):
+                metal.extend(
+                    add_oriented_box(bm, p0, p1, (0.018, 0.010), METAL_IDX)
+                )
+
+        fy = 0.045
+        for ysign in (-1.0, 1.0):
+            metal.extend(
+                add_oriented_box(
+                    bm,
+                    (cx + TRAY_L / 2.0 - 0.05, ysign * fy, zc - TRAY_R * 0.55),
+                    (wx, ysign * fy, wz),
+                    (0.016, 0.016),
+                    METAL_IDX,
+                )
+            )
+            metal.extend(
+                add_box(
+                    bm,
+                    (lx - 0.03, ysign * 0.18, 0.012),
+                    (0.055, 0.042, 0.022),
+                    METAL_IDX,
+                )
+            )
+
+        xs = [v.co.x for v in bm.verts]
+        ys = [v.co.y for v in bm.verts]
+        zs = [v.co.z for v in bm.verts]
+        rcx = 0.5 * (min(xs) + max(xs))
+        rcy = 0.5 * (min(ys) + max(ys))
+        zmin = min(zs)
+        for v in bm.verts:
+            v.co.x -= rcx
+            v.co.y -= rcy
+            v.co.z -= zmin
+            if v.co.z < 0.0:
+                v.co.z = 0.0
+
+        pack_uvs(bm)
+        bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
+        for face in bm.faces:
+            face.smooth = False
+        me = bpy.data.meshes.new(name)
+        bm.to_mesh(me)
+        me.update()
+        for poly in me.polygons:
+            poly.use_smooth = False
+    finally:
+        bm.free()
+    out = bpy.data.objects.new(name, me)
+    bpy.context.collection.objects.link(out)
+    return out
+
+
+def principled(name, color, metallic, roughness):
+    mat = bpy.data.materials.new(name)
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes["Principled BSDF"]
+    bsdf.inputs["Base Color"].default_value = color
+    bsdf.inputs["Metallic"].default_value = metallic
+    bsdf.inputs["Roughness"].default_value = roughness
+    return mat
+
+
+def assign_slots(obj, wood, metal):
+    mats = obj.data.materials
+    wanted = (wood, metal)
+    for i, mat in enumerate(wanted):
+        if i < len(mats):
+            mats[i] = mat
+        else:
+            mats.append(mat)
+
+
+def world_bbox(obj):
+    corners = [obj.matrix_world @ Vector(c) for c in obj.bound_box]
+    xs = [c.x for c in corners]
+    ys = [c.y for c in corners]
+    zs = [c.z for c in corners]
+    return (min(xs), min(ys), min(zs), max(xs), max(ys), max(zs))
+
+
+def uv_stats(mesh):
+    uv = mesh.uv_layers.active
+    if uv is None:
+        return 0.0, 0.0, 1.0, 1.0, 0, 1.0
+    data = uv.data
+    us = [loop.uv[0] for loop in data]
+    vs = [loop.uv[1] for loop in data]
+    aabbs = []
+    for poly in mesh.polygons:
+        pu = [data[i].uv[0] for i in poly.loop_indices]
+        pv = [data[i].uv[1] for i in poly.loop_indices]
+        aabbs.append((min(pu), min(pv), max(pu), max(pv)))
+    overlap = 0.0
+    for i in range(len(aabbs)):
+        a = aabbs[i]
+        for j in range(i + 1, len(aabbs)):
+            b = aabbs[j]
+            x0 = max(a[0], b[0])
+            y0 = max(a[1], b[1])
+            x1 = min(a[2], b[2])
+            y1 = min(a[3], b[3])
+            overlap += max(0.0, x1 - x0) * max(0.0, y1 - y0)
+    return min(us), min(vs), max(us), max(vs), overlap, len(aabbs)
+
+
+def make_lod(obj, name, ratio, skip_decimate):
+    mesh = obj.data.copy()
+    lod = bpy.data.objects.new(name, mesh)
+    lod.matrix_world = obj.matrix_world.copy()
+    bpy.context.scene.collection.objects.link(lod)
+    if not skip_decimate and 0.0 < ratio < 1.0:
+        mod = lod.modifiers.new("DecimateBudget", "DECIMATE")
+        mod.decimate_type = "COLLAPSE"
+        mod.ratio = ratio
+    return lod
+
+
+def convex_hull_collider(obj, name):
+    mesh = bpy.data.meshes.new(name)
+    bm = bmesh.new()
+    try:
+        bm.from_mesh(obj.data)
+        result = bmesh.ops.convex_hull(bm, input=list(bm.verts))
+        interior = result.get("geom_interior") or []
+        unused = result.get("geom_unused") or []
+        if interior:
+            bmesh.ops.delete(bm, geom=interior, context="VERTS")
+        if unused:
+            bmesh.ops.delete(bm, geom=unused, context="VERTS")
+        bm.to_mesh(mesh)
+        mesh.update()
+    finally:
+        bm.free()
+    collider = bpy.data.objects.new(name, mesh)
+    bpy.context.collection.objects.link(collider)
+    collider.matrix_world = obj.matrix_world.copy()
+    return collider
+
+
+def setup_bake_image(obj, target_mat, size=BAKE_RES):
+    if not obj.data.uv_layers:
+        return None, None
+    img = bpy.data.images.new("BarrowNrm", size, size, alpha=True, float_buffer=False)
+    img.colorspace_settings.name = "Non-Color"
+    nodes = target_mat.node_tree.nodes
+    tex = nodes.new("ShaderNodeTexImage")
+    tex.image = img
+    nodes.active = tex
+    tex.select = True
+    obj.active_material_index = WOOD_IDX
+    return img, tex
+
+
+def bake_normal(high, low):
+    scene = bpy.context.scene
+    scene.render.engine = "CYCLES"
+    scene.cycles.device = "CPU"
+    scene.cycles.samples = 1
+    scene.cycles.use_denoising = False
+    deselect_all()
+    high.select_set(True)
+    low.select_set(True)
+    bpy.context.view_layer.objects.active = low
+    return bpy.ops.object.bake(
+        type="NORMAL",
+        use_selected_to_active=True,
+        cage_extrusion=CAGE_EXTRUSION,
+        use_cage=False,
+        normal_space="TANGENT",
+        margin=4,
+        margin_type="ADJACENT_FACES",
+        use_clear=True,
+        target="IMAGE_TEXTURES",
+    )
+
+
+def export_unity(path, objects):
+    deselect_all()
+    for ob in objects:
+        ob.select_set(True)
+    bpy.context.view_layer.objects.active = objects[0]
+    bpy.ops.export_scene.gltf(
+        filepath=path,
+        use_selection=True,
+        export_yup=True,
+        export_apply=True,
+        export_draco_mesh_compression_enable=False,
+        export_animations=False,
+    )
+
+
+def check(skip_decimate):
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    low = build_barrow_mesh("BarrowLow", bevel_offset=0.005, bevel_segments=2)
+    high = build_barrow_mesh("BarrowHigh", bevel_offset=0.005, bevel_segments=4)
+    wood = principled("BarrowWood", (0.38, 0.21, 0.09, 1.0), 0.0, 0.58)
+    metal = principled("BarrowIron", (0.10, 0.105, 0.12, 1.0), 1.0, 0.30)
+    assign_slots(low, wood, metal)
+    assign_slots(high, wood, metal)
+
+    if low.data is None or len(low.data.polygons) < 6:
+        return fail("barrow mesh did not build", 3), None, None, None, None, None
+
+    base_tris = triangle_count(low.data)
+    mats = [s for s in low.data.materials if s is not None]
+    nmat = len(mats)
+    distinct_mats = len({id(s) for s in mats})
+    idx_counts = {}
+    for poly in low.data.polygons:
+        idx_counts[poly.material_index] = idx_counts.get(poly.material_index, 0) + 1
+    print(f"measured mat_index_counts={idx_counts}")
+    u0, v0, u1, v1, overlap, nfaces = uv_stats(low.data)
+    bb = world_bbox(low)
+    size_x = bb[3] - bb[0]
+    size_y = bb[4] - bb[1]
+    size_z = bb[5] - bb[2]
+
+    img, tex = setup_bake_image(low, wood)
+    if img is None:
+        return fail("barrow has no UV layer", 3), None, None, None, None, None
+    bake_result = bake_normal(high, low)
+
+    lod1 = make_lod(low, "BarrowLOD1", LOD1_TARGET, skip_decimate)
+    lod2 = make_lod(low, "BarrowLOD2", LOD2_TARGET, skip_decimate)
+    bpy.context.view_layer.update()
+    lod1_tris = evaluated_triangle_count(lod1)
+    lod2_tris = evaluated_triangle_count(lod2)
+    r1 = lod1_tris / base_tris if base_tris else 0.0
+    r2 = lod2_tris / base_tris if base_tris else 0.0
+
+    collider_src = build_barrow_mesh("BarrowColSrc", bevel_offset=0.0, bevel_segments=1)
+    collider = convex_hull_collider(collider_src, "BarrowCollider")
+    bpy.data.objects.remove(collider_src, do_unlink=True)
+    col_tris = triangle_count(collider.data)
+
+    export_path = os.path.join(
+        tempfile.gettempdir(),
+        f"bdt_wheelbarrow_{os.getpid()}.glb",
+    )
+    if os.path.exists(export_path):
+        os.remove(export_path)
+    export_unity(export_path, [low, collider])
+    export_size = os.path.getsize(export_path) if os.path.isfile(export_path) else 0
+
+    print(f"blender={tuple(bpy.app.version)} skip_decimate={skip_decimate}")
+    print(
+        f"measured base_tris={base_tris} lod1_tris={lod1_tris} "
+        f"lod2_tris={lod2_tris} r1={r1:.4f} r2={r2:.4f}"
+    )
+    print(
+        f"measured nmat={nmat} uv=({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f}) "
+        f"overlap={overlap:.6f} nfaces={nfaces}"
+    )
+    print(
+        f"measured bbox=({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+        f"outer={OUTER_SIZE} zmin={bb[2]:.4f}"
+    )
+    print(
+        f"measured collider_tris={col_tris} bake={bake_result} "
+        f"bake_has_data={img.has_data} export_bytes={export_size}"
+    )
+
+    if not (BASE_TRIS_MIN <= base_tris <= BASE_TRIS_MAX):
+        return fail(
+            f"base tris {base_tris} not in [{BASE_TRIS_MIN}, {BASE_TRIS_MAX}]",
+            4,
+        ), None, None, None, None, None
+    if nmat != MATERIAL_COUNT or distinct_mats != MATERIAL_COUNT:
+        return fail(
+            f"material slots {nmat} distinct {distinct_mats} != {MATERIAL_COUNT}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(METAL_IDX, 0) < METAL_FACES_MIN:
+        return fail(
+            f"metal faces {idx_counts.get(METAL_IDX, 0)} < {METAL_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if idx_counts.get(WOOD_IDX, 0) < WOOD_FACES_MIN:
+        return fail(
+            f"wood faces {idx_counts.get(WOOD_IDX, 0)} < {WOOD_FACES_MIN}",
+            5,
+        ), None, None, None, None, None
+    if u0 < -UV_EPS or v0 < -UV_EPS or u1 > 1.0 + UV_EPS or v1 > 1.0 + UV_EPS:
+        return fail(
+            f"UVs outside 0..1: ({u0:.4f},{v0:.4f})-({u1:.4f},{v1:.4f})",
+            6,
+        ), None, None, None, None, None
+    if overlap > UV_OVERLAP_MAX:
+        return fail(
+            f"UV AABB overlap {overlap:.6f} > {UV_OVERLAP_MAX}",
+            7,
+        ), None, None, None, None, None
+    if (
+        abs(size_x - OUTER_SIZE[0]) > BBOX_TOL
+        or abs(size_y - OUTER_SIZE[1]) > BBOX_TOL
+        or abs(size_z - OUTER_SIZE[2]) > BBOX_TOL
+    ):
+        return fail(
+            f"bbox ({size_x:.4f},{size_y:.4f},{size_z:.4f}) "
+            f"off outer {OUTER_SIZE}",
+            8,
+        ), None, None, None, None, None
+    if not (LOD1_RATIO_MIN <= r1 <= LOD1_RATIO_MAX):
+        return fail(
+            f"LOD1 ratio {r1:.4f} not in [{LOD1_RATIO_MIN}, {LOD1_RATIO_MAX}] "
+            "(--skip-decimate is the designed fail)",
+            9,
+        ), None, None, None, None, None
+    if not (LOD2_RATIO_MIN <= r2 <= LOD2_RATIO_MAX):
+        return fail(
+            f"LOD2 ratio {r2:.4f} not in [{LOD2_RATIO_MIN}, {LOD2_RATIO_MAX}]",
+            9,
+        ), None, None, None, None, None
+    if col_tris > COLLIDER_TRIS_MAX:
+        return fail(
+            f"collider tris {col_tris} > {COLLIDER_TRIS_MAX}",
+            11,
+        ), None, None, None, None, None
+    if bake_result != {"FINISHED"} or not img.has_data:
+        return fail(
+            f"bake failed result={bake_result} has_data={img.has_data}",
+            12,
+        ), None, None, None, None, None
+    if export_size <= 0:
+        return fail("export file missing or empty", 13), None, None, None, None, None
+    return 0, low, high, wood, tex, collider
+
+
+def wire_normal(mat, tex):
+    nt = mat.node_tree
+    bsdf = nt.nodes["Principled BSDF"]
+    nrm = nt.nodes.new("ShaderNodeNormalMap")
+    nrm.inputs["Strength"].default_value = 1.0
+    nt.links.new(tex.outputs["Color"], nrm.inputs["Color"])
+    nt.links.new(nrm.outputs["Normal"], bsdf.inputs["Normal"])
+
+
+def render_still(low, wood, tex, path, engine):
+    scene = bpy.context.scene
+    wire_normal(wood, tex)
+    for ob in list(scene.objects):
+        if ob.type == "MESH" and ob != low:
+            ob.hide_render = True
+            ob.hide_viewport = True
+
+    low.rotation_euler.z = math.radians(-32.0)
+    low.rotation_euler.x = math.radians(0.0)
+
+    floor_me = bpy.data.meshes.new("Floor")
+    bm = bmesh.new()
+    try:
+        bmesh.ops.create_grid(bm, x_segments=1, y_segments=1, size=14.0)
+        bm.to_mesh(floor_me)
+    finally:
+        bm.free()
+    fmat = bpy.data.materials.new("Floor")
+    fmat.use_nodes = True
+    fb = fmat.node_tree.nodes["Principled BSDF"]
+    fb.inputs["Base Color"].default_value = (0.03, 0.032, 0.037, 1.0)
+    fb.inputs["Roughness"].default_value = 0.7
+    floor_me.materials.append(fmat)
+    floor = bpy.data.objects.new("Floor", floor_me)
+    scene.collection.objects.link(floor)
+    wall = bpy.data.objects.new("Wall", floor_me.copy())
+    wall.location = (0.0, 8.5, 0.0)
+    wall.rotation_euler = (math.radians(90), 0.0, 0.0)
+    scene.collection.objects.link(wall)
+
+    world = bpy.data.worlds.new("World")
+    world.use_nodes = True
+    world.node_tree.nodes["Background"].inputs["Color"].default_value = (
+        0.02, 0.021, 0.025, 1.0,
+    )
+    scene.world = world
+
+    def light(name, loc, energy, size, col, rot):
+        ld = bpy.data.lights.new(name, "AREA")
+        ld.energy = energy
+        ld.size = size
+        ld.color = col
+        ob = bpy.data.objects.new(name, ld)
+        ob.location = loc
+        ob.rotation_euler = tuple(math.radians(a) for a in rot)
+        scene.collection.objects.link(ob)
+
+    light("Key", (-3.6, -5.0, 5.4), 660.0, 4.0, (1.0, 0.94, 0.86), (50, 0, -36))
+    light("Fill", (5.0, -3.4, 2.4), 46.0, 8.0, (0.72, 0.82, 1.0), (62, 0, 50))
+    light("Wedge", (2.2, 4.0, 3.8), 600.0, 5.5, (1.0, 0.70, 0.40), (-70, 0, 198))
+
+    cam_data = bpy.data.cameras.new("Cam")
+    cam_data.lens = 50.0
+    cam = bpy.data.objects.new("Cam", cam_data)
+    cam.location = (1.82, -2.22, 1.12)
+    scene.collection.objects.link(cam)
+    aim = bpy.data.objects.new("Aim", None)
+    aim.location = (0.0, 0.0, 0.34)
+    scene.collection.objects.link(aim)
+    con = cam.constraints.new("TRACK_TO")
+    con.target = aim
+    con.track_axis = "TRACK_NEGATIVE_Z"
+    con.up_axis = "UP_Y"
+    scene.camera = cam
+
+    scene.render.engine = "CYCLES" if engine == "cycles" else eevee_engine_id()
+    if engine == "cycles":
+        scene.cycles.samples = 32
+        scene.cycles.device = "CPU"
+    else:
+        try:
+            scene.eevee.taa_render_samples = 64
+        except AttributeError:
+            pass
+    scene.render.resolution_x = 1280
+    scene.render.resolution_y = 720
+    scene.render.image_settings.file_format = (
+        "WEBP" if path.lower().endswith(".webp") else "PNG"
+    )
+    if path.lower().endswith(".webp"):
+        scene.render.image_settings.quality = 90
+    scene.render.filepath = path
+    scene.view_settings.view_transform = "Standard"
+
+    fcode = gallery_framing.check_framing(
+        scene, cam, hero=[low], elements=[low], stage=[floor, wall],
+    )
+    if fcode:
+        return fcode
+    bpy.ops.render.render(write_still=True)
+    if not (os.path.exists(path) and os.path.getsize(path) > 0):
+        return fail("render produced no file", 14)
+    return 0
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    p = argparse.ArgumentParser()
+    p.add_argument("--output", default=None)
+    p.add_argument("--engine", default="eevee", choices=("eevee", "cycles"))
+    p.add_argument(
+        "--skip-decimate",
+        action="store_true",
+        help="falsification: skip the LOD DECIMATE stage",
+    )
+    args = p.parse_args(argv)
+
+    code, low, _high, wood, tex, _col = check(args.skip_decimate)
+    if code:
+        return code
+    if args.output:
+        rcode = render_still(low, wood, tex, os.path.abspath(args.output), args.engine)
+        if rcode:
+            return rcode
+        print(f"rendered still {args.output}")
+    print("wheelbarrow OK")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except Exception as e:
+        traceback.print_exc()
+        print(f"FATAL: {e}", file=sys.stderr)
+        sys.exit(1)
diff --git a/tests/smoke/catalog.json b/tests/smoke/catalog.json
index 30a08cf..5e08356 100644
--- a/tests/smoke/catalog.json
+++ b/tests/smoke/catalog.json
@@ -84,5 +84,7 @@
   {"name": "terrain-scatter", "script": "showcase/terrain-scatter/terrain_scatter.py"},
   {"name": "fence-kit", "script": "showcase/fence-kit/fence_kit.py"},
   {"name": "watchtower", "script": "showcase/watchtower/watchtower.py"},
-  {"name": "cart", "script": "showcase/cart/cart.py"}
+  {"name": "cart", "script": "showcase/cart/cart.py"},
+  {"name": "park-bench", "script": "showcase/park-bench/park_bench.py"},
+  {"name": "wheelbarrow", "script": "showcase/wheelbarrow/wheelbarrow.py"}
 ]