VM2's live cdb read against the PDB-paired retail client (GUID
9e847e2f-777c-4bd9-886c-22256bb87f32) proved
m_caps.bCanDoSinglePassDetailing = 1 and trysinglepass = 1 on real hardware,
so D3DPolyRender::RenderMeshSubset (0x0059ca10) never falls back to the
two-pass framebuffer blend the earlier #226 port reproduced. Every loaded
CGfxObj sets use_built_mesh = 1 (CGfxObj::InitLoad 0x005346b0), so buildings
and EnvCells always take the single-pass texture-stage combine set up in
D3DPolyRender::SetSurface (0x0059c4d0):
result = lerp(base * diffuse, detail.rgb, detail.a * diffuse.a)
RenderMeshSubset lights opaque built-mesh subsets with
tmpmaterial.Diffuse.a = 1, so on the live Dereth category texture
0x06006D58 (mean rgb 0.165, mean alpha 0.132) the combine works out to
~0.868 * base + 0.022 — a mild darkening, the opposite sign of the fallback
DstColor blend's brightening.
Also removes the invented 10 m / 50 m distance fade. Retail's
ACRender::get_alpha_for_z (0x006b6230) is only evaluated in
D3DPolyRender::DrawPolyInternal (0x0059d7c0, the immediate-polygon path)
and only when the static noFadeDetail (0x00820e38, initialised to 1) is 0 —
unreachable for built meshes. Attenuation is the sampler's linear mip chain
converging to the texture mean, not a scripted ramp.
Changes:
- mesh_detail.vert/.frag: drop vDetailFade and its distance term; add
vDetailOpacity mirroring mesh_modern.vert's InstanceAlphaBuf (binding 7)
read, and output detail.rgb with alpha = detail.a * vDetailOpacity under
the corrected pipeline blend.
- VulkanViewportMapping.BlendFactorsOf / GpuEnums.GpuBlendMode.RetailDetail:
SrcAlpha + OneMinusSrcAlpha instead of DstColor + OneMinusSrcAlpha.
- RetailDetailTextureContract: replaced the distance-fade constants and
FramebufferFactor with Expected(base, detail, opacity) and IsNeutral,
matching the lerp; contract tests cover zero-alpha/zero-opacity no-ops,
the measured darkening on the live category texture, and full-alpha
replacement.
- Regenerated mesh_detail's committed SPIR-V and the shader manifest
(tools/compile-shaders.ps1); no other shader pair changed.
- Docs: #226's pseudocode note, the docs/ISSUES.md #226 entry, and the
retired TS-52 divergence-register row corrected from the two-pass
DESTCOLOR description to the single-pass path and the darkening
expectation, each citing the VM2 cdb note.
Verified: dotnet build AcDream.slnx -c Release (0 warnings, 0 errors);
dotnet test on AcDream.App.Tests and AcDream.Core.Tests (Release, hermetic
lanes) both green.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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