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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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25
src/AcDream.App/Rendering/Sky/SkyRenderer.cs
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@ -372,18 +372,19 @@ public sealed partial class SkyRenderer : IDisposable
// with texture alpha and keyframe transparency.
_params.SurfOpacity = sub.SurfOpacity;
// Retail D3DPolyRender::SetSurface at 0x59c882 calls
// SetFFFogAlphaDisabled(1) when the Additive flag (0x10000)
// is set on the Surface — so the sun, moon, stars, and any
// additive cloud sheet are drawn WITHOUT fog. Skipping fog
// on additive surfaces keeps the sun bright at horizon
// dusk/dawn (where fog would otherwise dim it to fog color).
// Non-additive sky meshes (the dome/background layers)
// still mix toward keyframe fog with the floor mitigation
// in sky.frag. That restores the broad green/purple Rainy
// DayGroup tint behind the cloud sheet while raw-additive
// 0x08000023 remains unfogged and keeps the pink detail.
_params.ApplyFog = sub.DisableFog ? 0f : 1f;
// Retail GameSky::Draw @0x00506FF0 draws the whole sky with
// fixed-function fog DISABLED unless an AdminEnvirons fog
// override is active (SetFFFogEnable(LScape::
// m_override_enabled ? 1 : 0) around the sky draw). Within
// that, D3DPolyRender::SetSurface at 0x59c882 calls
// SetFFFogAlphaDisabled(1) for Additive surfaces (sun,
// moon, stars, additive cloud sheets), so those are never
// fogged. The dome's horizon tint is the authored texture
// plus keyframe tint — not fog — which is why the frame's
// fog-coloured clear meets the dome cleanly at its rim.
// (Until 2026-08-23 every non-additive layer was fogged
// with a 0.2 floor; see sky.frag for the symptom.)
_params.ApplyFog = environOverrideActive && !sub.DisableFog ? 1f : 0f;
// Sky meshes need per-object wrap mode driven by the
// mesh's authored UV range, not by TexVelocity: