G-buffer shading classes

The material shader packs both a normal and a shading class into the G-buffer. The lighting pass uses the class to interpret other channels, so the same output component does not always mean metalness or emission. Observed · material writers and deferred consumer

Normals are octahedrally encoded. The two projected components are quantized to nine bits; their low eight bits occupy o1.x/y, while high bits and a normal sign share o1.z with the class. Observed · writer and consumer disassembly

Output	Class 1, ordinary surface	Classes 3–5, terrain/vegetation family	Confidence
o0.rgb	Base colour	Base colour	Observed
o0.w	Perceptual roughness	Perceptual roughness	Observed
o1.xyz	Packed world normal and class	Packed world normal and class	Observed
o1.w	Metalness	Ambient occlusion	Observed
o2.xy	Motion vector	Motion vector	Observed
o2.z	Emissive scalar, commonly exposure-divided	Specular occlusion	Observed
o2.w	Pass-dependent alpha	Translucency	Observed
o3.x	AO	Family-specific additional output	Observed

Tex1’s forward shader establishes the roughness convention: it clamps the stored roughness to at least .045 and squares it to obtain GGX alpha. Metalness drives F0=lerp(.04,albedo,metalness) and diffuse albedo*(1-metalness). This discriminates roughness from the older SpecGloss label. Observed · forward program arithmetic

Template	Class	Checked class-writing permutations	Confidence
Tex1_TerrainBlend	3	20	Proven · every class-writing permutation and control-flow path
Clutters_Grass	4	8	Proven · every class-writing permutation and control-flow path
Tex1_Leaves	5	32	Proven · every class-writing permutation and control-flow path
Bark	5	8	Proven · every class-writing permutation and control-flow path
Tex1_Rocks	5	8	Proven · every class-writing permutation and control-flow path

These programs do not write class 1; the deferred non-metal branch uses F0 .04 rather than reading their o1.w as metalness. TerrainBlend’s class-writing permutations never read its material property labelled Metalness. Other permutations with UAV atomics belong to the fragment-recording pass and do not establish an alternative shading class for an ordinary G-buffer draw. Observed · all listed class writers and consumer

In those five templates the other o1-writing permutations (16, 8, 8, 2 and 2 of them) increment a structured u6 counter with imm_atomic_iadd and store a record to u7; their o0 is cb1[85] or a t70 record, o1.xyz a normal and o1.w zero, with no class byte. Observed · every o1-writing permutation of the five templates

The class literal

The class is a literal in the program, not a value it computes. The shader builds o1.z’s byte by inserting the normal’s sign at bit 0 and adding its two high bits with weights 2 and 4. It then adds the literal 8 for class 1, 24 for class 3 or 32 for class 4, and writes the byte divided by 255. The class is therefore byte >> 3, and no normal can change it. Observed · the packing code of the saved permutations below The water atlases’ bytes 48 and 80 (classes 6 and 10, on Water surfaces) follow the same rule. Inferred

Templates	Class	Checked permutation	Confidence
Tex1_SkinningSupported, Tex1_TeamColoured, Tex2, Tex2_TintBFromShaderConstants, Tex2_Graffiti_Mode, Grounds, Road, Hero_Ice, IceBrick, Tex1_UniqueNormalGradient, Tex1_Screen, Screens, Screens_Simple, SHD_UNLIT_UndergroundBox, Tex1_FakeRiver	1	ps_400000 of each	Observed · one permutation per template
Decals1_Graffiti, Tex1_Graffiti_Mode_DecalFX	1	the cut-out permutations ps_404004 and ps_404000	Observed · one permutation per template
Outskirt	3	ps_400000	Observed · one permutation
SHD_Nat_Veg_Grass_AO	4	ps_400000	Observed · one permutation

In these, class 1 has o1.w metalness, o2.z the albedo-scaled emission and o3.x the occlusion of all light. Outskirt writes o1.w = 1 (its AO) and o2.zw = (1, 0), and Grass_AO o1.w = 1, o2.z = .2 and o2.w = 0; neither writes metalness or emission. Observed · the same permutations A valid class does not mean that every input of these programs is a material value: the video and state branches of the screen templates, for example, read run-time state. Observed

What does the fragment-recording pass feed?

Its target and UAV writes are established, but the full downstream use is not. Unknown