Three root causes regressed the Holtburg lifestone since the WB rendering
migration (Phase N.5 retirement amendment, commit dcae2b6, 2026-05-08).
All confirmed via temporary [LIFESTONE-DIAG] instrumentation and visually
verified by the user through the +Acdream test character.
1. **Alpha-test discard** in mesh_modern.frag transparent pass killed
high-α pixels of dat-flagged transparent surfaces. Native AC
transparent surfaces routinely include effectively-opaque pixels —
e.g. the lifestone crystal core (surface 0x080011DE) — that compose
correctly under (SrcAlpha, 1-SrcAlpha) blending. The original N.5
§2 rationale ("high-α belongs in opaque pass") doesn't hold for
surfaces flagged transparent at the dat level: those pixels can't
reach the opaque pass at all. Fix: remove `α >= 0.95 discard` from
the transparent pass, keep `α < 0.05 discard` as a fragment-cost
optimization (skip totally-empty pixels).
2. **Cull state** for the transparent pass was unset by
WbDrawDispatcher after the N.5 retirement amendment deleted
StaticMeshRenderer.cs (which had the Phase 9.2 setup at commit
6f1971a, 2026-04-11). Closed-shell translucents — lifestone crystal,
glow gems — need GL_CULL_FACE + GL_BACK + GL_CCW in the transparent
pass; otherwise back faces composite over front faces in iteration
order under DepthMask(false). Fix: re-establish Phase 9.2's exact
GL state setup at the top of Phase 8.
3. **uDrawIDOffset uniform** was missing from mesh_modern.vert.
gl_DrawIDARB resets to 0 at the start of each
glMultiDrawElementsIndirect call, so the transparent pass — which
begins later in the indirect buffer — was fetching
Batches[0..transparentCount) instead of its actual section at
Batches[opaqueCount..end). The lifestone crystal ended up reading
the FIRST OPAQUE batch's TextureHandle every frame; as the camera
moved and the front-to-back opaque sort reordered which group
landed at BatchData[0], the crystal's apparent texture flickered to
whatever sat first — typically the player character's body parts.
Fix: add `uniform int uDrawIDOffset` to the vertex shader, change
Batches[gl_DrawIDARB] → Batches[uDrawIDOffset + gl_DrawIDARB], and
set the uniform per-pass in WbDrawDispatcher (0 for opaque,
_opaqueDrawCount for transparent). Mirrors WorldBuilder's
BaseObjectRenderManager.cs line 845.
Tests: 1688/1696 passing (8 pre-existing physics/input failures
unchanged). N.5b conformance sentinel 94/94 clean.
Visual: Holtburg lifestone now renders with the spinning blue crystal
correctly composed over the pedestal. Other transparent content (glass,
particle effects, NPC clothing) is unaffected — the same uniform fix
applies globally and is correct for all transparent draws.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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