fix(showcase): street-lantern and water-trough visual quality pass

docs/gallery/grindstone/index.html

@@ -1022,7 +1022,7 @@ <h2>Source</h2>
     <span class="k">for</span> p <span class="k">in</span> me.polygons:
         <span class="k">if</span> all(i <span class="k">in</span> member <span class="k">for</span> i <span class="k">in</span> p.vertices):
             <span class="k">return</span> p.material_index
-    <span class="k">return</span> -<span class="n">1</span>
+    <span class="k">return</span> <span class="k">None</span>
 
 
 <span class="k">def</span> support_audit(me):

docs/gallery/index.html

@@ -947,7 +947,7 @@ <h2><a href="market-stall/">market-stall</a></h2>
         <div class="card-body">
           <h2><a href="street-lantern/">street-lantern</a></h2>
           <p class="teaches">A procedural hanging street lantern 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: 3520 tris, three materials with 24 glass and 94 brass faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.403×0.892×1.404 m, LOD ratios in band, convex collider 84 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.</p>
+          <p class="witnesses"><span class="tag">witnesses</span> Recomputed: 3338 tris, three materials with 1530 metal, 24 glass and 209 brass faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.300×0.786×1.287 m, zmin 0, hygiene 0, brace BVH gap 0, hanger-roof gap −1 mm, post 0.100×1.120 m plumb 0, LOD ratios in band (5.2 COLLAPSE 2 tris leaner on LOD2), convex collider 78 tris, non-empty glTF. --skip-decimate exits 9; --stray-vert 15; --lift-z 16; --float-brace 17; --sink-arm 18; --rake-post 19.</p>
           <a class="card-link" href="street-lantern/">View example <span aria-hidden="true">&rarr;</span></a>
         </div>
       </article>
@@ -1046,7 +1046,7 @@ <h2><a href="anvil/">anvil</a></h2>
         <div class="card-body">
           <h2><a href="water-trough/">water-trough</a></h2>
           <p class="teaches">A procedural watertight water trough 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: 2484 tris, three materials with 192 metal and 6 water faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.152×0.568×0.509 m, LOD ratios in band (5.2 COLLAPSE 8 tris leaner on LOD2), convex collider 32 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.</p>
+          <p class="witnesses"><span class="tag">witnesses</span> Recomputed: 3700 tris, three materials with 1674 wood, 156 metal and 29 water faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.093×0.552×0.504 m, zmin 0, four shoes planted, U end-cap rim span 5 mm, strap BVH gap 0, water-hull gap 2.6 mm, hull 1.045×0.466 m, LOD ratios in band, convex collider 64 tris, non-empty glTF. --skip-decimate exits 9; --stray-vert 15; --lift-z/--short-legs 16; --box-ends 17; --float-strap 18; --narrow-hull 19.</p>
           <a class="card-link" href="water-trough/">View example <span aria-hidden="true">&rarr;</span></a>
         </div>
       </article>

showcase/README.md

@@ -50,7 +50,13 @@ entry in `showcase/gallery.json`, and a rendered still.
   flat fan cap are coplanar and close-centred by construction, and
   counting those makes the budget unsatisfiable rather than meaningful.
   Multi-body props do **not** require Euler characteristic 2 — that is a
-  single-shell contract. Pairs of parts meant to touch assert a BVH
+  single-shell contract. Two boxes that share a coplanar face z-fight;
+  two that share a vertex weld into one shell. Seat a joint with a named
+  overlap or rebate computed from the host (a cage post into its rail, a
+  glass pane behind its muntin, a plinth step into its base) rather than
+  hoping the numbers happen not to coincide. A hang-station versus
+  arm-station split lets a contact falsifier move one member without
+  dragging the rest of the assembly. 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). A spanning board whose only vertices sit at
   the far ends will report a false gap to a mid-span knuckle; put a

showcase/gallery.json

@@ -69,7 +69,7 @@
       "name": "street-lantern",
       "dir": "showcase/street-lantern",
       "teaches": "A procedural hanging street lantern through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.",
-      "witnessesFix": "Recomputed: 3520 tris, three materials with 24 glass and 94 brass faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.403×0.892×1.404 m, LOD ratios in band, convex collider 84 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.",
+      "witnessesFix": "Recomputed: 3338 tris, three materials with 1530 metal, 24 glass and 209 brass faces, UVs in 0..1 with zero AABB overlap, outer AABB 0.300×0.786×1.287 m, zmin 0, hygiene 0, brace BVH gap 0, hanger-roof gap −1 mm, post 0.100×1.120 m plumb 0, LOD ratios in band (5.2 COLLAPSE 2 tris leaner on LOD2), convex collider 78 tris, non-empty glTF. --skip-decimate exits 9; --stray-vert 15; --lift-z 16; --float-brace 17; --sink-arm 18; --rake-post 19.",
       "hero": "docs/gallery/assets/street-lantern-hero.webp",
       "preview": "showcase/street-lantern/preview.webp",
       "tags": [
@@ -177,7 +177,7 @@
       "name": "water-trough",
       "dir": "showcase/water-trough",
       "teaches": "A procedural watertight water trough through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets rather than an API contract.",
-      "witnessesFix": "Recomputed: 2484 tris, three materials with 192 metal and 6 water faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.152×0.568×0.509 m, LOD ratios in band (5.2 COLLAPSE 8 tris leaner on LOD2), convex collider 32 tris, non-empty glTF. --skip-decimate exits 9 on the LOD1 ratio budget.",
+      "witnessesFix": "Recomputed: 3700 tris, three materials with 1674 wood, 156 metal and 29 water faces, UVs in 0..1 with zero AABB overlap, outer AABB 1.093×0.552×0.504 m, zmin 0, four shoes planted, U end-cap rim span 5 mm, strap BVH gap 0, water-hull gap 2.6 mm, hull 1.045×0.466 m, LOD ratios in band, convex collider 64 tris, non-empty glTF. --skip-decimate exits 9; --stray-vert 15; --lift-z/--short-legs 16; --box-ends 17; --float-strap 18; --narrow-hull 19.",
       "hero": "docs/gallery/assets/water-trough-hero.webp",
       "preview": "showcase/water-trough/preview.webp",
       "tags": [

showcase/street-lantern/README.md

@@ -2,9 +2,17 @@
 
 A showcase piece, not an example. Procedural hanging street lantern
 (stepped iron foot, tapered octagonal post, brass collars, braced arm,
-muntined cage with amber panes, pyramidal brass roof and finial) then
-the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake,
-LOD chain, convex collider, Unity glTF export.
+muntined cage with amber panes, square pyramidal brass roof and finial)
+then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal
+bake, LOD chain, convex collider, Unity glTF export.
+
+The arm axis, drop length, and roof stack are one closed-form chain: the
+roof peak stays below the arm, the hanger is the arm's far station, and
+the brace is an oriented box between a post-radius station and an arm
+station. The square pyramid is lofted on the cage axes, not a 4-gon cone.
+Cage posts and rails share a named overlap (`CAGE_JOINT`); glass sits
+behind the muntins by `PANE_REBATE`. Collars and the arm root evaluate
+`post_radius_at(z)`.
 
 It asserts **budget conformance** of the generated result. It does not
 witness an API contract. "It rendered without error" is not a check.
@@ -14,6 +22,12 @@ witness an API contract. "It rendered without error" is not a check.
 `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).
+Hygiene combinatorics match `examples/mesh-hygiene-audit` (copied, not
+imported).
+
+Intended size: 0.30 m square foot, 1.12 m octagonal post (0.10 m across
+at the base), 0.50 m arm, 0.24 × 0.30 m cage; outer AABB
+0.300 × 0.786 × 1.287 m.
 
 ## Budgets
 
@@ -22,38 +36,87 @@ materials, UVs, evaluated LOD, collider, or export file.
 
 | Axis | Declared | Measured (4.5.11 / 5.1.2 / 5.2.1) |
 | --- | --- | --- |
-| Base triangles | 3400–3650 | 3520 / 3520 / 3520 |
-| LOD1 ratio | 0.32–0.62 of base | 0.5000 / 0.5000 / 0.5000 |
-| LOD2 ratio | 0.10–0.35 of base | 0.2199 / 0.2199 / 0.2199 |
-| Materials | exactly 3 distinct, ≥8 glass faces, ≥8 brass faces | 3 slots, 24 glass, 94 brass |
+| Base triangles | 3000–3800 | 3338 / 3338 / 3338 |
+| LOD1 ratio | 0.32–0.62 of base | 0.4997 / 0.4997 / 0.4997 |
+| LOD2 ratio | 0.10–0.35 of base | 0.2199 / 0.2199 / 0.2193 |
+| Materials | exactly 3 distinct; ≥200 metal, ≥8 glass, ≥24 brass | 3 slots; 1530 / 24 / 209 |
 | UVs | in `0..1`, AABB overlap ≤ 1e-5 | in range, overlap 0 |
-| Outer AABB | (0.403, 0.892, 1.404) m ± 0.01 | (0.4032, 0.8916, 1.4041), zmin 0 |
-| Collider tris | ≤ 110 | 84 |
-| Export | written, size > 0 | 254552 / 254552 / 254536 bytes |
+| Outer AABB | (0.300, 0.786, 1.287) m ± 0.01 | (0.3000, 0.7860, 1.2874), zmin 0 |
+| Collider tris | ≤ 120 | 78 |
+| Export | written, size > 0 | 250980 / 250980 / 250964 bytes |
+
+Base triangles dropped from **3520 to 3338** in the quality pass: the
+open 4-gon cone roof became a closed square pyramid, cage crossings
+stopped sharing vertices, and a pane rebate replaced coplanar glass.
+
+DECIMATE COLLAPSE triangle counts are **not** identical across series —
+5.2.1 is 2 tris 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 16 B on 5.2.1 (glTF serializer), not a gated axis.
+
+### 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 |
+| Post plan | 0.100 m across × 1.120 m high ± (0.02, 0.04) | 0.1000 × 1.1200 |
+| Post plumb (top vs bottom XY) | ≤ 0.008 m | 0.00000 |
+
+### Joint fit and seat
+
+| Axis | Declared | Measured (all three) |
+| --- | --- | --- |
+| Brace-to-arm BVH gap | ≤ 0.006 m | 0.00000 |
+| Arm underside vs roof peak | ≥ 0.008 m clearance | 0.05300 |
+| Hanger-to-roof BVH gap | ≤ 0.004 m | −0.00100 |
 
-DECIMATE COLLAPSE triangle counts are **not** guaranteed identical across
-series — the gate is a ratio band, not an exact count. This mesh happened
-to match on 4.5.11 / 5.1.2 / 5.2.1. Bake pixels are stochastic; the gate
-is `has_data` plus operator `FINISHED`, not byte-identity. Construction
-uses no RNG. glTF byte size differs by a few bytes across series.
+### Falsifiers
+
+Each violates one named budget. All six 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 |
+| `--float-brace` | brace-to-arm BVH gap | 17 |
+| `--sink-arm` | arm-over-roof clearance | 18 |
+| `--rake-post` | post plumb | 19 |
 
-`--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.
+`--sink-arm` lowers only the arm. Hang-station `hang_z` stays at post
+top so the cage does not follow, which is what lets the clearance budget
+fire.
 
 ## Run
 
 ```bash
 blender --background --python street_lantern.py --
 blender --background --python street_lantern.py -- --skip-decimate
+blender --background --python street_lantern.py -- --stray-vert
+blender --background --python street_lantern.py -- --lift-z
+blender --background --python street_lantern.py -- --float-brace
+blender --background --python street_lantern.py -- --sink-arm
+blender --background --python street_lantern.py -- --rake-post
 blender --background --python street_lantern.py -- --output lantern.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 |
 | --- | --- |
@@ -62,7 +125,7 @@ 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 glass/brass 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 |
@@ -72,3 +135,8 @@ 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 |
+| 17 | Joint fit: brace-to-arm gap (`--float-brace`) |
+| 18 | Seat: arm-roof clearance or hanger-roof gap (`--sink-arm`) |
+| 19 | Post plumb or post size off the stated real-world size (`--rake-post`) |