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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>attribute-domain-shear — Examples — Blender Developer Tools</title>
<meta name="description" content="POINT vs CORNER color-attribute domains on a shared-vertex pinwheel: CORNER stays exact per face while a naive per-wedge POINT loop shears to the last write at the hub. Crisp petals versus a smeared swirl in one frame; the measured shear equals the palette closed form." />
<link rel="canonical" href="https://tmhsdigital.github.io/Blender-Developer-Tools/gallery/attribute-domain-shear/" />
<link rel="icon" href="../../assets/favicon.svg" type="image/svg+xml" />
<meta name="theme-color" content="#1a1b1e" />
<meta name="color-scheme" content="dark" />
<meta property="og:type" content="website" />
<meta property="og:title" content="attribute-domain-shear — Examples — Blender Developer Tools" />
<meta property="og:description" content="POINT vs CORNER color-attribute domains on a shared-vertex pinwheel: CORNER stays exact per face while a naive per-wedge POINT loop shears to the last write at the hub. Crisp petals versus a smeared swirl in one frame; the measured shear equals the palette closed form." />
<meta property="og:url" content="https://tmhsdigital.github.io/Blender-Developer-Tools/gallery/attribute-domain-shear/" />
<meta property="og:image" content="https://tmhsdigital.github.io/Blender-Developer-Tools/gallery/assets/attribute-domain-shear-hero.webp" />
<meta property="og:image:width" content="1280" />
<meta property="og:image:height" content="720" />
<meta property="og:image:alt" content="attribute-domain-shear: the example's own headless render" />
<meta property="og:site_name" content="Blender Developer Tools" />
<meta name="twitter:card" content="summary_large_image" />
<meta name="twitter:title" content="attribute-domain-shear — Examples — Blender Developer Tools" />
<meta name="twitter:description" content="POINT vs CORNER color-attribute domains on a shared-vertex pinwheel: CORNER stays exact per face while a naive per-wedge POINT loop shears to the last write at the hub. Crisp petals versus a smeared swirl in one frame; the measured shear equals the palette closed form." />
<meta name="twitter:image" content="https://tmhsdigital.github.io/Blender-Developer-Tools/gallery/assets/attribute-domain-shear-hero.webp" />
<meta name="twitter:image:alt" content="attribute-domain-shear: the example's own headless render" />
<style>
/* fonts are deployed by the landing build (docs/fonts/) */
@font-face { font-family: 'Barlow Condensed'; font-weight: 600; font-display: swap;
src: url('../../fonts/barlow-condensed-600.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-weight: 400; font-display: swap;
src: url('../../fonts/inter-regular.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-weight: 500; font-display: swap;
src: url('../../fonts/inter-medium.woff2') format('woff2'); }
@font-face { font-family: 'JetBrains Mono'; font-weight: 400; font-display: swap;
src: url('../../fonts/jetbrains-mono-regular.woff2') format('woff2'); }
/* Blender-viewport system, shared with the landing page. Dark only. */
:root {
color-scheme: dark;
--bg: #1a1b1e; --surface: #222327; --surface-2: #2a2b30; --bg2: #131417;
--border: #3a3b40; --text: #e8e9eb; --text-dim: #9698a0;
--select: #ff8c19; --ok: #6dc96d;
--radius: 4px; --radius-lg: 6px; --maxw: 1080px;
--font-display: 'Barlow Condensed', 'Arial Narrow', sans-serif;
--font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
--font-mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
--code-k: #ff7b72; --code-s: #a5d6ff; --code-c: #9698a0; --code-n: #79c0ff;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { font-family: var(--font-sans); background: var(--bg); color: var(--text);
line-height: 1.6; min-height: 100vh; -webkit-font-smoothing: antialiased; }
a { color: var(--select); text-decoration: none; }
a:hover { text-decoration: underline; }
:focus-visible { outline: 2px solid var(--select); outline-offset: 2px; border-radius: 3px; }
::selection { background: color-mix(in srgb, var(--select) 40%, transparent); }
.skip { position: absolute; left: -999px; top: 0; background: var(--select); color: #1a1b1e;
padding: 0.5rem 1rem; border-radius: var(--radius); z-index: 10; font-weight: 500; }
.skip:focus { left: 0.5rem; top: 0.5rem; }
.hud { font-family: var(--font-mono); font-size: 0.6875rem; letter-spacing: 0.04em;
color: var(--text-dim); text-transform: uppercase; }
.topbar { position: sticky; top: 0; z-index: 5; display: flex; align-items: center;
justify-content: space-between; gap: 1rem; padding: 0 1.25rem; height: 46px;
background: color-mix(in srgb, var(--surface) 92%, transparent);
backdrop-filter: blur(10px); border-bottom: 1px solid var(--border); }
.topbar .back { color: var(--text-dim); font-size: 0.8125rem; font-weight: 500; }
.topbar .back:hover { color: var(--select); text-decoration: none; }
.topbar-right { display: flex; align-items: center; gap: 0.85rem; }
.topbar-right .ghlink { color: var(--text-dim); font-size: 0.8125rem; font-weight: 500; }
.topbar-right .ghlink:hover { color: var(--select); text-decoration: none; }
header.hero { max-width: var(--maxw); margin: 0 auto; padding: 2.75rem 1.25rem 1.25rem; }
header.hero h1 { font-family: var(--font-display); font-weight: 600; text-transform: uppercase;
font-size: clamp(2.2rem, 5vw, 3.4rem); letter-spacing: 0.005em; line-height: 0.98; }
header.hero p { color: var(--text-dim); max-width: 62ch; margin-top: 0.7rem; font-size: 1rem; }
/* ---- index: sticky controls (search, density toggle, tag chips) ---- */
.controls { position: sticky; top: 46px; z-index: 4;
background: color-mix(in srgb, var(--bg) 94%, transparent);
backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
border-bottom: 1px solid var(--border); }
.controls-inner { max-width: var(--maxw); margin: 0 auto; padding: 0.55rem 1.25rem 0.6rem;
display: flex; flex-direction: column; gap: 0.5rem; }
.controls-row { display: flex; align-items: center; gap: 0.6rem; flex-wrap: wrap; }
.searchwrap { position: relative; flex: 1 1 240px; min-width: 150px; }
.searchwrap input { width: 100%; background: var(--surface-2); border: 1px solid var(--border);
color: var(--text); border-radius: var(--radius); padding: 0.34rem 1.9rem 0.34rem 0.7rem;
font-family: var(--font-sans); font-size: 0.85rem; line-height: 1.4; }
.searchwrap input:focus { border-color: var(--select); outline: none; }
.searchwrap input::placeholder { color: var(--text-dim); }
.searchwrap input::-webkit-search-cancel-button { -webkit-appearance: none; appearance: none; }
.q-clear { position: absolute; right: 0.2rem; top: 50%; transform: translateY(-50%);
background: none; border: none; color: var(--text-dim); font-size: 1.05rem; line-height: 1;
cursor: pointer; padding: 0.25rem 0.45rem; border-radius: 3px; }
.q-clear:hover { color: var(--select); }
.count { font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.04em;
text-transform: uppercase; color: var(--text-dim); white-space: nowrap; }
.density { display: flex; border: 1px solid var(--border); border-radius: var(--radius);
overflow: hidden; }
.density-btn { background: var(--surface-2); border: none; color: var(--text-dim); cursor: pointer;
font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.04em;
text-transform: uppercase; padding: 0.36rem 0.7rem; transition: color 0.15s, background 0.15s; }
.density-btn + .density-btn { border-left: 1px solid var(--border); }
.density-btn:hover { color: var(--select); }
.density-btn.active { background: var(--select); color: #1a1b1e; }
.tags-toggle { display: none; background: var(--surface-2); border: 1px solid var(--border);
color: var(--text-dim); border-radius: 3px; padding: 0.3rem 0.7rem; cursor: pointer;
font-family: var(--font-mono); font-size: 0.7rem; letter-spacing: 0.04em; text-transform: uppercase; }
.tags-toggle:hover, .tags-toggle.has-active { color: var(--select); border-color: var(--select); }
/* Tag chips wrap by default (no-JS safe). With JS the row becomes a scroll
strip on wide viewports and collapses behind the Tags toggle on narrow
ones, so the sticky bar never eats the mobile viewport. */
.chips { display: flex; flex-wrap: wrap; gap: 0.4rem; }
html.js .chips { flex-wrap: nowrap; overflow-x: auto; padding-bottom: 0.25rem;
scrollbar-width: thin; scrollbar-color: var(--border) transparent; }
html.js .chips::-webkit-scrollbar { height: 5px; }
html.js .chips::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
.chip { background: var(--surface-2); border: 1px solid var(--border); color: var(--text-dim);
border-radius: 3px; padding: 0.22rem 0.7rem; font-size: 0.72rem; font-weight: 400;
font-family: var(--font-mono); cursor: pointer; white-space: nowrap; flex: 0 0 auto;
transition: color 0.15s, border-color 0.15s; }
.chip:hover { color: var(--select); border-color: var(--select); }
.chip.active { color: #1a1b1e; background: var(--select); border-color: var(--select); }
@media (max-width: 719px) {
html.js .tags-toggle { display: inline-block; }
html.js .chips { display: none; }
html.js .chips.open { display: flex; flex-wrap: wrap; overflow-y: auto; max-height: 40vh; }
}
/* Compact density: hero + name + one-line teaser. The description and
WITNESSES text stay in the DOM (searchable, screen-reader reachable,
present with JS disabled when the class is never applied) but are
visually collapsed. Applied only by JS via the density-compact class. */
html.density-compact .grid { gap: 1rem; }
html.density-compact .card-body { padding: 0.65rem 0.9rem 0.7rem; }
html.density-compact .card-body h2 { font-size: 0.88rem; margin-bottom: 0.15rem; }
html.density-compact .teaches { font-size: 0.8rem; color: var(--text-dim); margin-bottom: 0;
white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
html.density-compact .witnesses { position: absolute; width: 1px; height: 1px; margin: -1px;
padding: 0; overflow: hidden; clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap; }
html.density-compact .card-link { display: none; }
.noresults { color: var(--text-dim); text-align: center; padding: 3rem 1rem; font-size: 0.95rem; }
.noresults .chip { margin-left: 0.6rem; }
.to-top { position: fixed; right: 1.25rem; bottom: 1.25rem; z-index: 6; cursor: pointer;
background: var(--surface-2); border: 1px solid var(--border); color: var(--text-dim);
border-radius: var(--radius); padding: 0.45rem 0.75rem;
font-family: var(--font-mono); font-size: 0.7rem; letter-spacing: 0.04em;
text-transform: uppercase; opacity: 0; visibility: hidden;
transition: opacity 0.2s, visibility 0.2s, color 0.15s, border-color 0.15s; }
.to-top.show { opacity: 1; visibility: visible; }
.to-top:hover { color: var(--select); border-color: var(--select); }
main { max-width: var(--maxw); margin: 0 auto; padding: 1rem 1.25rem 2rem; }
.grid { display: grid; grid-template-columns: 1fr; gap: 1.5rem; align-items: stretch; }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
overflow: hidden; display: flex; flex-direction: column;
outline: 2px solid transparent; outline-offset: -1px;
transition: outline-color 0.12s ease, border-color 0.12s ease; }
.card:hover { border-color: var(--select); outline-color: var(--select); }
.card.hidden { display: none; }
.card-media { display: block; background: var(--bg2); line-height: 0; }
.card-media img { display: block; width: 100%; aspect-ratio: 16 / 9; object-fit: cover; }
.card-body { padding: 1.15rem 1.4rem 1.45rem; display: flex; flex-direction: column; flex: 1 1 auto; }
.card-body h2 { font-family: var(--font-mono); font-size: 1rem; font-weight: 400; margin-bottom: 0.5rem; }
.card-body h2 a { color: var(--text); }
.card-body h2 a:hover { color: var(--select); text-decoration: none; }
.teaches { color: var(--text); margin-bottom: 0.7rem; font-size: 0.92rem; }
.witnesses { color: var(--text-dim); font-size: 0.85rem; margin-bottom: 1rem; }
.tag { display: inline-block; font-family: var(--font-mono); font-size: 0.62rem; text-transform: uppercase;
letter-spacing: 0.06em; color: var(--select); border: 1px solid color-mix(in srgb, var(--select) 55%, transparent);
border-radius: 3px; padding: 0.08rem 0.5rem; margin-right: 0.4rem; vertical-align: 1px; }
.card-link { font-weight: 600; font-size: 0.95rem; margin-top: auto; }
/* ---- detail page ---- */
.detail-hero { border: 1px solid var(--border); border-radius: var(--radius-lg); overflow: hidden;
background: var(--bg2); padding: 0; display: block; width: 100%; cursor: zoom-in; line-height: 0; }
.detail-hero img { display: block; width: 100%; aspect-ratio: 16 / 9; object-fit: cover; }
.zoom-hint { color: var(--text-dim); font-size: 0.78rem; margin-top: 0.4rem; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0);
white-space: nowrap; }
.callout { border: 1px solid color-mix(in srgb, var(--select) 45%, var(--border));
border-left: 3px solid var(--select); border-radius: var(--radius);
background: color-mix(in srgb, var(--select) 7%, var(--surface));
padding: 0.85rem 1.1rem; margin: 1.5rem 0; font-size: 0.95rem; }
.runline { display: flex; align-items: stretch; gap: 0.5rem; margin: 1.5rem 0; }
.runline pre { flex: 1 1 auto; background: var(--surface-2); border: 1px solid var(--border);
border-radius: var(--radius); padding: 0.7rem 0.9rem; overflow-x: auto;
font-family: var(--font-mono); font-size: 0.83rem; line-height: 1.5; }
.copy-btn { flex: 0 0 auto; background: var(--surface-2); border: 1px solid var(--border);
color: var(--text-dim); border-radius: var(--radius); padding: 0 0.85rem; cursor: pointer;
font-family: var(--font-sans); font-size: 0.82rem; font-weight: 500; transition: color 0.15s, border-color 0.15s; }
.copy-btn:hover { color: var(--select); border-color: var(--select); }
.detail-section { margin-top: 2.25rem; }
.detail-section > h2 { font-family: var(--font-display); font-weight: 600; text-transform: uppercase;
font-size: 1.45rem; letter-spacing: 0.005em; padding-bottom: 0.5rem;
border-bottom: 1px solid var(--border); margin-bottom: 1rem; }
.md h1, .md h2, .md h3 { letter-spacing: -0.01em; margin: 1.4rem 0 0.6rem; line-height: 1.25; }
.md h1 { font-size: 1.35rem; } .md h2 { font-size: 1.15rem; } .md h3 { font-size: 1rem; }
.md p { margin: 0.7rem 0; }
.md ul, .md ol { margin: 0.7rem 0 0.7rem 1.4rem; }
.md li { margin: 0.3rem 0; }
.md .table-wrap { overflow-x: auto; margin: 0.9rem 0; }
.md table { border-collapse: collapse; font-size: 0.86rem; min-width: 100%; }
.md th, .md td { text-align: left; vertical-align: top; padding: 0.4rem 0.75rem 0.4rem 0;
border-bottom: 1px solid var(--border); }
.md th { color: var(--text-dim); font-weight: 600; white-space: nowrap; }
.md code { background: var(--surface-2); border: 1px solid var(--border); padding: 0.08rem 0.35rem;
border-radius: 4px; font-family: var(--font-mono); font-size: 0.84em; }
.md pre { background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius);
padding: 0.85rem 1rem; overflow-x: auto; margin: 0.9rem 0; }
.md pre code { background: none; border: none; padding: 0; font-size: 0.83rem; line-height: 1.55; }
.src pre { background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius);
padding: 1rem 1.1rem; overflow-x: auto; font-family: var(--font-mono);
font-size: 0.82rem; line-height: 1.55; }
.src .k { color: var(--code-k); } .src .s { color: var(--code-s); }
.src .c { color: var(--code-c); font-style: italic; } .src .n { color: var(--code-n); }
.src-meta { display: flex; justify-content: space-between; align-items: baseline; gap: 1rem;
flex-wrap: wrap; margin-bottom: 0.6rem; color: var(--text-dim); font-size: 0.85rem; }
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<h1>attribute-domain-shear</h1>
<p>POINT vs CORNER color-attribute domains on a shared-vertex pinwheel: CORNER stays exact per face while a naive per-wedge POINT loop shears to the last write at the hub. Crisp petals versus a smeared swirl in one frame; the measured shear equals the palette closed form.</p>
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<p class="zoom-hint">Rendered headless by the example itself — click to zoom.</p>
<div class="callout"><span class="tag">witnesses</span> Authoring per-face colors into a POINT-domain attribute overwrites shared vertices once per neighbor; the last write wins and intended colors shear across every shared vertex.</div>
<div class="runline">
<pre id="runCmd">blender --background --python examples/attribute-domain-shear/attribute_domain_shear.py --</pre>
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<section class="detail-section md">
<p>A runnable example that witnesses what <code>POINT</code> versus <code>CORNER</code> <strong>means</strong> on <code>Mesh.color_attributes</code> once the mesh has shared vertices — the domain is not a storage detail, it decides where colors can live. Companion to <a href="https://github.com/TMHSDigital/Blender-Developer-Tools/tree/main/examples/color-attribute-wheel"><code>color-attribute-wheel</code></a> (which covers <code>color_attributes.new()</code> versus the deprecated alias, CORNER sizing == <code>len(loops)</code>, and <code>active_color</code>); this example covers the trap one step later, when AI code knows the API exists but authors per-face colors into a <code>POINT</code>-domain attribute.</p>
<p><strong>Pipeline arc neighbors:</strong> attribute authoring in <a href="https://github.com/TMHSDigital/Blender-Developer-Tools/tree/main/examples/color-attribute-wheel"><code>color-attribute-wheel</code></a>, mesh topology gates in <a href="https://github.com/TMHSDigital/Blender-Developer-Tools/tree/main/examples/mesh-hygiene-audit"><code>mesh-hygiene-audit</code></a>, tangent-space UV contracts in <a href="https://github.com/TMHSDigital/Blender-Developer-Tools/tree/main/examples/triangulate-tangents"><code>triangulate-tangents</code></a>.</p>
<p><strong>What it witnesses:</strong> a pinwheel of K=8 triangles around <strong>one raised hub vertex</strong> shared by every wedge (plus a shared outer ring). The contract, all closed form:</p>
<ul><li><strong>Storage sizes.</strong> CORNER attr data == <code>len(loops)</code> == 3K; POINT attr == <code>len(vertices)</code> == K+1.</li><li><strong>CORNER authoring is exact.</strong> The hub corner of wedge i reads palette[i] within 1e-6 — K faces at one vertex may disagree there.</li><li><strong>POINT naive authoring shears by construction.</strong> A per-wedge authoring loop ("paint each wedge its color") rewrites every shared vertex once per neighbor, and the <strong>last write wins</strong>: the hub reads palette[K-1], ring vert i reads palette[i] — except ring vert 0, which the wrap-around last wedge rewrites to palette[K-1]. The measured mean deviation from intended equals the palette closed form (0.751031) exactly.</li></ul>
<p><strong>What each check catches on failure:</strong> wedge 3 miscolored in the CORNER pass (exit 4); naive writes reversed, so the hub reads palette[0] (exit 5); a ring vert corrupted, breaking the overwrite-ordering witness (exit 6); a constant palette, collapsing the shear so the probe cannot distinguish naive from correct (exit 7). Sizes wrong for the declared domain (exit 3).</p>
<p><strong>Version witness:</strong> output is byte-identical on Blender 4.5.11 LTS and 5.1.2 — the <code>color_attributes</code> domain API is stable across both.</p>
<p><strong>Render as proof:</strong> dual pinwheel from the same closed-form palette the check asserts. CORNER (left) holds eight crisp petals to the hub; naive POINT (right) smears — petal colors bleed across the shared hub and ring verts into a swirl. The broken state is in-frame by design: the right fan <em>is</em> the falsification variant. Fully matte petal materials (<code>Specular IOR Level = 0</code>) so the flat color data carries no specular line, per <code>docs/VISUAL-STYLE.md</code>.</p>
<h2>Run</h2>
<pre><code>blender --background --python attribute_domain_shear.py --
blender --background --python attribute_domain_shear.py -- --no-overwrite
blender --background --python attribute_domain_shear.py -- --output shear.png
blender --background --python attribute_domain_shear.py -- --output shear.png --engine cycles</code></pre>
<h2>Exit codes</h2>
<p>Per-script sequential checks. <code>9</code> is a valid check code; there is no rule against it. <code>10</code> is the shared framing helper.</p>
<div class="table-wrap"><table><thead><tr><th scope="col">Code</th><th scope="col">Meaning</th></tr></thead><tbody><tr><td>0</td><td>Success</td></tr><tr><td>1</td><td>Uncaught exception (FATAL wrapper)</td></tr><tr><td>2</td><td>argparse / usage</td></tr><tr><td>3</td><td>CORNER or POINT attribute size wrong</td></tr><tr><td>4</td><td>CORNER hub corners off wedge color</td></tr><tr><td>5</td><td>POINT hub is not last-write (<code>--no-overwrite</code> lands here)</td></tr><tr><td>6</td><td>Outer ring verts off last-write order</td></tr><tr><td>7</td><td>Measured shear off palette closed form, or ~0</td></tr><tr><td>9</td><td><code>--output</code> produced no file</td></tr><tr><td>10</td><td>Gallery framing violation</td></tr></tbody></table></div>
<p>The <code>blender-smoke</code> workflow runs the check on Blender 5.2 LTS and 4.5 LTS (5.1 on the weekly cron, the <code>needs-5.1</code> PR label, or manual dispatch). Smoke does not pass <code>--output</code> or <code>--no-overwrite</code>.</p>
</section>
<section class="detail-section src">
<h2>Source</h2>
<div class="src-meta">
<code>examples/attribute-domain-shear/attribute_domain_shear.py</code>
<a href="https://github.com/TMHSDigital/Blender-Developer-Tools/tree/main/examples/attribute-domain-shear/attribute_domain_shear.py">View on GitHub →</a>
</div>
<pre><span class="s">"""Attribute domain shear — POINT vs CORNER color attributes on shared verts.
Witnesses the domain-semantics contract of `Mesh.color_attributes` that
AI-generated code trips on after learning `color_attributes.new()` exists:
the DOMAIN chooses where colors live. A `CORNER`-domain attribute stores one
color per loop (face-corner), so the K corners of one shared vertex can each
carry their own face's color. A `POINT`-domain attribute stores one color per
vertex, so a naive per-face authoring loop — "paint every wedge its own
color" — overwrites the shared vertices once per neighbor and the LAST write
wins: intended per-face colors shear across every shared vertex. Companion
to `color-attribute-wheel` (which covers CORNER sizing == loops and
`active_color`): this example covers what the domains *mean* on a fan whose
entire point is one hub vertex shared by every wedge.
Check (all closed form, nothing captured from a prior run):
1. Storage sizes: CORNER attr data == len(loops) == 3*K; POINT == K+1 verts.
2. CORNER authoring is exact: the hub corner of wedge i reads palette[i].
3. POINT naive authoring shears by construction: the hub reads palette[K-1]
(last write wins), EVERY wedge's hub-side loop reads that same color, and
outer ring vert i reads palette[i] (overwritten by wedge i after wedge
i-1 wrote it) — the measured mean deviation from intended equals the
closed-form shear computed from the palette.
By default it runs only the correctness check (no render) — the CI smoke
check. Pass --output to also render a still:
blender --background --python attribute_domain_shear.py -- # check only
blender --background --python attribute_domain_shear.py -- --no-overwrite # must fail
blender --background --python attribute_domain_shear.py -- --output a.png # + render
"""</span>
<span class="k">import</span> bpy, bmesh, sys, os, math, argparse, colorsys
<span class="c"># Shared Layer 1 framing measurement (render path only) — see gallery_framing.py</span>
sys.path.insert(<span class="n">0</span>, os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir))
sys.dont_write_bytecode = <span class="k">True</span> <span class="c"># keep examples/__pycache__ out of the repo tree</span>
<span class="k">import</span> gallery_framing
K = <span class="n">8</span> <span class="c"># pinwheel wedges; hub vertex is shared by all K</span>
HUB_Z = <span class="n">0.55</span> <span class="c"># raised hub: folded-paper pinwheel, not a flat disc</span>
RING_R = <span class="n">1.15</span>
ATTR_C = <span class="s">"PinCorner"</span>
ATTR_P = <span class="s">"PinPoint"</span>
COLOR_EPS = <span class="n">1e-6</span>
<span class="k">def</span> eevee_engine_id():
<span class="k">return</span> <span class="s">"BLENDER_EEVEE"</span> <span class="k">if</span> bpy.app.version >= (<span class="n">5</span>, <span class="n">0</span>, <span class="n">0</span>) <span class="k">else</span> <span class="s">"BLENDER_EEVEE_NEXT"</span>
<span class="k">def</span> palette(k=K):
<span class="s">"""Closed-form wedge hues: saturated HSV wheel in linear-ish floats."""</span>
out = []
<span class="k">for</span> i <span class="k">in</span> range(k):
r, g, b = colorsys.hsv_to_rgb(i / k, <span class="n">0.82</span>, <span class="n">0.95</span>)
out.append((r, g, b, <span class="n">1.0</span>))
<span class="k">return</span> out
<span class="k">def</span> closed_form_shear(pal):
<span class="s">"""Mean per-wedge |palette[i] - palette[K-1]| over RGB — the exact shear a
last-write-wins hub produces. Derived from the palette, never measured."""</span>
last = pal[-<span class="n">1</span>]
<span class="k">return</span> sum(
math.sqrt(sum((pal[i][c] - last[c]) ** <span class="n">2</span> <span class="k">for</span> c <span class="k">in</span> range(<span class="n">3</span>)))
<span class="k">for</span> i <span class="k">in</span> range(len(pal))
) / len(pal)
<span class="k">def</span> build_fan():
<span class="s">"""K triangles around one raised hub vertex; outer ring alternates fold
height so petals read as folded paper under the key light."""</span>
me = bpy.data.meshes.new(<span class="s">"Pinwheel"</span>)
bm = bmesh.new()
<span class="k">try</span>:
hub = bm.verts.new((<span class="n">0.0</span>, <span class="n">0.0</span>, HUB_Z))
ring = []
<span class="k">for</span> i <span class="k">in</span> range(K):
a = <span class="n">2.0</span> * math.pi * i / K
fold = <span class="n">0.14</span> <span class="k">if</span> i % <span class="n">2</span> <span class="k">else</span> <span class="n">0.0</span>
ring.append(bm.verts.new((RING_R * math.cos(a), RING_R * math.sin(a), fold)))
<span class="k">for</span> i <span class="k">in</span> range(K):
bm.faces.new((hub, ring[i], ring[(i + <span class="n">1</span>) % K]))
bm.to_mesh(me)
<span class="k">finally</span>:
bm.free()
<span class="k">return</span> me
<span class="k">def</span> assign_corner(me, pal):
<span class="s">"""Correct path: CORNER domain, one exact wedge color per loop."""</span>
attr = me.color_attributes.new(ATTR_C, type=<span class="s">'FLOAT_COLOR'</span>, domain=<span class="s">'CORNER'</span>)
colors = [<span class="n">0.0</span>] * (len(me.loops) * <span class="n">4</span>)
<span class="k">for</span> poly <span class="k">in</span> me.polygons:
<span class="k">for</span> li <span class="k">in</span> poly.loop_indices:
colors[li * <span class="n">4</span>: li * <span class="n">4</span> + <span class="n">4</span>] = pal[poly.index]
attr.data.foreach_set(<span class="s">"color"</span>, colors)
me.color_attributes.active_color = attr
<span class="k">return</span> attr
<span class="k">def</span> assign_point_naive(me, pal, overwrite=<span class="k">True</span>):
<span class="s">"""The AI mistake: author per-wedge colors into a POINT-domain attribute.
Every wedge rewrites the shared hub (and its leading ring vert), so the
last wedge wins — colors shear across every shared vertex."""</span>
attr = me.color_attributes.new(ATTR_P, type=<span class="s">'FLOAT_COLOR'</span>, domain=<span class="s">'POINT'</span>)
hub_index = <span class="n">0</span> <span class="c"># build_fan creates the hub first</span>
last = K <span class="k">if</span> overwrite <span class="k">else</span> <span class="n">1</span>
<span class="k">for</span> i <span class="k">in</span> range(last):
<span class="c"># naive per-wedge pass: set the hub and both ring verts to palette[i]</span>
attr.data[hub_index].color = pal[i]
attr.data[<span class="n">1</span> + i].color = pal[i]
attr.data[<span class="n">1</span> + (i + <span class="n">1</span>) % K].color = pal[i]
me.color_attributes.active_color = attr
<span class="k">return</span> attr
<span class="k">def</span> check(overwrite=<span class="k">True</span>):
pal = palette()
expect_shear = closed_form_shear(pal)
print(<span class="s">f"</span><span class="s">palette K=</span>{K}<span class="s"> closed_form_shear=</span>{expect_shear:<span class="s">.6f</span>}<span class="s">"</span>)
<span class="c"># --- CORNER: exact authoring ---</span>
me_c = build_fan()
attr_c = assign_corner(me_c, pal)
<span class="k">if</span> len(attr_c.data) != len(me_c.loops) <span class="k">or</span> len(me_c.loops) != <span class="n">3</span> * K:
print(<span class="s">f"</span><span class="s">ERROR: CORNER attr size </span>{len(attr_c.data)}<span class="s"> != loops </span>{len(me_c.loops)}<span class="s">"</span>,
file=sys.stderr)
<span class="k">return</span> <span class="n">3</span>
hub_loop_err = <span class="n">0.0</span>
<span class="k">for</span> poly <span class="k">in</span> me_c.polygons:
got = attr_c.data[poly.loop_indices[<span class="n">0</span>]].color <span class="c"># loop 0 of each tri is the hub</span>
hub_loop_err = max(hub_loop_err,
max(abs(got[c] - pal[poly.index][c]) <span class="k">for</span> c <span class="k">in</span> range(<span class="n">4</span>)))
print(<span class="s">f"</span><span class="s">corner_hub_max_err=</span>{hub_loop_err:<span class="s">.3e</span>}<span class="s"> (must be <= </span>{COLOR_EPS}<span class="s">)</span><span class="s">"</span>)
<span class="k">if</span> hub_loop_err > COLOR_EPS:
print(<span class="s">"ERROR: CORNER hub corners do not carry their wedge's exact color — "</span>
<span class="s">"per-face color at a shared vertex failed"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">4</span>
<span class="c"># --- POINT: the shear, measured against the closed form ---</span>
me_p = build_fan()
attr_p = assign_point_naive(me_p, pal, overwrite=overwrite)
<span class="k">if</span> len(attr_p.data) != len(me_p.vertices) <span class="k">or</span> len(me_p.vertices) != K + <span class="n">1</span>:
print(<span class="s">f"</span><span class="s">ERROR: POINT attr size </span>{len(attr_p.data)}<span class="s"> != verts </span>{len(me_p.vertices)}<span class="s">"</span>,
file=sys.stderr)
<span class="k">return</span> <span class="n">3</span>
hub_got = attr_p.data[<span class="n">0</span>].color
hub_err = max(abs(hub_got[c] - pal[K - <span class="n">1</span>][c]) <span class="k">for</span> c <span class="k">in</span> range(<span class="n">4</span>))
<span class="k">if</span> hub_err > COLOR_EPS:
print(<span class="s">f"</span><span class="s">ERROR: hub reads </span>{tuple(round(c,<span class="n">4</span>) <span class="k">for</span> c <span class="k">in</span> hub_got)}<span class="s"> != last-write </span><span class="s">"</span>
<span class="s">f"</span><span class="s">palette[</span>{K-<span class="n">1</span>}<span class="s">] — last-write-wins contract broken</span><span class="s">"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">5</span>
<span class="c"># Every wedge's hub-side loop reads the same shared color: sample the POINT</span>
<span class="c"># value at the hub through each face's hub loop — one value, K faces.</span>
<span class="c"># Outer ring vert i reads pal[i] — written by wedge i after wedge i-1 —</span>
<span class="c"># EXCEPT vert 0, which the wrap-around last wedge rewrites to pal[K-1].</span>
ring_err = <span class="n">0.0</span>
<span class="k">for</span> i <span class="k">in</span> range(K):
want = pal[i] <span class="k">if</span> i > <span class="n">0</span> <span class="k">else</span> pal[K - <span class="n">1</span>]
got = attr_p.data[<span class="n">1</span> + i].color
ring_err = max(ring_err, max(abs(got[c] - want[c]) <span class="k">for</span> c <span class="k">in</span> range(<span class="n">4</span>)))
print(<span class="s">f"</span><span class="s">point_ring_max_err=</span>{ring_err:<span class="s">.3e</span>}<span class="s"> hub=last_write_ok</span><span class="s">"</span>)
<span class="k">if</span> ring_err > COLOR_EPS:
print(<span class="s">"ERROR: outer ring verts do not read their last write — the "</span>
<span class="s">"overwrite-ordering witness failed"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">6</span>
shear = sum(
math.sqrt(sum((pal[i][c] - hub_got[c]) ** <span class="n">2</span> <span class="k">for</span> c <span class="k">in</span> range(<span class="n">3</span>)))
<span class="k">for</span> i <span class="k">in</span> range(K)
) / K
print(<span class="s">f"</span><span class="s">point_shear measured=</span>{shear:<span class="s">.6f</span>}<span class="s"> closed_form=</span>{expect_shear:<span class="s">.6f</span>}<span class="s">"</span>)
<span class="k">if</span> abs(shear - expect_shear) > <span class="n">1e-6</span>:
print(<span class="s">"ERROR: measured shear does not match the palette closed form — "</span>
<span class="s">"the domain mistake is not being witnessed"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">7</span>
<span class="k">if</span> shear < <span class="n">0.05</span>:
print(<span class="s">"ERROR: shear is ~0 — the probe cannot distinguish naive POINT "</span>
<span class="s">"authoring from correct authoring"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">7</span>
print(<span class="s">f"</span><span class="s">attribute-domain-shear OK corner_exact point_shear=</span>{shear:<span class="s">.6f</span>}<span class="s"> </span><span class="s">"</span>
<span class="s">f"</span><span class="s">(last of </span>{K}<span class="s"> writes wins at 1 shared hub + </span>{K}<span class="s"> shared ring verts)</span><span class="s">"</span>)
<span class="k">return</span> <span class="n">0</span>
<span class="k">def</span> make_attr_material(name, attr_name, matte=<span class="k">True</span>):
mat = bpy.data.materials.new(name)
mat.use_nodes = <span class="k">True</span>
nt = mat.node_tree
bsdf = nt.nodes[<span class="s">"Principled BSDF"</span>]
<span class="k">if</span> matte:
<span class="c"># flat color data: no specular line across the petals (VISUAL-STYLE)</span>
spec = bsdf.inputs.get(<span class="s">"Specular IOR Level"</span>)
<span class="k">if</span> spec <span class="k">is</span> <span class="k">not</span> <span class="k">None</span>:
spec.default_value = <span class="n">0.0</span>
bsdf.inputs[<span class="s">"Roughness"</span>].default_value = <span class="n">0.6</span>
node = nt.nodes.new(<span class="s">"ShaderNodeAttribute"</span>)
node.attribute_type = <span class="s">"GEOMETRY"</span>
node.attribute_name = attr_name
nt.links.new(node.outputs[<span class="s">"Color"</span>], bsdf.inputs[<span class="s">"Base Color"</span>])
<span class="k">return</span> mat
<span class="k">def</span> make_material(name, rgb, rough=<span class="n">0.45</span>, metallic=<span class="n">0.35</span>, emit=<span class="k">None</span>, estr=<span class="n">0.0</span>):
mat = bpy.data.materials.new(name)
mat.use_nodes = <span class="k">True</span>
b = mat.node_tree.nodes[<span class="s">"Principled BSDF"</span>]
b.inputs[<span class="s">"Base Color"</span>].default_value = (*rgb, <span class="n">1.0</span>)
b.inputs[<span class="s">"Roughness"</span>].default_value = rough
b.inputs[<span class="s">"Metallic"</span>].default_value = metallic
<span class="k">if</span> emit <span class="k">is</span> <span class="k">not</span> <span class="k">None</span>:
sock = b.inputs.get(<span class="s">"Emission Color"</span>) <span class="k">or</span> b.inputs[<span class="s">"Emission"</span>]
sock.default_value = (*emit, <span class="n">1.0</span>)
b.inputs[<span class="s">"Emission Strength"</span>].default_value = estr
<span class="k">return</span> mat
<span class="k">def</span> _pinwheel_obj(sc, name, me, loc, rot_z):
ob = bpy.data.objects.new(name, me)
ob.location = loc
ob.rotation_euler = (math.radians(<span class="n">12</span>), <span class="n">0.0</span>, rot_z)
sc.collection.objects.link(ob)
<span class="c"># stem + hub cap: a garden pinwheel on a stick, not a floating disc</span>
stem_me = bpy.data.meshes.new(name + <span class="s">"Stem"</span>)
bm = bmesh.new()
<span class="k">try</span>:
bmesh.ops.create_cone(bm, cap_ends=<span class="k">True</span>, segments=<span class="n">10</span>, radius1=<span class="n">0.05</span>,
radius2=<span class="n">0.06</span>, depth=<span class="n">1.35</span>)
bmesh.ops.translate(bm, vec=(<span class="n">0.0</span>, <span class="n">0.0</span>, -<span class="n">0.72</span>), verts=bm.verts)
bm.to_mesh(stem_me)
<span class="k">finally</span>:
bm.free()
stem_me.materials.append(make_material(<span class="s">"StemMetal"</span>, (<span class="n">0.16</span>, <span class="n">0.17</span>, <span class="n">0.18</span>),
rough=<span class="n">0.4</span>, metallic=<span class="n">0.8</span>))
stem = bpy.data.objects.new(name + <span class="s">"Stem"</span>, stem_me)
stem.location = loc
stem.rotation_euler = (math.radians(<span class="n">12</span>), <span class="n">0.0</span>, rot_z)
sc.collection.objects.link(stem)
cap_me = bpy.data.meshes.new(name + <span class="s">"Cap"</span>)
bm = bmesh.new()
<span class="k">try</span>:
bmesh.ops.create_uvsphere(bm, u_segments=<span class="n">12</span>, v_segments=<span class="n">8</span>, radius=<span class="n">0.075</span>)
bmesh.ops.translate(bm, vec=(<span class="n">0.0</span>, <span class="n">0.0</span>, HUB_Z + <span class="n">0.02</span>), verts=bm.verts)
bm.to_mesh(cap_me)
<span class="k">finally</span>:
bm.free()
cap_me.materials.append(make_material(<span class="s">"CapMetal"</span>, (<span class="n">0.09</span>, <span class="n">0.09</span>, <span class="n">0.095</span>),
rough=<span class="n">0.35</span>, metallic=<span class="n">0.85</span>))
cap = bpy.data.objects.new(name + <span class="s">"Cap"</span>, cap_me)
cap.location = loc
cap.rotation_euler = (math.radians(<span class="n">12</span>), <span class="n">0.0</span>, rot_z)
sc.collection.objects.link(cap)
<span class="k">return</span> ob
<span class="k">def</span> placard(sc, text, loc, size=<span class="n">0.18</span>):
cu = bpy.data.curves.new(text, <span class="s">"FONT"</span>)
cu.body = text
cu.size = size
cu.align_x = <span class="s">"CENTER"</span>
ob = bpy.data.objects.new(text, cu)
ob.location = loc
sc.collection.objects.link(ob)
ob.data.materials.append(make_material(<span class="s">"Label"</span>, (<span class="n">0.9</span>, <span class="n">0.9</span>, <span class="n">0.92</span>),
rough=<span class="n">0.6</span>, metallic=<span class="n">0.0</span>))
<span class="k">return</span> ob
<span class="k">def</span> build_studio(sc):
floor_me = bpy.data.meshes.new(<span class="s">"Floor"</span>)
bm = bmesh.new()
<span class="k">try</span>:
bmesh.ops.create_grid(bm, x_segments=<span class="n">1</span>, y_segments=<span class="n">1</span>, size=<span class="n">30.0</span>)
bm.to_mesh(floor_me)
<span class="k">finally</span>:
bm.free()
fmat = make_material(<span class="s">"Studio"</span>, (<span class="n">0.03</span>, <span class="n">0.032</span>, <span class="n">0.037</span>), rough=<span class="n">0.7</span>, metallic=<span class="n">0.0</span>)
floor_me.materials.append(fmat)
floor = bpy.data.objects.new(<span class="s">"Floor"</span>, floor_me)
sc.collection.objects.link(floor)
wall = bpy.data.objects.new(<span class="s">"Wall"</span>, floor_me.copy())
wall.location = (<span class="n">0.0</span>, <span class="n">9.0</span>, <span class="n">0.0</span>)
wall.rotation_euler = (math.radians(<span class="n">90</span>), <span class="n">0.0</span>, <span class="n">0.0</span>)
sc.collection.objects.link(wall)
world = bpy.data.worlds.new(<span class="s">"World"</span>)
world.use_nodes = <span class="k">True</span>
world.node_tree.nodes[<span class="s">"Background"</span>].inputs[<span class="s">"Color"</span>].default_value = (
<span class="n">0.02</span>, <span class="n">0.021</span>, <span class="n">0.025</span>, <span class="n">1.0</span>,
)
sc.world = world
<span class="k">def</span> light(name, loc, energy, size, col, rot):
ld = bpy.data.lights.new(name, <span class="s">"AREA"</span>)
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) <span class="k">for</span> a <span class="k">in</span> rot)
sc.collection.objects.link(ob)
light(<span class="s">"Key"</span>, (-<span class="n">3.5</span>, -<span class="n">4.5</span>, <span class="n">5.5</span>), <span class="n">480.0</span>, <span class="n">4.5</span>, (<span class="n">1.0</span>, <span class="n">0.96</span>, <span class="n">0.9</span>), (<span class="n">48</span>, <span class="n">0</span>, -<span class="n">35</span>))
light(<span class="s">"Fill"</span>, (<span class="n">5.0</span>, -<span class="n">3.5</span>, <span class="n">2.5</span>), <span class="n">120.0</span>, <span class="n">9.0</span>, (<span class="n">0.75</span>, <span class="n">0.85</span>, <span class="n">1.0</span>), (<span class="n">65</span>, <span class="n">0</span>, <span class="n">50</span>))
light(<span class="s">"Rim"</span>, (<span class="n">1.5</span>, <span class="n">4.5</span>, <span class="n">3.5</span>), <span class="n">280.0</span>, <span class="n">3.0</span>, (<span class="n">0.6</span>, <span class="n">0.78</span>, <span class="n">1.0</span>), (-<span class="n">55</span>, <span class="n">0</span>, <span class="n">170</span>))
light(<span class="s">"Wedge"</span>, (<span class="n">2.5</span>, <span class="n">5.5</span>, <span class="n">4.0</span>), <span class="n">400.0</span>, <span class="n">6.0</span>, (<span class="n">1.0</span>, <span class="n">0.72</span>, <span class="n">0.42</span>), (-<span class="n">68</span>, <span class="n">0</span>, <span class="n">190</span>))
<span class="k">return</span> floor, wall
<span class="k">def</span> render_still(path, engine):
<span class="s">"""Dual pinwheel: CORNER (crisp petals to the hub) vs naive POINT (last
write smears the shared hub + ring verts). Colors come from the same
closed-form palette the check asserts."""</span>
bpy.ops.wm.read_factory_settings(use_empty=<span class="k">True</span>)
sc = bpy.context.scene
pal = palette()
me_c = build_fan()
assign_corner(me_c, pal)
me_c.materials.append(make_attr_material(<span class="s">"MatCorner"</span>, ATTR_C))
left = _pinwheel_obj(sc, <span class="s">"Corner"</span>, me_c, (-<span class="n">1.15</span>, <span class="n">0.0</span>, <span class="n">1.35</span>), math.radians(-<span class="n">8</span>))
me_p = build_fan()
assign_point_naive(me_p, pal)
me_p.materials.append(make_attr_material(<span class="s">"MatPoint"</span>, ATTR_P))
right = _pinwheel_obj(sc, <span class="s">"Point"</span>, me_p, (<span class="n">1.15</span>, <span class="n">0.0</span>, <span class="n">1.35</span>), math.radians(<span class="n">8</span>))
p_corner = placard(sc, <span class="s">"CORNER"</span>, (-<span class="n">1.15</span>, -<span class="n">1.05</span>, <span class="n">0.02</span>), size=<span class="n">0.13</span>)
p_point = placard(sc, <span class="s">"POINT — last write wins"</span>, (<span class="n">1.15</span>, -<span class="n">1.05</span>, <span class="n">0.02</span>), size=<span class="n">0.10</span>)
floor, wall = build_studio(sc)
cam_data = bpy.data.cameras.new(<span class="s">"Cam"</span>)
cam_data.lens = <span class="n">48.0</span>
cam = bpy.data.objects.new(<span class="s">"Cam"</span>, cam_data)
cam.location = (<span class="n">0.0</span>, -<span class="n">6.4</span>, <span class="n">4.6</span>)
sc.collection.objects.link(cam)
aim = bpy.data.objects.new(<span class="s">"Aim"</span>, <span class="k">None</span>)
aim.location = (<span class="n">0.0</span>, <span class="n">0.0</span>, <span class="n">0.8</span>)
sc.collection.objects.link(aim)
tr = cam.constraints.new(<span class="s">"TRACK_TO"</span>)
tr.target = aim
tr.track_axis = <span class="s">"TRACK_NEGATIVE_Z"</span>
tr.up_axis = <span class="s">"UP_Y"</span>
sc.camera = cam
sc.render.engine = <span class="s">"CYCLES"</span> <span class="k">if</span> engine == <span class="s">"cycles"</span> <span class="k">else</span> eevee_engine_id()
<span class="k">if</span> engine == <span class="s">"cycles"</span>:
sc.cycles.device = <span class="s">"CPU"</span>
sc.cycles.samples = <span class="n">64</span>
sc.cycles.use_denoising = <span class="k">True</span>
<span class="k">else</span>:
<span class="k">try</span>:
sc.eevee.taa_render_samples = <span class="n">64</span>
<span class="k">except</span> AttributeError:
<span class="k">pass</span>
sc.render.resolution_x = <span class="n">1280</span>
sc.render.resolution_y = <span class="n">720</span>
sc.render.image_settings.file_format = <span class="s">"PNG"</span>
sc.render.filepath = path
<span class="c"># Standard, always: AgX would bend the closed-form palette the check asserts</span>
sc.view_settings.view_transform = <span class="s">"Standard"</span>
<span class="c"># Layer 1 framing gate (silhouette matte) — exit 10 on violation.</span>
hero = [left, right]
elements = hero + [p_corner, p_point]
fcode = gallery_framing.check_framing(
sc, cam,
hero=hero,
elements=elements,
stage=[floor, wall],
)
<span class="k">if</span> fcode:
<span class="k">return</span> fcode
bpy.ops.render.render(write_still=<span class="k">True</span>)
<span class="k">if</span> <span class="k">not</span> (os.path.exists(path) <span class="k">and</span> os.path.getsize(path) > <span class="n">0</span>):
print(<span class="s">"ERROR: render produced no file"</span>, file=sys.stderr)
<span class="k">return</span> <span class="n">9</span>
<span class="k">return</span> <span class="n">0</span>
<span class="k">def</span> main():
argv = sys.argv[sys.argv.index(<span class="s">"--"</span>) + <span class="n">1</span>:] <span class="k">if</span> <span class="s">"--"</span> <span class="k">in</span> sys.argv <span class="k">else</span> []
p = argparse.ArgumentParser()
p.add_argument(<span class="s">"--output"</span>, default=<span class="k">None</span>, help=<span class="s">"optional: render a still PNG here"</span>)
p.add_argument(<span class="s">"--engine"</span>, default=<span class="s">"eevee"</span>, choices=(<span class="s">"eevee"</span>, <span class="s">"cycles"</span>),
help=<span class="s">"render engine for --output (cycles for GPU-less hosts)"</span>)
p.add_argument(<span class="s">"--no-overwrite"</span>, action=<span class="s">"store_true"</span>,
help=<span class="s">"write only the first POINT wedge (must fail)"</span>)
args = p.parse_args(argv)
print(<span class="s">f"</span><span class="s">binary version: </span>{bpy.app.version}<span class="s"> (</span>{bpy.app.version_string}<span class="s">)</span><span class="s">"</span>)
bpy.ops.wm.read_factory_settings(use_empty=<span class="k">True</span>)
code = check(overwrite=<span class="k">not</span> args.no_overwrite)
<span class="k">if</span> code:
<span class="k">return</span> code
<span class="k">if</span> args.output:
rcode = render_still(os.path.abspath(args.output), args.engine)
<span class="k">if</span> rcode:
<span class="k">return</span> rcode
print(<span class="s">f"</span><span class="s">rendered still </span>{args.output}<span class="s">"</span>)
print(<span class="s">"attribute-domain-shear OK"</span>)
<span class="k">return</span> <span class="n">0</span>
<span class="k">if</span> __name__ == <span class="s">"__main__"</span>:
<span class="k">try</span>:
sys.exit(main())
<span class="k">except</span> Exception <span class="k">as</span> e:
<span class="k">import</span> traceback
traceback.print_exc()
print(<span class="s">f"</span><span class="s">FATAL: </span>{e}<span class="s">"</span>, file=sys.stderr)
sys.exit(<span class="n">1</span>)
</pre>
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