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docs(issues): #37 humanoid coat doesn't extend up to neck (env-var diagnostics committed)

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Filed as #37 after a ~3 hr investigation that ruled out animation source,
backface culling/winding, palette overlay, and head-GfxObj polygons.

Confirmed:
- Stub is from part 9 (upper torso/coat) post-AnimPartChange (gfx 0x0100120D)
- Part 9's both surfaces ARE matched by our 2 TextureChanges
- Server data complete; composition formula matches ACME + retail decomp

Untested hypothesis space (next session):
- Texture decode chain (compare our SurfaceDecoder vs ACME TextureHelpers)
- Polygon-to-surface index off-by-one on part 9
- Multi-layer texture composition AC may do
- UV mapping bug

Diagnostic env vars committed to source for next-session reuse:
- ACDREAM_HIDE_PART=N — hide specific humanoid part to localize bugs
- ACDREAM_NO_CULL=1 — disable backface culling
- ACDREAM_DUMP_CLOTHING=1 — dump APC + TC + per-part Surface chain coverage

Bug was originally reported as "head/neck protrudes forward"; the apparent
forward shift turned out to be an optical illusion from the missing
coat collar. Math + cdb-ground-truth + ACME comparison confirmed the
head placement is correct retail-faithful — see #37 for the long write-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-05-01 16:05:33 +02:00
parent 3361641655
commit 09e013b7bd
3 changed files with 166 additions and 3 deletions
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21
src/AcDream.App/Rendering/InstancedMeshRenderer.cs
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@ -207,6 +207,11 @@ public sealed unsafe class InstancedMeshRenderer : IDisposable
}
// ── Pass 1: Opaque + ClipMap ──────────────────────────────────────────
// Diagnostic: ACDREAM_NO_CULL=1 disables backface culling entirely.
if (string.Equals(Environment.GetEnvironmentVariable("ACDREAM_NO_CULL"), "1", StringComparison.Ordinal))
{
_gl.Disable(EnableCap.CullFace);
}
foreach (var (key, grp) in _groups)
{
if (!_gpuByGfxObj.TryGetValue(key.GfxObjId, out var subMeshes))
@ -268,9 +273,19 @@ public sealed unsafe class InstancedMeshRenderer : IDisposable
// ── Pass 2: Translucent (AlphaBlend, Additive, InvAlpha) ─────────────
_gl.Enable(EnableCap.Blend);
_gl.DepthMask(false);
_gl.Enable(EnableCap.CullFace);
_gl.CullFace(TriangleFace.Back);
_gl.FrontFace(FrontFaceDirection.Ccw);
// Diagnostic: ACDREAM_NO_CULL=1 disables backface culling (used 2026-05-01
// to test if our mesh winding (0,i,i+1) vs ACME's (i+1,i,0) is causing
// visible polygons to be culled, especially around the neck/coat seam).
if (string.Equals(Environment.GetEnvironmentVariable("ACDREAM_NO_CULL"), "1", StringComparison.Ordinal))
{
_gl.Disable(EnableCap.CullFace);
}
else
{
_gl.Enable(EnableCap.CullFace);
_gl.CullFace(TriangleFace.Back);
_gl.FrontFace(FrontFaceDirection.Ccw);
}
foreach (var (key, grp) in _groups)
{