fix(examples): restage swatch-grid as a tiered material library with a glowing emissive (#259)

The gallery's first card rendered its emissive swatch as a flat, clipped
orange disk: a bare Emission at strength 1.4 clips the red channel across
the whole face under the Standard view transform, which Layer 1 forbids.
The rest of the card was six bare spheres against a wall, which read as
generic at thumbnail size.

The same asserted ShaderNodeEmission now owns the camera-facing face at
strength 0.95 (below clipping) and hands over to a dark dielectric shell
at the silhouette through a Layer Weight facing ramp, so the globe has a
limb; a shadowless point at its center throws its glow onto its own
collar, plinth and the floor. The spheres sit in gunmetal collars on
bevelled graphite plinths in two tiers on the default stage with a 50 mm
tracked camera.

verify_png now samples each swatch at its camera-projected center instead
of the center of an image third, so the six-region check follows the
layout. Every asserted material, the --same-base falsifier and the
engine-id witness are unchanged.

Signed-off-by: TMHSDigital <154358121+TMHSDigital@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: TMHSDigital

README.md

@@ -232,7 +232,7 @@ or expand a category below.
 <table>
 <tr>
 <td width="46%" valign="middle">
-<a href="examples/swatch-grid/"><img src="examples/swatch-grid/preview.webp" alt="Swatch grid: a three-by-two grid of shaded spheres - polished gold and brushed copper metals, red and blue plastics, an emissive orange, and a matte white - against a dark studio backdrop, rendered with EEVEE" /></a>
+<a href="examples/swatch-grid/"><img src="examples/swatch-grid/preview.webp" alt="Swatch grid: a tiered material library in a dark studio - six spheres seated in chrome collars on graphite plinths, mirror gold, brushed copper and red plastic on tall plinths behind blue plastic, a glowing orange emissive globe and matte white in front, rendered with EEVEE" /></a>
 </td>
 <td valign="middle">
 

docs/gallery/assets/swatch-grid-hero.webp

@@ -343,7 +343,7 @@ <h1>Examples and Showcase</h1>
     <div class="grid" id="grid">
       <article class="card" data-tags="materials rendering">
         <a class="card-media" href="swatch-grid/" tabindex="-1" aria-hidden="true">
-          <img src="assets/swatch-grid-hero.webp" alt="Six material spheres in two rows against a dark backdrop: mirror gold, brushed copper, red, blue, flat orange emission and white." loading="lazy" decoding="async" />
+          <img src="assets/swatch-grid-hero.webp" alt="Six material spheres on graphite plinths in two tiers: mirror gold, brushed copper and red behind; blue, a glowing orange emissive globe and matte white in front." loading="lazy" decoding="async" />
         </a>
         <div class="card-body">
           <h2><a href="swatch-grid/">swatch-grid</a></h2>

docs/gallery/contact-sheets/swatch-grid-contact-sheet.webp

@@ -9,7 +9,7 @@
       "name": "swatch-grid",
       "dir": "examples/swatch-grid",
       "teaches": "Procedural Principled materials — metal and dielectric, the emission pattern, and the cross-version set_specular shim.",
-      "alt": "Six material spheres in two rows against a dark backdrop: mirror gold, brushed copper, red, blue, flat orange emission and white.",
+      "alt": "Six material spheres on graphite plinths in two tiers: mirror gold, brushed copper and red behind; blue, a glowing orange emissive globe and matte white in front.",
       "witnessesFix": "EEVEE engine-id mapping: BLENDER_EEVEE on 5.x, BLENDER_EEVEE_NEXT on 4.2–4.5.",
       "hero": "docs/gallery/assets/swatch-grid-hero.webp",
       "preview": "examples/swatch-grid/preview.webp",

docs/gallery/index.html

@@ -1,13 +1,14 @@
 # Swatch Grid
 
-A runnable example that renders a 3×2 grid of spheres — one material per cell — to a single
-PNG. It demonstrates the [`procedural-materials-and-shaders`](../../skills/procedural-materials-and-shaders/SKILL.md)
+A runnable example that renders a tiered 3×2 material library — one sphere per material, each
+seated in a chrome collar on a graphite plinth — to a single PNG. It demonstrates the [`procedural-materials-and-shaders`](../../skills/procedural-materials-and-shaders/SKILL.md)
 patterns end to end:
 
 - **Principled BSDF** metals (gold, copper: high metallic, low roughness) and dielectrics
   (red/blue plastic, white rough), configured with **string socket lookups** and **4-tuple
   colors**.
-- The **emission** pattern (an emissive orange swatch).
+- The **emission** pattern (an emissive orange swatch, its `ShaderNodeEmission` core mixed
+  toward a dark dielectric shell at the silhouette so it reads as a glowing globe).
 - The cross-version **`set_specular` shim** (`Specular` → `Specular IOR Level`, renamed in
   Blender 4.0).
 
@@ -36,14 +37,31 @@ blender --background --python swatch_grid.py -- --output swatch.png --engine cyc
 
 ## Staging
 
-The backdrop stands 0.16 behind the spheres, so each casts a soft contact
-shadow. It used to stand 1.58 behind them, and the grid floated. The world is
-a reflection-only sky: glossy rays see a warm overhead gradient above a dark
-horizon, and camera and diffuse rays see the dark stage. The mirror-finish
-gold otherwise reflected the near-black world and rendered as a black ball
-with two light-card glints. Sphere positions, materials, the camera and the
-six-region pixel check are unchanged; `verify_png` still reads six distinct
-regions on 4.5.11, 5.1.2 and 5.2.1.
+The swatches stand as a tiered material library on the default stage (floor,
+wall at y = 9, warm key, cool fill and rim, warm wedge pooling on the floor
+behind the display). Each sphere sits in a gunmetal collar on a bevelled
+graphite plinth; the back row stands on tall plinths so every sphere clears
+the one in front of it. A 50 mm camera looks down on the display with a
+`TRACK_TO` aim, which keeps the floor/wall seam above the back row.
+
+The emissive swatch used to be a bare `Emission` at strength 1.4: under the
+Standard view transform its red channel clipped across the whole face and it
+rendered as a flat orange disk. Now the same `ShaderNodeEmission` (color and
+strength asserted) owns the face toward the camera at strength 0.95, below
+clipping, and a `Layer Weight` facing ramp hands it over to a dark dielectric
+shell at the silhouette, so the globe has a limb. A shadowless warm point
+light at its center stands in for the glow it throws on its own collar,
+plinth and the floor; the shell is lit from inside only on back faces, so the
+ball itself still shows only the asserted emission.
+
+The world is a reflection-only sky: glossy rays see a warm overhead gradient
+above a dark horizon, and camera and diffuse rays see the dark stage. The
+mirror-finish gold otherwise reflects the near-black world as a black ball.
+
+`verify_png` samples each swatch where the camera sees it: the sphere center
+is projected through the render camera (`world_to_camera_view`) rather than
+assumed to sit at the center of a third of the frame, so the six-region check
+follows the layout.
 
 ## Exit codes