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fix #427: sky drawn without fog like retail; world fog range is the keyframe's authored MinWorldFog/MaxWorldFog

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Two April stand-ins, neither registered, met at the horizon from altitude as
a hard line between the dome's rim and the fog-coloured clear:

1. sky.frag fogged every non-additive sky layer with a 0.2 floor. Retail's
   GameSky::Draw @0x00506FF0 disables fixed-function fog around the whole
   sky draw unless an AdminEnvirons fog override is active (SetFFFogEnable(
   LScape::m_override_enabled ? 1 : 0)); additive layers stay unfogged via
   SetFFFogAlphaDisabled(1) at D3DPolyRender::SetSurface 0x59c882. The sky
   pass now sets ApplyFog only for (override active && !additive), with no
   floor.
2. WorldRenderFrameBuilder overwrote the authored fog range with one derived
   from the streaming window (538..2189 m always). Retail sets FOGSTART/
   FOGEND straight from the keyframe's MinWorldFog/MaxWorldFog
   (SkyDesc::GetWorldFog @0x00500CE0 -> SetFFFogProperties @0x005A2F70) with
   no draw-distance scaling; zfar is a constant 4000 m. The builder now
   leaves SceneLightingUbo.Build's values alone; ACDREAM_FOG_START_MULT /
   _END_MULT are deleted from RuntimeOptions.

Guards: SkyFogRuleTests (source-level, the sky renderer has no hermetic
harness); sky.frag.spv re-pinned in VulkanShaderManifestTests with the
reason. Research note 2026-04-23-sky-fog.md carries a correction banner.
App hermetic 6,070/0, Core 4,707/0 (Release). Owner look gate owed: night
and rain fog are now retail's shorter authored ranges.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-08-23 13:42:42 +02:00
parent 517d17b4b3
commit cc42edc8e3
11 changed files with 180 additions and 62 deletions
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10
docs/research/2026-04-23-sky-fog.md
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@ -1,3 +1,13 @@
> **CORRECTION 2026-08-23 (#427).** This note assumed retail fogs its sky
> meshes ("the sky dome mesh is at a distance where fog contribution
> dominates"). It does not: `GameSky::Draw @0x00506FF0` disables fixed-
> function fog around the entire sky draw unless an AdminEnvirons fog
> override is active. The dome's horizon colour is the authored texture plus
> the keyframe tint. The `SKY_FOG_FLOOR = 0.2` clamp that this assumption
> produced was removed the same day. Q3's terrain-fog conclusions (authored
> `MinWorldFog/MaxWorldFog` applied directly, no scaling) stand and are now
> what the client does.
# Sky Fog — How Retail Applies Fog to Sky Meshes (Decompile Trace)
**Date:** 2026-04-23