Dipshet dfd8b92a5b D3D12: Fix CONSTANT_ALPHA blend factors collapsing onto constant RGB ...

The D3D12 PipelineBlendFactor enum had no constant-alpha entry, so the Xenos
CONSTANT_ALPHA and ONE_MINUS_CONSTANT_ALPHA blend factors (14, 15) were mapped
onto the constant-COLOR kBlendFactor / kInvBlendFactor - i.e. D3D12 BLEND_FACTOR
/ INV_BLEND_FACTOR, which use the blend constant's RGB rather than its alpha.

Aircraft ground shadow blends with dst = ONE_MINUS_CONSTANT_ALPHA and aSTANT_ALPHA blend factors collapsing onto
blend constant of (0.03, 0.04, 0.04, 0.30): it wants 1 - 0.30 = 0.70 (scale the
background down -> darken), but got 1 - (0.03,0.04,0.04) ~= 0.97 (barely scaled)
with the white source added on top, so the shadow BRIGHTENED instead of
darkening - the "white shadow" bug. Vulkan has the distinct
ONE_MINUS_CONSTANT_ALPHA factor and renders it correctly.

Add kBlendFactorAlpha / kInvBlendFactorAlpha to the enum, route factors 14/15 to
them in both the colour and alpha maps, and map them to D3D12 ALPHA_FACTOR /
INV_ALPHA_FACTOR. Verified fixed on both the RTV and ROV render-target paths.

2026-07-15 02:03:35 +02:00

..

rexglue-sdk

D3D12: Fix CONSTANT_ALPHA blend factors collapsing onto constant RGB

2026-07-15 02:03:35 +02:00