sky(phase-2): retail-verbatim per-vertex lighting via Surface.Luminosity
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>
This commit is contained in:
Erik
parent
58afd4850f
commit
aa2e20a42e
5 changed files with 152 additions and 78 deletions
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@ -74,18 +74,21 @@ public sealed unsafe class SkyRenderer : IDisposable
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/// terrain / meshes / debug lines / overlay land on top.
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///
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/// <para>
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/// <paramref name="keyframe"/> is accepted for forward-compatibility
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/// with the retail-verbatim per-vertex lighting path (see
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/// <c>docs/research/2026-04-23-sky-retail-verbatim.md</c>). It is
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/// NOT currently consumed by the shader — sky meshes render at
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/// <c>uTint = white</c> (texture passthrough). A prior experiment
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/// multiplied alpha-blended submeshes by <c>keyframe.AmbientColor</c>
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/// to tint clouds; this dimmed the sky dome's baked gradient
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/// (user-verified regression) and was reverted. Retail actually
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/// routes sky meshes through the normal mesh pipeline with
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/// Surface.Type.Luminous controlling lit-vs-unlit per submesh; the
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/// correct port lives downstream in Phase 2 once we have the live
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/// Surface flags dumped.
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/// Each submesh renders with retail's per-vertex lighting formula:
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/// <c>tint = clamp(emissive + ambient + max(dot(N, -sunDir), 0) * sunColor, 0, 1)</c>
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/// where <c>emissive</c> is the submesh's <c>Surface.Luminosity</c>
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/// float (1.0 for dome + sun + moon → texture passthrough via
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/// saturation; 0.0 for clouds → get the full time-of-day tint).
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/// <paramref name="keyframe"/> supplies the AmbientColor and SunColor
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/// already pre-multiplied by AmbBright / DirBright (loader-side).
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/// </para>
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/// <para>
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/// See <c>docs/research/2026-04-23-sky-retail-verbatim.md</c> §6 for
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/// the full decompile citation. The empirical Dereth dump (
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/// <c>ACDREAM_DUMP_SKY=1</c>, logged 2026-04-23) confirmed the
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/// <c>SurfaceType.Luminous</c> flag bit is NOT set on any Dereth sky
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/// mesh — the differentiator is the <c>Surface.Luminosity</c> FLOAT
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/// field.
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/// </para>
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/// </summary>
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public void Render(
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@ -116,23 +119,24 @@ public sealed unsafe class SkyRenderer : IDisposable
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_shader.SetMatrix4("uSkyView", skyView);
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_shader.SetMatrix4("uSkyProjection", skyProj);
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// Retail per-vertex lighting inputs (AdjustPlanes formula).
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// AmbColor/SunColor are already × AmbBright/DirBright from
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// SkyDescLoader. SunDir is the unit vector FROM surface TO sun
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// derived from the keyframe's DirHeading/DirPitch.
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_shader.SetVec3("uAmbientColor", keyframe.AmbientColor);
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_shader.SetVec3("uSunColor", keyframe.SunColor);
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_shader.SetVec3("uSunDir",
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AcDream.Core.World.SkyStateProvider.SunDirectionFromKeyframe(keyframe));
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// Save + override GL state.
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_gl.DepthMask(false);
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_gl.Disable(EnableCap.DepthTest);
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_gl.Disable(EnableCap.CullFace);
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_gl.Enable(EnableCap.Blend);
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// Default blend — overridden per-submesh inside the inner loop based
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// on the Surface's TranslucencyKind + Luminous flag. Sun/moon/stars
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// in retail use Additive (their texture has a black background and a
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// bright body painted on top; additive blending ignores the black and
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// lets the body glow over the sky gradient). Clouds use AlphaBlend.
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// Without per-object blend, sun renders as "black square with sun in
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// it" because our default alpha-blend treats the black background as
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// opaque. See SurfaceType enum (DatReaderWriter.Enums.SurfaceType):
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// Additive = 0x10000 → GL_ONE / GL_ONE
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// Luminous = 0x40 → additive for sky purposes
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// Alpha = 0x100 / Translucent = 0x10 → GL_SRC_ALPHA / GL_ONE_MINUS_SRC_ALPHA
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// Base1ClipMap = 0x04 → alpha with shader discard
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// Default blend — overridden per-submesh inside the inner loop.
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// Additive surfaces (sun/moon/stars via SurfaceType.Additive =
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// 0x10000) get GL_SRC_ALPHA / GL_ONE; alpha-blended (clouds, dome
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// with Alpha flag) get GL_SRC_ALPHA / GL_ONE_MINUS_SRC_ALPHA.
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_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
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// Look up the keyframe's override list so we can apply
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@ -183,17 +187,6 @@ public sealed unsafe class SkyRenderer : IDisposable
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_shader.SetVec2("uUvScroll", new Vector2(uOffset, vOffset));
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_shader.SetFloat("uTransparency", transparent);
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_shader.SetFloat("uLuminosity", luminosity);
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// uTint stays white: retail renders sky meshes as texture
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// passthrough (the gradient lives in the mesh texture, not in
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// a shader ambient multiply). D3DRS_AMBIENT is set to 0 once
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// at retail device-init and never changes per-frame — verified
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// in chunk_005A0000.c (state 0x8b = 139, only external caller
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// is the default-reset at line 704). The "cloud tint" effect
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// comes from per-vertex lighting on non-Luminous submeshes
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// routed through the normal mesh pipeline. That path is
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// Phase 2 — see docs/research/2026-04-23-sky-retail-verbatim.md
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// §6 + §10 and the hunt-B finding at 2026-04-23-sky-decompile-hunt-B.md.
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_shader.SetVec4("uTint", Vector4.One);
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EnsureMeshUploaded(gfxObjId);
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if (!_gpuByGfxObj.TryGetValue(gfxObjId, out var subMeshes)) continue;
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@ -202,20 +195,25 @@ public sealed unsafe class SkyRenderer : IDisposable
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{
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// Per-submesh blend mode: sun/moon/stars are Additive
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// (SurfaceType.Additive = 0x10000), clouds are AlphaBlend,
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// sky dome is either Opaque or AlphaBlend depending on the
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// dat. We map Opaque to a passthrough SrcAlpha/InvSrcAlpha
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// with alpha=1, which is equivalent to not blending. This
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// split is architecturally correct (sun's additive blend
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// stops its black texture background from occluding the
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// sky dome behind it) but is NOT how retail does it —
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// retail routes sky meshes through the normal mesh pipe
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// where Surface flags dictate blend state per primitive.
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// See FUN_00508010 (chunk_00500000.c:7535).
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// sky dome is Base1Image (Opaque, mapped to
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// SrcAlpha/InvSrcAlpha for a no-op blend at alpha=1).
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// See FUN_00508010 (chunk_00500000.c:7535) for the retail
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// pattern — retail routes sky meshes through the normal
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// mesh pipeline where Surface flags dictate state.
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if (sub.IsAdditive)
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_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.One);
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else
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_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
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// Per-submesh emissive (Surface.Luminosity FLOAT field —
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// 1.0 for dome + sun + moon, 0.0 for clouds). The vertex
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// shader saturates the lighting math when emissive=1.0 so
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// self-illuminated meshes render at full texture brightness
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// regardless of time of day; emissive=0.0 meshes get the
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// full `ambient + diffuse × sun` tint (producing retail's
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// purple night clouds / warm dusk clouds / pale noon clouds).
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_shader.SetFloat("uEmissive", sub.SurfLuminosity);
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uint tex = _textures.GetOrUpload(sub.SurfaceId);
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_gl.ActiveTexture(TextureUnit.Texture0);
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_gl.BindTexture(TextureTarget.Texture2D, tex);
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@ -403,6 +401,7 @@ public sealed unsafe class SkyRenderer : IDisposable
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IndexCount = sm.Indices.Length,
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SurfaceId = sm.SurfaceId,
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IsAdditive = isAdditive,
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SurfLuminosity = sm.Luminosity,
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};
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}
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@ -428,10 +427,19 @@ public sealed unsafe class SkyRenderer : IDisposable
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public int IndexCount;
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public uint SurfaceId;
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/// <summary>
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/// True if the Surface's flags indicate additive blending should be
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/// used (SurfaceType.Additive OR SurfaceType.Luminous). Computed
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/// once at upload; avoids a per-frame dat lookup.
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/// True if the Surface's <c>SurfaceType.Additive</c> flag (0x10000)
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/// is set. Drives the blend func switch (GL_ONE vs GL_ONE_MINUS_SRC_ALPHA).
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/// Computed once at upload; avoids a per-frame dat lookup.
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/// </summary>
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public bool IsAdditive;
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/// <summary>
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/// <c>Surface.Luminosity</c> float (0..1 — NOT the SurfaceType.Luminous
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/// flag bit). Passed to the sky fragment shader as <c>uEmissive</c>;
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/// when 1.0 it saturates the lighting math so the mesh renders at
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/// full texture brightness (dome, sun). When 0.0 the mesh picks up
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/// the time-of-day ambient+diffuse tint (clouds). See
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/// <c>docs/research/2026-04-23-sky-retail-verbatim.md</c> §6.
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/// </summary>
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public float SurfLuminosity;
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}
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}
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