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sky(phase-1): revert speculative tint, add ACDREAM_DUMP_SKY diagnostic

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The uncommitted uTint=AmbientColor-for-alpha-submeshes experiment (from
the 2026-04-22 inference) dimmed the sky dome's baked gradient — a
user-verified visual regression. Reverting to the eeae83a baseline
(uTint=Vector4.One for every submesh) while we execute the proper
retail-verbatim port.

Research: three parallel decompile-hunt agents landed verifying
retail's ground-truth sky pipeline for the first time (prior audits
searched for stripped symbol names; the trail opened via the Region
dat-type-index 0x1c registration at chunk_00410000.c:12952). Key
retail functions now mapped in chunk_00500000.c:1097-7535:
  - FUN_00501530: keyframe bracket-picker (with 1.0f wrap denominator)
  - FUN_00501600: sun+ambient interpolator (sunVec = DirBright ×
                  (sin yaw·cos pit, cos yaw·cos pit, sin pit))
  - FUN_00501860: fog interpolator
  - FUN_00502820: SkyDesc::Unpack (2 doubles + DayGroup list)
  - FUN_00502a10: build per-frame sky-object table
  - FUN_00505f30: apply light state + per-cell AdjustPlanes relight
  - FUN_005062e0: per-frame sky tick (throttled by LightTickSize)
  - FUN_00508010: sky-object render loop (enqueues through the NORMAL
                  mesh pipeline via FUN_00514b90 — not a bespoke path)

Surprise findings:
  - D3DRS_AMBIENT is set to 0 once at init and NEVER changes per-frame
    (chunk_005A0000.c). The r12-inferred "clouds = texture × D3DRS_
    AMBIENT" formula is falsified. Retail instead routes keyframe
    AmbColor through per-vertex lighting on non-Luminous sky meshes
    via _DAT_008682bc/c0/c4.
  - Retail does NOT anchor the sky to the camera or use a separate
    sky projection. Sky meshes live in world space and follow the
    camera via scene-graph parent.
  - FUN_00532440 (AdjustPlanes) re-lights every terrain cell on every
    keyframe tick — the "terrain follows the sky" effect we don't yet
    reproduce.

Phase 1 code change (this commit):
  - src/AcDream.App/Rendering/Sky/SkyRenderer.cs: revert uTint to white
    for all submeshes (the per-submesh blend split stays — sun gets
    additive, clouds get alpha). Keep the `keyframe` parameter in the
    signature for Phase 2 readiness. Comments now cite the retail
    functions and reference docs instead of the (disproven) r12 formula.
  - src/AcDream.Core/World/SkyDescLoader.cs: ACDREAM_DUMP_SKY=1 logs
    the entire Region SkyDesc on load — DayGroups, SkyObjects, every
    SkyTimeOfDay keyframe, and every SkyObjectReplace with RAW pre-/100
    Transparent/Luminosity/MaxBright values so we can settle the unit
    question empirically.
  - src/AcDream.App/Rendering/Sky/SkyRenderer.cs: ACDREAM_DUMP_SKY=1
    additionally logs each sky GfxObj's Surfaces and their SurfaceType
    flags on first load, so we can identify which meshes carry the
    Luminous bit (dome? sun? moon? stars?) vs which are lit.
  - src/AcDream.App/Rendering/GameWindow.cs: passes the interpolated
    keyframe to the sky renderer (kept — needed for Phase 2).

Research docs (pushed as part of this commit):
  - docs/research/2026-04-23-sky-retail-verbatim.md: full synthesis
    with retail function map, struct layouts, globals, pseudocode, and
    a 4-phase port plan.
  - docs/research/2026-04-23-sky-decompile-hunt-{A,B,C}.md: raw hunt
    outputs.
  - docs/research/2026-04-23-sky-references-crossref.md: WorldBuilder/
    ACE/ACViewer/holtburger/Chorizite coverage.
  - docs/research/2026-04-23-sky-dat-schema.md: full dat schema + unit
    analysis.
  - docs/research/2026-04-22-sky-lighting-decompile.md: prior agent's
    (superseded) inference — kept for provenance.

Phase 2 will port Surface.Luminous-flag-aware per-vertex lighting for
sky submeshes once the dump resolves the open questions (Luminous-flag
distribution per Dereth sky mesh; _DAT_007a1870 scale constant value).

Build + 717 tests green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-04-23 18:06:52 +02:00
parent eeae83a14e
commit 58afd4850f
10 changed files with 2854 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

2
src/AcDream.App/Rendering/GameWindow.cs
View file

@ -3612,7 +3612,7 @@ public sealed class GameWindow : IDisposable
if (!cameraInsideCell)
{
_skyRenderer?.Render(camera, camPos, (float)WorldTime.DayFraction,
_loadedSkyDesc?.DefaultDayGroup);
_loadedSkyDesc?.DefaultDayGroup, kf);
}
_terrain?.Draw(camera, frustum, neverCullLandblockId: playerLb);

100
src/AcDream.App/Rendering/Sky/SkyRenderer.cs
View file

@ -72,12 +72,28 @@ public sealed unsafe class SkyRenderer : IDisposable
/// <summary>
/// Draw the sky for this frame. Called FIRST in the render loop —
/// terrain / meshes / debug lines / overlay land on top.
///
/// <para>
/// <paramref name="keyframe"/> is accepted for forward-compatibility
/// with the retail-verbatim per-vertex lighting path (see
/// <c>docs/research/2026-04-23-sky-retail-verbatim.md</c>). It is
/// NOT currently consumed by the shader — sky meshes render at
/// <c>uTint = white</c> (texture passthrough). A prior experiment
/// multiplied alpha-blended submeshes by <c>keyframe.AmbientColor</c>
/// to tint clouds; this dimmed the sky dome's baked gradient
/// (user-verified regression) and was reverted. Retail actually
/// routes sky meshes through the normal mesh pipeline with
/// Surface.Type.Luminous controlling lit-vs-unlit per submesh; the
/// correct port lives downstream in Phase 2 once we have the live
/// Surface flags dumped.
/// </para>
/// </summary>
public void Render(
ICamera camera,
Vector3 cameraWorldPos,
float dayFraction,
DayGroupData? group)
DayGroupData? group,
SkyKeyframe keyframe)
{
if (group is null || group.SkyObjects.Count == 0) return;
@ -167,6 +183,16 @@ public sealed unsafe class SkyRenderer : IDisposable
_shader.SetVec2("uUvScroll", new Vector2(uOffset, vOffset));
_shader.SetFloat("uTransparency", transparent);
_shader.SetFloat("uLuminosity", luminosity);
// uTint stays white: retail renders sky meshes as texture
// passthrough (the gradient lives in the mesh texture, not in
// a shader ambient multiply). D3DRS_AMBIENT is set to 0 once
// at retail device-init and never changes per-frame — verified
// in chunk_005A0000.c (state 0x8b = 139, only external caller
// is the default-reset at line 704). The "cloud tint" effect
// comes from per-vertex lighting on non-Luminous submeshes
// routed through the normal mesh pipeline. That path is
// Phase 2 — see docs/research/2026-04-23-sky-retail-verbatim.md
// §6 + §10 and the hunt-B finding at 2026-04-23-sky-decompile-hunt-B.md.
_shader.SetVec4("uTint", Vector4.One);
EnsureMeshUploaded(gfxObjId);
@ -174,16 +200,21 @@ public sealed unsafe class SkyRenderer : IDisposable
foreach (var sub in subMeshes)
{
// Per-submesh blend mode: sun/moon/stars are usually
// Additive or Luminous, clouds are AlphaBlend, star dome
// backing is Opaque (but we still need blend-enabled to
// avoid a hard seam against the sky gradient behind it —
// we map Opaque to a passthrough SrcAlpha/OneMinusSrcAlpha
// with alpha=1, which is equivalent to not blending).
// Per-submesh blend mode: sun/moon/stars are Additive
// (SurfaceType.Additive = 0x10000), clouds are AlphaBlend,
// sky dome is either Opaque or AlphaBlend depending on the
// dat. We map Opaque to a passthrough SrcAlpha/InvSrcAlpha
// with alpha=1, which is equivalent to not blending. This
// split is architecturally correct (sun's additive blend
// stops its black texture background from occluding the
// sky dome behind it) but is NOT how retail does it —
// retail routes sky meshes through the normal mesh pipe
// where Surface flags dictate blend state per primitive.
// See FUN_00508010 (chunk_00500000.c:7535).
if (sub.IsAdditive)
_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.One); // additive
_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.One);
else
_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha); // alpha
_gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
uint tex = _textures.GetOrUpload(sub.SurfaceId);
_gl.ActiveTexture(TextureUnit.Texture0);
@ -267,12 +298,63 @@ public sealed unsafe class SkyRenderer : IDisposable
return;
}
// Phase 1 diagnostic: dump Surface.Type flags on every sky GfxObj
// once, so we can determine which submeshes carry Luminous (0x40)
// vs plain-lit. This settles the retail "cloud tint = per-vertex
// lighting on non-Luminous meshes" hypothesis — see
// docs/research/2026-04-23-sky-retail-verbatim.md §6.
if (System.Environment.GetEnvironmentVariable("ACDREAM_DUMP_SKY") == "1")
DumpGfxObjSurfaces(gfxObjId, gfx, subMeshes);
var gpuList = new List<SubMeshGpu>(subMeshes.Count);
foreach (var sm in subMeshes)
gpuList.Add(UploadSubMesh(sm));
_gpuByGfxObj[gfxObjId] = gpuList;
}
/// <summary>
/// Log each surface's raw flag bits and the derived
/// <see cref="TranslucencyKind"/>. Called once per GfxObj when
/// <c>ACDREAM_DUMP_SKY=1</c>. Output format is grep-friendly so
/// we can pipe the launch log through <c>| grep sky-dump</c> and
/// recover a complete picture of the Dereth sky without re-running.
/// </summary>
private void DumpGfxObjSurfaces(
uint gfxObjId,
GfxObj gfx,
System.Collections.Generic.IReadOnlyList<GfxObjSubMesh> subMeshes)
{
Console.WriteLine(
$"[sky-dump] GfxObj 0x{gfxObjId:X8} Surfaces.Count={gfx.Surfaces.Count} Polygons.Count={gfx.Polygons.Count} SubMeshes.Count={subMeshes.Count}");
for (int i = 0; i < gfx.Surfaces.Count; i++)
{
uint surfaceId = (uint)gfx.Surfaces[i];
DatReaderWriter.DBObjs.Surface? surface = null;
try { surface = _dats.Get<DatReaderWriter.DBObjs.Surface>(surfaceId); }
catch { surface = null; }
if (surface is null)
{
Console.WriteLine($"[sky-dump] Surface[{i}] 0x{surfaceId:X8} -- (dat read failed)");
continue;
}
// SurfaceType is a flag enum — `ToString()` gives the
// comma-joined names (e.g. "Base1Image, Additive").
uint rawType = (uint)surface.Type;
string names = surface.Type.ToString();
uint origTex = surface.OrigTextureId?.DataId ?? 0u;
var trans = TranslucencyKindExtensions.FromSurfaceType(surface.Type);
// Surface's own Luminosity (0..1 fraction per test fixture —
// different from SkyObjectReplace.Luminosity which lives in the keyframe).
Console.WriteLine(
$"[sky-dump] Surface[{i}] 0x{surfaceId:X8} Type=0x{rawType:X8} ({names}) " +
$"OrigTexture=0x{origTex:X8} Translucency={trans} " +
$"SurfLuminosity={surface.Luminosity:F4} SurfTranslucency={surface.Translucency:F4}");
}
}
private SubMeshGpu UploadSubMesh(GfxObjSubMesh sm)
{
uint vao = _gl.GenVertexArray();