Two independent brightness bugs were compounding to make rain ~6.7×
too bright at the cylinder rim, and clouds full-bright instead of
time-of-day-tinted:
**Fix 1 — Surface.Translucency was never plumbed to the shader.**
Retail's D3DPolyRender::SetSurface at 0x59c767: when the Surface's
Translucent (0x10) bit is set, its translucency float drives per-vertex
alpha (curr_alpha = ftol(0.5 × 255) = 127). ACViewer
(TextureCache.cs:142) and WorldBuilder (ObjectMeshManager.cs:1115) both
encode the same as `opacity = (1 - x)`. acdream read only Surface.Type
and Surface.Luminosity in GfxObjMesh.Build() — Surface.Translucency
(the float) was never read, never stored, never reached the shader.
For the rain Surface 0x080000C5 (Translucency=0.5) this meant rain
streaks were at full alpha=1.0 instead of 0.5 — 2× brighter than retail
under the (SrcAlpha, One) blend.
Plumbed end-to-end:
GfxObjSubMesh.SurfTranslucency (init float, default 0)
GfxObjMesh.Build() reads surface.Translucency next to .Luminosity
SubMeshGpu.SurfTranslucency carries it to draw time
SkyRenderer.RenderPass writes uniform `uSurfTranslucency`
sky.frag final alpha: a = sampled.a × (1 - uTransparency) ×
(1 - uSurfTranslucency)
Bonus reach: cloud surface 0x08000023 has Translucency=0.25 → clouds
also dimmed by 25%, more retail-faithful overall.
**Fix 2 — Emissive default was 1.0 instead of the surface's actual Luminosity.**
The sky shader's `effEmissive = (luminosity > 0) ? luminosity : sub.SurfLuminosity`
fallback never fired because the local `luminosity` defaulted to 1f (always
> 0). Every sky mesh got effEmissive=1.0, saturating vTint to white before
the alpha blend. The comment claimed the fallback was active; the code
disagreed.
Empirical sky-surface LUMINOUS audit (RainMeshProbe a6e7108) found that
NO Dereth sky surface carries the SurfaceType.Luminous flag (0x40) —
the previous code comment that did was wrong. The differentiator is
purely the Surface.Luminosity FLOAT:
dome/sun/moon: Lum=1.0 → vTint saturates → texture passthrough
stars/clouds: Lum=0.0 → vTint = ambient + sun·N·L → time-of-day tint
rain: Lum=0.1484 → faint emissive baseline + lit additions
Refactored:
replaceLuminosity = NaN sentinel for "no replace override"
rep.Luminosity > 0 → set replaceLuminosity to override value
rep.MaxBright > 0 → cap replaceLuminosity at MaxBright
effEmissive = NaN ? sub.SurfLuminosity : replaceLuminosity
Dead uniform `uLuminosity` removed from sky.frag and SkyRenderer SetFloat
call — the redundant multiply was already commented-out earlier this
year (would have double-dimmed clouds), and the uniform value was unused
in the fragment.
Visual verification (Holtburg, live ACE, Rainy DG forced and natural
LCG-picked): rain rim is no longer visible; cloud direction matches
retail when the same DayGroup is active; sky lighting transitions through
day cycle with appropriate time-of-day tint on stars/clouds.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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