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D3D12: Fix CONSTANT_ALPHA blend factors collapsing onto constant RGB

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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.
This commit is contained in:
Dipshet
2026-07-15 02:03:35 +02:00
parent c43d2cc74a
commit dfd8b92a5b
2 changed files with 20 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
thirdparty/rexglue-sdk/include/rex/graphics/d3d12/pipeline_cache.h
Vendored
+7 -1
View File
@@ -165,6 +165,12 @@ class PipelineCache {
kBlendFactor,
kInvBlendFactor,
kSrcAlphaSat,
// Constant blend factor using the constant's ALPHA broadcast to RGB (D3D12
// ALPHA_FACTOR / INV_ALPHA_FACTOR). Distinct from kBlendFactor, which uses
// the constant's RGB - the Xenos CONSTANT_ALPHA / ONE_MINUS_CONSTANT_ALPHA
// factors map here, not onto the RGB ones.
kBlendFactorAlpha,
kInvBlendFactorAlpha,
};
// Update PipelineDescription::kVersion if anything is changed!
@@ -219,7 +225,7 @@ class PipelineCache {
PipelineRenderTarget render_targets[xenos::kMaxColorRenderTargets];
static constexpr uint32_t kVersion = 0x20210425;
static constexpr uint32_t kVersion = 0x20260715;
});
REXPACKEDSTRUCT(PipelineStoredDescription, {
thirdparty/rexglue-sdk/src/graphics/d3d12/pipeline_cache.cpp
Vendored
+13 -8
View File
@@ -1509,10 +1509,10 @@ bool PipelineCache::GetCurrentStateDescription(
/* 12 */ PipelineBlendFactor::kBlendFactor,
// ONE_MINUS_CONSTANT_COLOR
/* 13 */ PipelineBlendFactor::kInvBlendFactor,
// CONSTANT_ALPHA
/* 14 */ PipelineBlendFactor::kBlendFactor,
// ONE_MINUS_CONSTANT_ALPHA
/* 15 */ PipelineBlendFactor::kInvBlendFactor,
// CONSTANT_ALPHA - uses the constant's ALPHA, not RGB.
/* 14 */ PipelineBlendFactor::kBlendFactorAlpha,
// ONE_MINUS_CONSTANT_ALPHA - uses 1 - constant ALPHA, not 1 - RGB.
/* 15 */ PipelineBlendFactor::kInvBlendFactorAlpha,
/* 16 */ PipelineBlendFactor::kSrcAlphaSat,
};
// Like kBlendFactorMap, but with color modes changed to alpha. Some
@@ -1534,10 +1534,10 @@ bool PipelineCache::GetCurrentStateDescription(
/* 12 */ PipelineBlendFactor::kBlendFactor,
// ONE_MINUS_CONSTANT_COLOR
/* 13 */ PipelineBlendFactor::kInvBlendFactor,
// CONSTANT_ALPHA
/* 14 */ PipelineBlendFactor::kBlendFactor,
// ONE_MINUS_CONSTANT_ALPHA
/* 15 */ PipelineBlendFactor::kInvBlendFactor,
// CONSTANT_ALPHA - uses the constant's ALPHA, not RGB.
/* 14 */ PipelineBlendFactor::kBlendFactorAlpha,
// ONE_MINUS_CONSTANT_ALPHA - uses 1 - constant ALPHA, not 1 - RGB.
/* 15 */ PipelineBlendFactor::kInvBlendFactorAlpha,
/* 16 */ PipelineBlendFactor::kSrcAlphaSat,
};
// While it's okay to specify fewer render targets in the pipeline state
@@ -2981,6 +2981,11 @@ ID3D12PipelineState* PipelineCache::CreateD3D12Pipeline(
D3D12_BLEND_DEST_ALPHA, D3D12_BLEND_INV_DEST_ALPHA,
D3D12_BLEND_BLEND_FACTOR, D3D12_BLEND_INV_BLEND_FACTOR,
D3D12_BLEND_SRC_ALPHA_SAT,
// kBlendFactorAlpha / kInvBlendFactorAlpha - the constant's alpha
// broadcast to RGB, for the Xenos CONSTANT_ALPHA / ONE_MINUS_CONSTANT_ALPHA
// factors (previously collapsed onto the RGB BLEND_FACTOR, which darkened
// shadows the wrong way - they brightened instead of subtracting).
D3D12_BLEND_ALPHA_FACTOR, D3D12_BLEND_INV_ALPHA_FACTOR,
};
// 8 entries for safety since 3 bits from the guest are passed directly.
static const D3D12_BLEND_OP kBlendOpMap[] = {