feat: add gp-lineart-contour example (#100)

Witness Grease Pencil LINEART modifier contours via the depsgraph, the
source_object and edge-flag failure modes, and the thickness→radius trap
across 4.5 LTS and 5.1.

Signed-off-by: fOuttaMyPaint <TMhospitalitystrategies@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: TMHSDigital

.cursor-plugin/plugin.json

@@ -73,6 +73,7 @@
     "examples/gltf-skin-roundtrip",
     "examples/gn-instance-grid",
     "examples/gn-sdf-remesh",
+    "examples/gp-lineart-contour",
     "examples/grease-pencil-rosette",
     "examples/image-pixels-testcard",
     "examples/light-link-studio",

.github/workflows/blender-smoke.yml

@@ -287,6 +287,17 @@ jobs:
           xvfb-run -a "$BLENDER" --background \
             --python examples/grease-pencil-rosette/grease_pencil_rosette.py --
 
+      - name: Shipped example - gp line art contour (LINEART modifier + thickness trap)
+        run: |
+          set -euo pipefail
+          # Check only (no render): GPv3 object + LINEART modifier; asserts
+          # source_object is load-bearing (clear → 0 strokes), contour+crease
+          # off → 0, restore recovers silhouette strokes, and thickness is
+          # 4.5-only (AttributeError on 5.1; portable path is radius).
+          # Exits non-zero on failure.
+          xvfb-run -a "$BLENDER" --background \
+            --python examples/gp-lineart-contour/gp_lineart_contour.py --
+
       - name: Shipped example - armature bend (edit_bones + LBS closed form)
         run: |
           set -euo pipefail

README.md

@@ -18,7 +18,7 @@
 </p>
 
 <p align="center">
-  <strong>12 skills</strong> &nbsp;&bull;&nbsp; <strong>6 rules</strong> &nbsp;&bull;&nbsp; <strong>2 templates</strong> &nbsp;&bull;&nbsp; <strong>17 snippets</strong> &nbsp;&bull;&nbsp; <strong>33 examples</strong>
+  <strong>12 skills</strong> &nbsp;&bull;&nbsp; <strong>6 rules</strong> &nbsp;&bull;&nbsp; <strong>2 templates</strong> &nbsp;&bull;&nbsp; <strong>17 snippets</strong> &nbsp;&bull;&nbsp; <strong>34 examples</strong>
 </p>
 
 <p align="center">
@@ -36,7 +36,7 @@
 
 ## Overview
 
-This repository ships **12 skills, 6 rules, 2 templates, 17 snippets, and 33 runnable examples** for Blender Python development targeting Blender 5.1 (current stable) with Blender 4.5 LTS fallback support.
+This repository ships **12 skills, 6 rules, 2 templates, 17 snippets, and 34 runnable examples** for Blender Python development targeting Blender 5.1 (current stable) with Blender 4.5 LTS fallback support.
 
 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.
 
@@ -482,7 +482,7 @@ and every orbit lands on its closed form.
 </details>
 
 <details>
-<summary><strong>Context &amp; Grease Pencil</strong> — 2 examples</summary>
+<summary><strong>Context &amp; Grease Pencil</strong> — 3 examples</summary>
 
 <table>
 <tr>
@@ -514,6 +514,22 @@ while `grease_pencils` is still legacy; on 5.x legacy is gone and GPv3 owns the
 name. Point writes lazily materialize attribute layers, and every position
 round-trips through the raw `POINT` buffer.
 
+</td>
+</tr>
+<tr>
+<td width="46%" valign="middle">
+<a href="examples/gp-lineart-contour/"><img src="examples/gp-lineart-contour/preview.webp" alt="GP Line Art contour: a faceted teal crystal on a dark studio floor outlined in neon cyan Grease Pencil Line Art strokes, proving modifiers.new LINEART with source_object silhouette evaluation" /></a>
+</td>
+<td valign="middle">
+
+### [gp-lineart-contour](examples/gp-lineart-contour/)
+
+Grease Pencil `LINEART` modifier contours via the depsgraph — not Freestyle and
+not hand-drawn strokes. `source_object` is load-bearing (clear → 0 strokes);
+contour+crease off → 0; restore recovers **10** strokes / **34** points on both
+binaries. Stroke width: `thickness` exists on 4.5, `AttributeError` on 5.1 —
+portable path is `radius`.
+
 </td>
 </tr>
 </table>

ROADMAP.md

@@ -115,7 +115,7 @@ Not committed; target list for the next content version. (v0.3.0 shipped the smo
 - ~~Collision compound witness~~ **SHIPPED** as `examples/collision-hull-proxy/` — game-prop collision as a compound of convex pieces, each a `bmesh.ops.convex_hull` of a coarse `sec(π/n)`-inflated cage (containment 4.4e-08, watertight, positive signed volume, Euler 2, per-piece 255-face budget: body 70, caps 60×3, compound 250); a hull of the dense render mesh measures 380 faces — over budget — which is why pipelines hull cages; proud details cost cage rows, concave grooves are free; byte-identical on 4.5.11 and 5.1.2
 - ~~Custom-normals / shade-by-angle witness~~ **SHIPPED** as `examples/custom-normals-shade/` — the post-4.1 shading contract: `use_auto_smooth`/`use_custom_normals`/`calc_normals` are AttributeError on BOTH 4.5.11 and 5.1.2; `set_sharp_from_angle` sharp sets match an independent dihedral recompute exactly (188/388 edges, 3 meshes); evaluated normal welds/splits exact (0.0 dev); custom split normals survive depsgraph evaluation within int16 quantization (1.407e-04, not float-exact); **divergence**: the legacy `shade_auto_smooth` operator CANCELS headless on 4.5 ("Asset loading is unfinished", mesh untouched, no exception) while 5.1 FINISHES with the Smooth-by-Angle NODES modifier — the data API is the portable path
 - ~~Sky Texture / sun_elevation witness~~ **SHIPPED** as `examples/sky-texture-sun-elevation/` — World `ShaderNodeTexSky` → Background; `sky_type` is `NISHITA` on 4.5 and `MULTIPLE_SCATTERING` on 5.1 (`NISHITA` gone); `dust_density` is 4.5-only (`aerosol_density` on 5.1); zenith EXR rise 8°→55° measured **2.25x** (5.1.2) / **1.50x** (4.5.11), gate ≥ 1.25; dual-elevation gallery diptych
-- Grease Pencil Line Art contour witness: empty GPv3 object + `modifiers.new(..., "LINEART")`; `thickness` on 4.5 vs `radius` on 5.1; evaluated contour stroke counts for a known source mesh
+- ~~Grease Pencil Line Art contour witness~~ **SHIPPED** as `examples/gp-lineart-contour/` — GPv3 + `modifiers.new(..., "LINEART")`; `source_object` clear → 0 strokes; contour+crease off → 0; restore recovers **10** strokes / **34** points on 4.5.11 and 5.1.2; `thickness` is 4.5-only (`AttributeError` on 5.1; portable `radius`)
 - Camera DOF + focus_distance witness: `cam.dof.use_dof`, focus plane vs defocus variance on high-freq cards (Stage deviation — depth needs background content)
 - Volumetric scatter optical-depth witness: Volume Scatter density → Beer–Lambert transmittance along a known path (Cycles; Stage deviation)
 - Freestyle SVG / line-set witness: Freestyle line set on a silhouette (full render pass; prefer Line Art first)