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fix(render): A7 point-light shape — per-vertex Gouraud + faithful calc_point_light (wrap + norm)

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The torch/point-light look was wrong two ways, both now fixed against the
named retail decomp (calc_point_light 0x0059c8b0) via our verified
LightBake.PointContribution port:

1. Per-PIXEL → per-VERTEX. accumulateLights moved from mesh_modern.frag to
   mesh_modern.vert so point lights Gouraud-interpolate across each triangle
   the way retail's fixed-function T&L does. The per-pixel eval made a tight,
   hard-edged "spotlight" pool on flat walls; per-vertex is a soft, broad
   gradient. frag now just consumes the interpolated vLit (+ fog + flash).

2. Simplified ramp → faithful calc_point_light shape. The live point/spot
   branch was max(0,N·L) × linear(1−d/range) × cap — missing two terms our
   LightBake.cs port already has:
     • half-Lambert WRAP (1/1.5)·(N·D + 0.5·d), D un-normalised — a face
       angled away from a torch still catches light (retail's soft terminator)
       instead of snapping to black.
     • distance-cube NORM branch norm = distsq>1 ? distsq·d : d — inverse-
       square-ish soft far halo + punchy near field, vs the flat linear ramp.
   Per-channel no-blowout cap (min(scale·color, color)) retained.

The per-channel cap was also added to the legacy mesh.frag for consistency.

A read-only retail-vs-acdream lighting audit (11-agent workflow) confirmed
these two as the cause of the "better but a bit off" look and cleared the
ambient/sun/terrain/color-space chain as already faithful. Remaining
confirmed divergences (per-object light selection; dungeon static vertex
bake) are filed as the next fixes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-06-15 22:27:27 +02:00
parent d2b8a51426
commit aa94cedc38
3 changed files with 93 additions and 41 deletions
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5
src/AcDream.App/Rendering/Shaders/mesh.frag
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@ -84,7 +84,10 @@ vec3 accumulateLights(vec3 N, vec3 worldPos) {
float cos_l = dot(-Ldir, uLights[i].dirAndRange.xyz);
atten *= (cos_l > cos_edge) ? 1.0 : 0.0;
}
lit += Lcol * ndl * atten;
// Retail per-channel "no-blowout" cap (calc_point_light 0x0059c8b0): a single
// point/spot light can't push a channel past its own colour, regardless of
// intensity (~100) — kills the close-torch overblow (#93). See mesh_modern.frag.
lit += min(Lcol * ndl * atten, uLights[i].colorAndIntensity.xyz);
}
}
}