Phase 2 of the sky port. Empirically confirmed from the Phase 1 dump
(ACDREAM_DUMP_SKY=1 on the live Dereth region): retail distinguishes
self-illuminated sky meshes from lit ones by the `Surface.Luminosity`
FLOAT field (0..1), NOT by the `SurfaceType.Luminous` flag bit (none of
Dereth's sky meshes have the flag set).
Observed values on the 4 currently-visible sky GfxObjs:
GfxObj 0x010015EE (dome, 4 surfaces) Luminosity = 1.0
GfxObj 0x010015EF (upper cloud) Luminosity = 0.0
GfxObj 0x01004C36 (lower drift cloud) Luminosity = 0.0
GfxObj 0x01001348 (sun/moon additive) Luminosity = 1.0
Retail uses this as an emissive coefficient in the per-vertex lighting
formula (decompiled chunk_00500000.c:7535 FUN_00508010 + chunk_00530000.c
AdjustPlanes per-vertex math):
tint = clamp(vec3(Luminosity) + AmbColor*AmbBright
+ max(dot(N, -sunDir), 0) * DirColor*DirBright,
0.0, 1.0)
fragment = texture * tint
When Luminosity=1.0 the clamp saturates → full texture brightness
regardless of time of day (dome gradient preserved; sun/moon always
bright). When Luminosity=0.0 only the ambient + diffuse term drives the
tint, so clouds pick up the time-of-day ambient (purple at midnight
per AmbColor=(200,100,255)×AmbBright=0.4 ≈ (0.31,0.16,0.40); warm tan
at dusk; pale-cool at noon).
Also empirically confirmed: raw SkyObjectReplace Transparent/Luminosity
/MaxBright are in 0..100 percent range (observed 11, 15, 22, 66, 100,
and -1 sentinel). The `/100` divide in SkyDescLoader (eeae83a) is
retail-correct; `_DAT_007a1870` in the decompile must be 0.01f.
Code changes:
- src/AcDream.Core/Meshing/GfxObjSubMesh.cs: new `Luminosity` field on
the per-submesh record (0..1, defaults to 0 for non-sky meshes).
- src/AcDream.Core/Meshing/GfxObjMesh.cs: pull Surface.Luminosity when
building submeshes (alongside existing Translucency capture).
- src/AcDream.App/Rendering/Sky/SkyRenderer.cs:
- SubMeshGpu gains SurfLuminosity, propagated from GfxObjSubMesh.
- Render() pushes uAmbientColor/uSunColor/uSunDir once per frame from
the interpolated keyframe; uEmissive once per submesh.
- uTint uniform removed (replaced by the vTint varying computed in
the vertex shader).
- src/AcDream.App/Rendering/Shaders/sky.vert: computes vTint per-vertex
using the retail AdjustPlanes formula.
- src/AcDream.App/Rendering/Shaders/sky.frag: consumes vTint, drops
uTint uniform. uLuminosity (the per-keyframe SkyObjectReplace
override) still applied as a final scalar multiply.
Expected visual difference from Phase 1 baseline:
- Dome gradient: IDENTICAL (Luminosity=1 saturates).
- Sun / moon: IDENTICAL (Luminosity=1 saturates, additive blend).
- Clouds: now tinted by time of day. Midnight → purple haze. Noon →
pale cool. Dusk → warm tan.
Open questions (unchanged from Phase 1 doc):
- Does the 15s LightTickSize throttling need porting? Phase 3.
- Does FUN_00532440 (AdjustPlanes per-cell terrain relight) need
porting for non-sky geometry to follow the sky? Phase 3.
Build + 717 tests green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Wire the existing LightManager + WorldTimeService state into visible
rendering. Every draw call (terrain, static mesh, instanced mesh, sky)
now shares one SceneLighting UBO at binding=1 carrying:
- 8 Light slots (Directional / Point / Spot, retail hard-cutoff)
- Ambient RGB + active light count
- Fog start/end/mode + color + lightning flash scalar
- Camera world position + day fraction
The CPU side (SceneLightingUbo in Core.Lighting) is a POD struct that
gets BufferSubData'd once per frame from GameWindow.OnRender. Shaders
read the block via `layout(std140, binding = 1) uniform SceneLighting`
— no per-program uniform uploads.
Shader changes:
- mesh.frag + mesh_instanced.frag accumulate 8 dynamic lights per
fragment using the retail no-attenuation hard-cutoff model
(r13 §10.2 / §13.1). Sun reads slot 0; spots use hard cos-cone test.
Additive lightning flash + linear fog layered on top. Saturate
clamps per-channel to 1.0.
- terrain.vert bakes AdjustPlanes sun+ambient per vertex using the
retail MIN_FACTOR = 0.08 ambient floor (r13 §7). terrain.frag adds
fog + flash on top of the baked vertex color.
- mesh.vert + mesh_instanced.vert emit vWorldPos so the fragment
stage can do per-pixel lighting against world-space positions.
- New sky.vert / sky.frag pair — unlit, scroll-UV, camera-centered,
with its own 0.1..1e6 far plane. Ports WorldBuilder's skybox.
SkyRenderer (new file in App/Rendering/Sky/) ports WorldBuilder's
SkyboxRenderManager verbatim for the C# idiom: zeroed view translation,
dedicated projection, depth mask off, iterate each visible SkyObject
in the day group, apply arc transform (Z rot for heading + Y rot for
arc sweep), feed TexVelocityX/Y as a scrolling UV offset, apply
per-keyframe SkyObjectReplace overrides (mesh swap + transparency +
luminosity) for overcast / dusk cloud variants.
GameWindow integration:
- OnLoad parses Region (0x13000000) into LoadedSkyDesc and hot-swaps
WorldTime's provider to the dat-accurate keyframes. Seeds to noon
for offline rendering. Creates the SceneLightingUboBinding and the
SkyRenderer.
- OnRender: set clear color from atmosphere fog, tick WeatherSystem,
spawn/stop rain/snow camera-local emitters on kind change, feed
sun to LightManager (zero intensity indoors — r13 §13.7), tick
LightManager against viewer pos, build + upload the UBO, draw
sky before terrain, draw terrain + static + instanced using the
shared UBO.
5 new UBO packing tests (struct sizes, slot population, 8-light cap,
directional slot 0).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Erik