fix(showcase): grindstone and wheelbarrow visual quality pass

docs/gallery/index.html

@@ -1024,7 +1024,7 @@ <h2><a href="park-bench/">park-bench</a></h2>
         <div class="card-body">
           <h2><a href="wheelbarrow/">wheelbarrow</a></h2>
           <p class="teaches">A procedural wooden wheelbarrow through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.</p>
-          <p class="witnesses"><span class="tag">witnesses</span> 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.</p>
+          <p class="witnesses"><span class="tag">witnesses</span> Recomputed: 2500 tris, two materials with 1094 wood and 190 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.556×0.630×0.572 m, zmin 0, hygiene 0, wall-floor seat 12 mm, spoke clearance 40 mm, LOD ratios in band (5.2 COLLAPSE leaner on LOD2), convex collider 90 tris, non-empty glTF. --skip-decimate exits 9 on LOD1; --stray-vert exits 15 on hygiene; --lift-z / --short-legs exit 16 on grounded; --fat-spokes / --float-walls exit 17 on joint fit; --pipe-rim exits 18 on tread aspect.</p>
           <a class="card-link" href="wheelbarrow/">View example <span aria-hidden="true">&rarr;</span></a>
         </div>
       </article>
@@ -1068,7 +1068,7 @@ <h2><a href="hitching-post/">hitching-post</a></h2>
         <div class="card-body">
           <h2><a href="grindstone/">grindstone</a></h2>
           <p class="teaches">A procedural grindstone on a timber trestle through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.</p>
-          <p class="witnesses"><span class="tag">witnesses</span> Recomputed: 1604 tris, three materials with 80 metal and 26 stone faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.630×0.615×0.575 m, LOD ratios in band, convex collider 130 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.</p>
+          <p class="witnesses"><span class="tag">witnesses</span> Recomputed: 928 tris, three materials with 216 wood / 160 stone / 180 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.710×0.419×0.610 m, zmin 0, hygiene 0, four shoes planted, trough seated in the sills, stone dip 26 mm, LOD ratios in band (5.2 COLLAPSE leaner on LOD2), convex collider 198 tris, non-empty glTF. --skip-decimate exits 9 on LOD1; --stray-vert exits 15 on hygiene; --lift-z / --short-legs exit 16 on grounded; --float-crank / --float-legs exit 17 on joint fit; --no-dip / --narrow-trough exit 18 on seat.</p>
           <a class="card-link" href="grindstone/">View example <span aria-hidden="true">&rarr;</span></a>
         </div>
       </article>

showcase/README.md

@@ -53,6 +53,13 @@ entry in `showcase/gallery.json`, and a rendered still.
   single-shell contract. Pairs of parts meant to touch assert a BVH
   surface gap below a named epsilon (vert-vert is the wrong metric for
   thin straps and collars).
+- **Named supports (exit 16).** AABB `zmin` is necessary but not
+  sufficient on a multi-support prop: a wheel, a sled floor, or one
+  planted foot can ground the box while the other feet float. Split the
+  mesh into shells and assert each named support (shoe, tyre, foot) has
+  its own `zmin` within epsilon of 0. `--short-legs` (or the piece's
+  equivalent) is the falsifier: float the named supports while leaving
+  something else on the ground so the AABB gate would still pass.
 - **Joint-fit budgets.** Parts that interpenetrate on purpose — a tenon
   in a mortise, a peg in a hub — assert how deep the overlap goes, not
   just that it exists. Split the mesh into shells by edge connectivity,

showcase/gallery.json

@@ -153,7 +153,7 @@
       "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.",
+      "witnessesFix": "Recomputed: 2500 tris, two materials with 1094 wood and 190 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.556×0.630×0.572 m, zmin 0, hygiene 0, wall-floor seat 12 mm, spoke clearance 40 mm, LOD ratios in band (5.2 COLLAPSE leaner on LOD2), convex collider 90 tris, non-empty glTF. --skip-decimate exits 9 on LOD1; --stray-vert exits 15 on hygiene; --lift-z / --short-legs exit 16 on grounded; --fat-spokes / --float-walls exit 17 on joint fit; --pipe-rim exits 18 on tread aspect.",
       "hero": "docs/gallery/assets/wheelbarrow-hero.webp",
       "preview": "showcase/wheelbarrow/preview.webp",
       "tags": [
@@ -201,7 +201,7 @@
       "name": "grindstone",
       "dir": "showcase/grindstone",
       "teaches": "A procedural grindstone on a timber trestle through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.",
-      "witnessesFix": "Recomputed: 1604 tris, three materials with 80 metal and 26 stone faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.630×0.615×0.575 m, LOD ratios in band, convex collider 130 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.",
+      "witnessesFix": "Recomputed: 928 tris, three materials with 216 wood / 160 stone / 180 metal faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.710×0.419×0.610 m, zmin 0, hygiene 0, four shoes planted, trough seated in the sills, stone dip 26 mm, LOD ratios in band (5.2 COLLAPSE leaner on LOD2), convex collider 198 tris, non-empty glTF. --skip-decimate exits 9 on LOD1; --stray-vert exits 15 on hygiene; --lift-z / --short-legs exit 16 on grounded; --float-crank / --float-legs exit 17 on joint fit; --no-dip / --narrow-trough exit 18 on seat.",
       "hero": "docs/gallery/assets/grindstone-hero.webp",
       "preview": "showcase/grindstone/preview.webp",
       "tags": [

showcase/grindstone/README.md

@@ -1,9 +1,14 @@
 # Grindstone
 
-A showcase piece, not an example. Procedural grindstone (stone wheel,
-timber A-frame trestle, iron axle, hubs, crank, and tray) then the
-shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD
-chain, convex collider, Unity glTF export.
+A showcase piece, not an example. Procedural grindstone (sandstone
+wheel, timber A-frame trestle, iron shoes/axle/hubs/crank, open water
+trough) then the shipped pipeline: unique-cell UVs, Cycles high-to-low
+normal bake, LOD chain, convex collider, Unity glTF export.
+
+The A-frame is a king post with diagonals tenoning into a fatter sill,
+not two sticks meeting at a point. The trough is one manifold basin
+seated into those sills. Iron shoes bury a short wood tenon so the
+angled leg end-cap cannot pierce Z=0.
 
 It asserts **budget conformance** of the generated result. It does not
 witness an API contract. "It rendered without error" is not a check.
@@ -21,38 +26,85 @@ materials, UVs, evaluated LOD, collider, or export file.
 
 | Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) |
 | --- | --- | --- |
-| Base triangles | 1480–1720 | 1604 / 1604 / 1604 |
+| Base triangles | 700–1000 | 928 / 928 / 928 |
 | LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.5000 |
-| LOD2 ratio | 0.10–0.35 of base | 0.2195 / 0.2195 / 0.2195 |
-| Materials | exactly 3 distinct, ≥24 metal and stone faces | 3 slots, 80 metal, 26 stone |
+| LOD2 ratio | 0.10–0.35 of base | 0.2198 / 0.2198 / 0.1897 |
+| Materials | exactly 3 distinct; ≥80 wood, stone, metal faces | 3 slots; 216 / 160 / 180 |
 | UVs | in `0..1`, AABB overlap ≤ 1e-5 | in range, overlap 0 |
-| Outer AABB | (0.630, 0.615, 0.575) m ± 0.01 | (0.6300, 0.6150, 0.5750), zmin 0 |
-| Collider tris | ≤ 180 | 130 |
-| Export | written, size > 0 | 123436 / 123436 / 123416 bytes |
+| Outer AABB | (0.710, 0.419, 0.610) m ± 0.015 | (0.7100, 0.4185, 0.6100), zmin 0 |
+| Collider tris | ≤ 240 | 198 |
+| Export | written, size > 0 | 89316 / 89316 / 89312 bytes |
+
+### Hygiene
+
+Recomputed from the generated mesh, not asserted about the script.
+
+| Axis | Declared | Measured (all three) |
+| --- | --- | --- |
+| Non-manifold edges | 0 | 0 |
+| Loose verts / edges | 0 / 0 | 0 / 0 |
+| Doubles merged at 1e-5 | 0 | 0 |
+| Zero-area faces | 0 | 0 |
+| N-gons | 0 | 0 |
+| Coplanar disjoint face pairs | 0 | 0 |
+| Grounded: `zmin` | within 1e-4 of 0 | 0.0000 |
+| Named supports: 4 shoes | each `zmin` ≤ 1e-3 | 4, shoe_z 0.00000 |
+| Stone size | 0.500 m dia × 0.095 m thick ± 0.02 / ± 0.015 | 0.5000 × 0.0950 |
+
+### Joint fit and seat
+
+| Axis | Declared | Measured (all three) |
+| --- | --- | --- |
+| Crank-axle gap | ≤ 0.008 m | 0.00418 |
+| Shoe-wood BVH gap | ≤ 0.008 m (overlap is 0) | 0.00000 |
+| Trough-sill per-side gap | ≤ 0.008 m (overlap is 0) | 0.00000 |
+| Stone dip into trough | 0.015–0.045 m | 0.02570 |
+| Trough floor zmin | ≥ 0.040 m | 0.05800 |
 
 DECIMATE COLLAPSE triangle counts are **not** identical across series —
-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
-20 B on 5.2.1 (glTF serializer), not a gated axis.
+5.2.1 is leaner 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 4 B on 5.2.1 (glTF serializer), not a gated axis.
+
+### Falsifiers
 
-`--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.
+Each violates one named budget. All nine were run on 4.5.11, 5.1.2 and
+5.2.1 and returned the same code on each.
+
+| Flag | Budget violated | Exit |
+| --- | --- | --- |
+| `--skip-decimate` | LOD1 ratio band | 9 |
+| `--stray-vert` | loose vertex count is 0 | 15 |
+| `--lift-z` | bounding box `zmin` is 0 | 16 |
+| `--short-legs` | named shoe supports at Z=0 | 16 |
+| `--float-crank` | crank-axle gap | 17 |
+| `--float-legs` | shoe-wood join | 17 |
+| `--no-dip` | stone dip band | 18 |
+| `--narrow-trough` | trough-sill seat | 18 |
 
 ## Run
 
 ```bash
 blender --background --python grindstone.py --
 blender --background --python grindstone.py -- --skip-decimate
+blender --background --python grindstone.py -- --stray-vert
+blender --background --python grindstone.py -- --lift-z
+blender --background --python grindstone.py -- --short-legs
+blender --background --python grindstone.py -- --float-crank
+blender --background --python grindstone.py -- --float-legs
+blender --background --python grindstone.py -- --no-dip
+blender --background --python grindstone.py -- --narrow-trough
 blender --background --python grindstone.py -- --output grindstone.png
 ```
 
-Smoke does not pass `--output` or `--skip-decimate`.
+Smoke passes no flags.
 
 ## Exit codes
 
 File-local. `9` is a valid check code. `10` is reserved for
-`gallery_framing.check_framing` on the `--output` path.
+`gallery_framing.check_framing` on the `--output` path. `15`–`19` are the
+hygiene and joint-fit family.
 
 | Code | Meaning |
 | --- | --- |
@@ -61,7 +113,7 @@ File-local. `9` is a valid check code. `10` is reserved for
 | 2 | argparse / usage |
 | 3 | Mesh did not build / no UV layer |
 | 4 | Base triangle count outside range |
-| 5 | Material count ≠ 3 distinct slots, or wood/stone/metal faces missing |
+| 5 | Material count ≠ 3 distinct slots, or a face-count floor missed |
 | 6 | UVs outside 0..1 |
 | 7 | UV AABB overlap above tolerance |
 | 8 | World AABB off declared outer size |
@@ -71,3 +123,8 @@ File-local. `9` is a valid check code. `10` is reserved for
 | 12 | Bake did not finish or image has no data |
 | 13 | Export file missing or empty |
 | 14 | `--output` produced no file |
+| 15 | Mesh hygiene: loose, non-manifold, zero-area, doubles, n-gons, z-fight |
+| 16 | Not grounded: bounding box `zmin` off 0, or a named shoe floats |
+| 17 | Joint fit: crank-axle gap, or shoe-wood join |
+| 18 | Seat: trough-sill gap, stone dip band, or trough sitting on the dirt |
+| 19 | Stone diameter or thickness off the stated real-world size |