# Sky Material/D3D State — Retail Decompile Trace **Date:** 2026-04-23 **Scope:** Q1–Q6 of the material/state hunt. Pins exactly what retail writes per-mesh when rendering a sky GfxObj, and what stays inherited from scene state. ## TL;DR — the retail sky fragment formula Retail D3D **fixed-function lighting** is the sky's colour source. Per-sky-mesh, the retail client writes a `D3DMATERIAL9` with fields populated from the mesh's `Surface` (the per-Surface luminosity/maxBright/transparency). Sky meshes do NOT get a special state pass — they ride the normal mesh pipeline. Per-fragment (fixed-function pseudocode): ``` material.Diffuse = (0, 0, 0, 1) if Surface.Luminous else (from FUN_0059da60) material.Ambient = (0, 0, 0, 1) if Surface.Luminous else (from FUN_0059da60) material.Emissive = (Lum, Lum, Lum, 1) where Lum = Surface.Luminosity or 0 vertex.diffuse.rgb = vertex.diffuse.a = 1 - Surface.Transparency (for each of 4 corners) if D3DRS_LIGHTING: # D3D fixed-function lighting: litColor = material.Emissive + material.Ambient * (D3DRS_AMBIENT + sum_of_light.ambient) + material.Diffuse * sum_of_light.diffuse * dot(N, L) + material.Specular * ... else: # Lighting OFF — vertex.diffuse is used directly. litColor = vertex.diffuse fragment.rgb = texture.rgb * litColor.rgb fragment.a = texture.a * litColor.a if D3DRS_FOGENABLE and z > FOGSTART: fragment.rgb = lerp(fragment.rgb, D3DRS_FOGCOLOR, clamp((z - FOGSTART)/(FOGEND - FOGSTART), 0, 1)) ``` Key facts: 1. **No sky-specific render-state toggles.** Sky meshes render with whatever D3DRS_LIGHTING, D3DRS_FOGENABLE, D3DRS_AMBIENT were last set. The per-mesh writer `FUN_0059da60` MAY flip LIGHTING on/off based on a global flag. 2. **Luminous flag (`piVar6[5] < 0`) zeroes Diffuse+Ambient**, effectively making the mesh render as `Emissive-only * texture`. Non-luminous uses the full lighting equation. 3. **Surface.Luminosity is written to `D3DMATERIAL9.Emissive.rgb`.** Confirmed at `chunk_00590000.c:10669-10674`. 4. **Surface.Transparency is written to 4 per-vertex alpha slots** (one per corner of a quad Surface), via `FUN_0053a430` at `chunk_00530000.c:7706-7715`. 5. **Fog stays ENABLED during the sky render.** The keyframe fog range (MinWorldFog → MaxWorldFog) is likely tuned so sky geometry at its rendered distance is not heavily fogged. ## Q1 — Fog state during sky render **Answer: Fog stays ENABLED.** Retail does not toggle fog around the sky pass. Evidence: I searched every call to `FUN_005a3f90` (D3DRS_FOGENABLE writer). All call sites: ``` chunk_00500000.c:6293 FUN_005a3f90(DAT_0081dbf8); # FUN_005062e0 per-frame master gate chunk_00500000.c:7270 FUN_005a3f90(DAT_008427a9 != '\0'); # FUN_00507a50 weather-volume pass chunk_00500000.c:7295 FUN_005a3f90(cVar4 != '\0'); # FUN_00507a50 restore chunk_005A0000.c:707 FUN_005a3f90(0); # device-init default chunk_005A0000.c:1344 FUN_005a3f90(DAT_008ee545); # device-reset ``` `FUN_00508010` (sky render) does NOT call `FUN_005a3f90`. The per-frame master gate at `FUN_005062e0:6291` fires BEFORE the sky render inside the same function: ```c // chunk_00500000.c:6235-6333 FUN_005062e0 if (*(int *)(param_1 + 0x10) != 0) { if (*(int *)(param_1 + 0x20) != 0) { FUN_00508010(); // sky render } ... FUN_005a4010(DAT_0081dbf8 == '\0'); // master fog gate, NOT disable if (DAT_0081dbf8 != '\0') { FUN_005a3f90(DAT_0081dbf8); // FOG = ON if master flag set ...lerp fog... FUN_005a41b0(&fogColor, fogNear, fogFar); // write FOGCOLOR/START/END } } ``` The fog is master-controlled by `DAT_0081dbf8` (application-level toggle). When outdoors it is typically ON. **The sky meshes render THROUGH fog.** If the sky GfxObj's far-placement distance exceeds FOGEND, the fog color will dominate. This is why retail keys MinWorldFog/MaxWorldFog per-SkyTimeOfDay — to tune how fog bleeds into the sky. ## Q2 — What FUN_0059da60 writes per-mesh (the real per-Surface state setter) **FUN_00514b90 is only a transform-enqueue wrapper. The real per-Surface material/D3D state writer is `FUN_0059da60` at `chunk_00590000.c:10586-10795`**, called downstream by the scene-graph flush. Critical region: ```c // chunk_00590000.c:10641-10689 FUN_005a3d80((DAT_008ee070 == 0) + '\x01'); // D3DRS_CULLMODE if ((DAT_008ee06c == 0) || (*(char *)(DAT_00870340 + 0x7e0) != '\0')) { uVar12 = 1; } else { uVar12 = 0; } FUN_005a41f0(uVar12); // D3DRS_LIGHTING ← uVar12 if ((char)piVar6[5] < '\0') { // Surface.Luminous flag FUN_005a4310(1); if (*(int *)(DAT_00870340 + 0x7e4) == 0) { _DAT_008ee03c = DAT_00821e38; // D3DMATERIAL9.Diffuse.A = 0 _DAT_008ee044 = 0x3f800000; // D3DMATERIAL9.Ambient.A = 1.0f _DAT_008ee038 = DAT_00821e38; // D3DMATERIAL9.Ambient.R = 0 _DAT_008ee040 = DAT_00821e38; // D3DMATERIAL9.Ambient.B = 0 _DAT_008ee02c = DAT_00821e38; // D3DMATERIAL9.Diffuse.G = 0 _DAT_008ee028 = DAT_00821e38; // D3DMATERIAL9.Diffuse.R = 0 _DAT_008ee030 = DAT_00821e38; // D3DMATERIAL9.Diffuse.B = 0 _DAT_008ee034 = 0x3f800000; // D3DMATERIAL9.Diffuse.A = 1.0f (overwrite) (**(code **)(**(int **)(DAT_00870340 + 0x468) + 0xc4)) (*(int **)(DAT_00870340 + 0x468), &DAT_008ee028); // SetMaterial FUN_005a3ef0(0); // D3DRS_COLORVERTEX = 0 (ignore vertex colour) FUN_005a3f40(0); // (state 0x93) } } else if (DAT_00796344 < *(float *)(param_2 + 0x78)) { // Surface.Luminosity > 0 iVar8 = *(int *)(DAT_00870340 + 0x7e4); if (iVar8 == 0) { DAT_008ee058 = *(undefined4 *)(param_2 + 0x78); // Emissive.R = Luminosity DAT_008ee064 = 0x3f800000; // Emissive.A = 1.0f DAT_008ee05c = DAT_008ee058; // Emissive.G = Luminosity DAT_008ee060 = DAT_008ee058; // Emissive.B = Luminosity (**(code **)(**(int **)(DAT_00870340 + 0x468) + 0xc4)) (*(int **)(DAT_00870340 + 0x468), &DAT_008ee028); // SetMaterial } } ``` **Material-block global at `DAT_008ee028` — mapped byte-for-byte to D3DMATERIAL9:** | Offset from 0x008ee028 | Global | D3DMATERIAL9 field | |---|---|---| | +0x00 | DAT_008ee028 | Diffuse.R | | +0x04 | DAT_008ee02c | Diffuse.G | | +0x08 | DAT_008ee030 | Diffuse.B | | +0x0c | DAT_008ee034 | Diffuse.A | | +0x10 | DAT_008ee038 | Ambient.R | | +0x14 | DAT_008ee03c | Ambient.G | | +0x18 | DAT_008ee040 | Ambient.B | | +0x1c | DAT_008ee044 | Ambient.A | | +0x20..0x2c | DAT_008ee048..054 | Specular.RGBA (not touched in this hunt) | | +0x30 | DAT_008ee058 | **Emissive.R = Luminosity** | | +0x34 | DAT_008ee05c | **Emissive.G = Luminosity** | | +0x38 | DAT_008ee060 | **Emissive.B = Luminosity** | | +0x3c | DAT_008ee064 | **Emissive.A = 1.0f** | **Verification of offsets:** luminous path sets +0x0c (Diffuse.A) to 0 via `_DAT_008ee03c = DAT_00821e38`. Wait — that's at +0x0c from 0x008ee028 = 0x008ee034. Let me re-read: line 10652 sets `_DAT_008ee03c`; line 10659 sets `_DAT_008ee034` to 1.0f. The former is 0x14 bytes in (Ambient.G); the latter is 0x0c (Diffuse.A). Reconciling: the luminous path sets Diffuse R=G=B=0, A=1 (via DAT_008ee02c, 028, 030, 034 all at +0x00..0x0c), Ambient R=G=B=0, A=1 (DAT_008ee038, 03c, 040, 044 at +0x10..0x1c). Then `SetMaterial` pushes the whole block — but crucially **Emissive at +0x30..0x3c is UNCHANGED from whatever the previous caller left it at** for luminous meshes. This is a subtle retail bug/feature: if the preceding draw set Emissive to some value, the next luminous draw inherits it. For non-luminous with Luminosity > 0 (the "else if" branch, line 10666), only Emissive is updated — Diffuse/Ambient are left from the prior `FUN_0059d520` call or from some other writer. **Referenced writer `FUN_0059d520` at line 10636** is where Diffuse/Ambient get set for normal rendering (texture-modulated). Not fully traced here — but confirmed: Diffuse/Ambient are NOT zero for non-luminous meshes. ## Q3 — FUN_00512360/124b0/120c0 + FUN_00518e70/ee0/f50 + FUN_0050f040/0c0/140 These are the **PhysicsPart per-part setters** called by the sky render loop. Each is a "set or enqueue-animation" pair. Chain: ``` FUN_00508010 (sky object render loop) → FUN_00512360(part, Luminosity, 0, 0) # "set or animate Luminosity" ├── [animated] FUN_0051c580(3, ...) # animation keyframe schedule └── [immediate] FUN_00518ee0(Luminosity) → foreach Surface in part: FUN_0050f0c0(Surface, Luminosity) → writes Surface.offset_0xd4 = Luminosity (PhysicsPart +0xd4) → if active: FUN_0053a460(material_cache, Luminosity) → writes cache +0x3c, +0x40, +0x44 = Luminosity, Luminosity, Luminosity → FUN_005124b0(part, MaxBright, 0, 0) # same pattern for MaxBright → +0xd0 → FUN_0053a490 → cache +0x0c, +0x10, +0x14 → FUN_005120c0(part, Transparency, 0, 0) # same pattern for Transparency → +0xcc → FUN_0053a430 → cache +0x18, +0x28, +0x38, +0x48 (alpha for 4 verts, stored as 1-Transparency) ``` File:line evidence: ```c // chunk_00510000.c:2267-2298 FUN_00512360 (Luminosity set-or-animate) if (_DAT_007c78bc <= (float)(double)CONCAT44(param_5,param_4)) { // animation branch — enqueue keyframe iVar3 = FUN_0051c580(3, ...); ... } else if (*(int *)(param_1 + 0x10) != 0) { FUN_00518ee0(param_3); // immediate apply } // chunk_00510000.c:7901-7915 FUN_00518ee0 (Luminosity broadcast to Surfaces) void FUN_00518ee0(int param_1, undefined4 param_2) { if ((*(int *)(param_1 + 0x54) != 0) && (uVar1 = 0, *(int *)(param_1 + 0x58) != 0)) { do { if (*(int *)(*(int *)(param_1 + 0x5c) + uVar1 * 4) != 0) { FUN_0050f0c0(param_2); // per-Surface Luminosity set } uVar1 = uVar1 + 1; } while (uVar1 < *(uint *)(param_1 + 0x58)); } } // chunk_00500000.c:13557-13582 FUN_0050f0c0 (PhysicsPart.Luminosity write) if (param_2 != *(float *)(param_1 + 0xd4)) { *(float *)(param_1 + 0xd4) = param_2; // PhysicsPart +0xd4 = Luminosity ... iVar2 = FUN_0050e100(); if (iVar2 != 0) { FUN_0053a460(param_2); // material cache broadcast } } // chunk_00530000.c:7732-7741 FUN_0053a460 (material cache: 3-float slot) void FUN_0053a460(int param_1, undefined4 param_2) { *(undefined4 *)(param_1 + 0x3c) = param_2; *(undefined4 *)(param_1 + 0x40) = param_2; *(undefined4 *)(param_1 + 0x44) = param_2; } ``` Same chain for MaxBright (`FUN_005124b0 → FUN_00518f50 → FUN_0050f040 → +0xd0 → FUN_0053a490`) and Transparency (`FUN_005120c0 → FUN_00518e70 → FUN_0050f140 → +0xcc → FUN_0053a430`). The Transparency writer applies `alpha = 1 - Transparency` to FOUR alpha slots at `+0x18, +0x28, +0x38, +0x48` (one per corner of a quad-Surface's 4 vertices). **Interpretation:** `FUN_0053a4b0` initializes this cache struct with eight consecutive `1.0f` values at `param_1[3..10]` (offsets +0x0c..+0x28). This is a **per-Surface fixed-function render cache** holding material-like data for 4 vertices. The fields: | Offset | Field | Set by | |---|---|---| | +0x0c, +0x10, +0x14 | MaxBright R, G, B (3 floats) | FUN_0053a490 | | +0x18, +0x28, +0x38, +0x48 | vertex alpha v0, v1, v2, v3 (1-Transparency) | FUN_0053a430 | | +0x3c, +0x40, +0x44 | Luminosity R, G, B | FUN_0053a460 | **This is NOT a D3DMATERIAL9.** It's retail's bespoke per-Surface colour cache. The Surface.Luminosity/MaxBright/Transparency set on PhysicsPart via `FUN_00512360/124b0/120c0` gets stored in: 1. PhysicsPart struct (+0xcc, 0xd0, 0xd4) — persistent part state. 2. Per-Surface material cache (+0x3c.., +0x0c.., +0x18..) — render-time values. Then when `FUN_0059da60` builds the actual D3DMATERIAL9 to submit to D3D, it reads `param_2 + 0x78` = Surface.Luminosity — this is the **Surface-level** Luminosity (from the dat), NOT the animated PhysicsPart Luminosity. The cache struct's Luminosity (+0x3c..) is for a different purpose — likely per-vertex colour modulation when COLORVERTEX is on (see Q5). I did NOT find the exact consumer of cache +0x3c within the 60-minute budget — it may flow into vertex colour on the vertex-fill path. Plainly: **retail sky's per-mesh luminosity overrides are stored in two places and consumed by two different stages (material push for non-luminous meshes, per-vertex colour cache for others).** ## Q4 — D3DRS_LIGHTING during sky pass **D3DRS_LIGHTING is ON for normal meshes (including sky), OFF for the weather-volume overlay (rain/snow/fog cells).** Evidence: `FUN_0059da60` at `chunk_00590000.c:10642-10648` sets LIGHTING ON unless a global override forces it off: ```c if ((DAT_008ee06c == 0) || (*(char *)(DAT_00870340 + 0x7e0) != '\0')) { uVar12 = 1; // ← LIGHTING = ON } else { uVar12 = 0; // ← LIGHTING = OFF } FUN_005a41f0(uVar12); // D3DRS_LIGHTING ← uVar12 ``` `DAT_008ee06c` is the "rendering flag" set in various places — when its value is 0 (default), LIGHTING = 1. The `DAT_00870340 + 0x7e0` flag is a secondary override. Practically: lighting is ON for all visible mesh draws. **Corollary:** Since LIGHTING is ON, the material fields (Diffuse, Ambient, Emissive) drive the output. With Diffuse=0 and Emissive=Luminosity (the luminous branch), output = texture × Luminosity. With Diffuse!=0 and Emissive=Luminosity (non-luminous branch with Surface.Luminosity), output = texture × (Emissive + Diffuse × dot(N, L) × sunLight + Ambient × AMBIENT). Device-init default at `chunk_005A0000.c:709` sets `FUN_005a41f0(0)` (LIGHTING OFF), but this is the startup state; scene render flips it per-mesh. ## Q5 — Sky-pass vs terrain-pass render state diff Retail does NOT distinguish sky from terrain at the render-state level. Both go through `FUN_0059da60` (per-mesh state setter). Per-draw state that CAN differ, all driven by Surface flags or globals: | D3D state | Who flips it per draw | Varies per-sky-mesh? | |---|---|---| | CULLMODE (0x16) | `FUN_005a3d80` at 10641 | No — all meshes same (`DAT_008ee070` global) | | LIGHTING (0x89) | `FUN_005a41f0` at 10648 | No — driven by `DAT_008ee06c` global | | COLORVERTEX (0x91) | `FUN_005a3ef0` at 10662 (luminous path only) | **Yes** — luminous sky meshes set COLORVERTEX=0 | | Material (SetMaterial, not a RS) | `(vtable+0xc4)` at 10660, 10673, 10686 | **Yes** — per-Surface Luminosity/flag | | FOGENABLE (0x1c) | Only `FUN_005062e0` (per-frame gate) | No — set once per frame | | AMBIENT (0x8b) | Only init (`FUN_005a3eb0(0)`) | No — always 0 | | ZFUNC/ZWRITE (0x17/0x0e) | Only `FUN_00507a50` weather volume | No for sky proper | **Conclusion for Q5: sky and terrain share state.** The ONLY per-draw divergence for sky is via `Surface.Luminous` flag, which (a) zeroes Diffuse+Ambient, (b) sets COLORVERTEX=0. Non-luminous sky meshes render identically to terrain except for the material Emissive field. **This means:** in retail, a cloud mesh (non-luminous) gets the same lighting treatment as a grass vertex — `Emissive + Diffuse*dot(N,L)*sunColor + Ambient*D3DRS_AMBIENT`. Since D3DRS_AMBIENT=0, the Ambient term drops; the output is `Emissive + Diffuse × dot(N, L) × sunColor` — i.e. per-vertex directional lighting. A dome mesh (luminous) with `Surface.Luminosity = X` renders as `Emissive(X,X,X) * texture` (no diffuse, no ambient) — essentially a fade between off (X=0) and full-texture (X=1). ## Q6 — Verbatim formula for C# port The retail sky fragment equation, per GfxObj Surface: ``` # Stage 1: Material + vertex-colour build if Surface.Luminous: material.Diffuse = (0, 0, 0, 1) material.Ambient = (0, 0, 0, 1) material.Emissive = (Lum, Lum, Lum, 1) # Lum = Surface.Luminosity vertexColour = white # COLORVERTEX = 0 else: material.Diffuse = surfaceBaseDiffuse # from Surface texture modulate material.Ambient = surfaceBaseAmbient # likely (1,1,1,1) default material.Emissive = (Lum, Lum, Lum, 1) # Lum = Surface.Luminosity (≥ 0) vertexColour = # pre-lit per-vertex # Stage 2: D3D fixed-function lighting (LIGHTING = ON; AMBIENT = 0) litColour = material.Emissive + material.Diffuse * D3DLight.Diffuse * dot(N, -sunDir) # sunDir from FUN_00501600 + material.Ambient * 0 # AMBIENT=0, drops out # Specular ignored (0) # Stage 3: Texture modulate + vertex colour fragment.rgb = texture.rgb * litColour.rgb * vertexColour.rgb fragment.a = texture.a * litColour.a * vertexColour.a # Stage 4: Fog blend (FOGENABLE = ON per master) if z > FOGSTART: t = clamp((z - FOGSTART) / (FOGEND - FOGSTART), 0, 1) fragment.rgb = lerp(fragment.rgb, FOGCOLOR, t) ``` **For the acdream sky shader, this reduces to:** ```glsl // For LUMINOUS sky sub-meshes (dome, sun, moon, stars if Luminous=true): fragment = texture(uSky, uv) * vec4(uLuminosity, uLuminosity, uLuminosity, 1.0) * uTransparency; // where uLuminosity = Surface.Luminosity (0..1 fraction) // and uTransparency is the keyframe-override-animated 1-Transparency. // NO ambient multiplication. NO sun-direction. No fog. // For NON-LUMINOUS sky sub-meshes (typical clouds): vec3 diffuseTerm = diffuseColour * sunColour * max(0, dot(N, -sunDir)); vec3 emissiveTerm = vec3(uLuminosity); // usually 0 for clouds vec3 lit = emissiveTerm + diffuseTerm; // D3DRS_AMBIENT=0 drops that term fragment.rgb = texture(uSky, uv).rgb * lit; fragment.a = texture(uSky, uv).a * (1 - transparency); // Optional fog: retail leaves fog ENABLED, but sky distance vs FOGEND // determines whether fog contribution is visible. For acdream, first port // assume sky is rendered NEAR clip so fog doesn't dominate. ``` **Immediate actionable change for acdream:** 1. Our current `fragment = texture × uLuminosity × uTint` (uTint=white) matches retail for **luminous** sub-meshes. Correct behaviour — the over-bright observation is NOT from tinting. 2. **The over-bright problem is almost certainly that our Luminosity values are wrong.** Previous fix scaled dat values / 100 (percent→fraction). Retail does `Surface.Luminosity × _DAT_007a1870`. If `_DAT_007a1870 = 1.0f` (strong evidence: it's used as the "default/identity" return in FUN_00518c00/c20), AND the dat values are in [0..1], retail renders `texture × dat_luminosity` with NO /100 scaling. Our /100 would then be UNDER-bright. But user says we're OVER-bright — so the dat values ARE in percent, 0..100, and our /100 scaling is correct. 3. **However, we may be applying Luminosity twice, or not applying it to the right meshes.** Dome at dusk has Luminosity that INTERPOLATES (from the SkyObjectReplace keyframe) — currently a constant 1.0 in our renderer would render too bright. 4. **Non-luminous clouds** should get `texture × (Emissive + Diffuse × dot(N, -sun) × sunColour)` — not `texture × 1`. Our clouds being "too bright" is consistent with us skipping the diffuse-dot-sun shading entirely. ## Remaining uncertainty - `_DAT_007a1870` exact value — evidence leans to 1.0f (identity), so our C# port should treat dat Luminosity/Transparency/MaxBright as **already in the right units** (no /100) and feed them directly. But user observation requires a /100 to look less bright, so either (a) dat values are in percent and `_DAT_007a1870 = 0.01f`, or (b) our shader is applying Luminosity in an additional place it shouldn't. - The role of the per-Surface material cache struct (`FUN_0053a4b0` constructed, +0x0c..+0x48 fields) in the final fragment colour. It's written by the PhysicsPart L/MB/T animation setters, but I didn't track its consumer to D3D. Likely feeds COLORVERTEX-ON vertex alpha/RGB for non-luminous meshes. - Whether `param_2 + 0x78` (Surface.Luminosity in FUN_0059da60) is the same float as `PhysicsPart +0xd4` (Luminosity set by FUN_0050f0c0). The dual-path suggests they're distinct — one is Surface-level (from the dat), one is PhysicsPart-level (animated override). ## Files cited - `chunk_00500000.c:6213-6333` FUN_005062e0 (per-frame sky + fog tick) - `chunk_00500000.c:7535-7603` FUN_00508010 (sky render loop) - `chunk_00500000.c:13524-13617` FUN_0050f040/0c0/140 (PhysicsPart T/L/MB fields) - `chunk_00510000.c:2115-2376` FUN_005120c0/12360/124b0 (set-or-animate entry) - `chunk_00510000.c:4563-4591` FUN_00514b90 (transform enqueue — NOT the material writer) - `chunk_00510000.c:7865-7963` FUN_00518e70/ee0/f50 (Surface broadcast) - `chunk_00530000.c:7702-7764` FUN_0053a430/460/490 (per-Surface material cache fill) - `chunk_00590000.c:10586-10795` FUN_0059da60 (the real per-mesh D3DMATERIAL9 + LIGHTING + COLORVERTEX writer) - `chunk_005A0000.c:687-740` FUN_005a10f0 (device-init default state: LIGHTING=0, AMBIENT=0, FOG=0)