From 53061c63feef3b6ea6d455f6c012195a0e57f226 Mon Sep 17 00:00:00 2001
From: goldislead <69987043+goldislead@users.noreply.github.com>
Date: Fri, 7 Aug 2026 19:37:00 -0700
Subject: [PATCH] [Vulkan] Use dedicated alpha blend factor map for alpha
 srcb/dest blend

Matches D3D12.

Co-authored-by: Herman S. <429230+has207@users.noreply.github.com>
---
 src/xenia/gpu/vulkan/vulkan_pipeline_cache.cc | 26 +++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/xenia/gpu/vulkan/vulkan_pipeline_cache.cc b/src/xenia/gpu/vulkan/vulkan_pipeline_cache.cc
index 5c7d01dca..2ac252ba1 100644
--- a/src/xenia/gpu/vulkan/vulkan_pipeline_cache.cc
+++ b/src/xenia/gpu/vulkan/vulkan_pipeline_cache.cc
@@ -1126,15 +1126,37 @@ void VulkanPipelineCache::WritePipelineRenderTargetDescription(
         /* 15 */ PipelineBlendFactor::kOneMinusConstantAlpha,
         /* 16 */ PipelineBlendFactor::kSrcAlphaSaturate,
     };
+    // Like kBlendFactorMap, but with the color factors changed to their alpha
+    // equivalents. Alpha is scalar, so hardware treats a _COLOR factor in the
+    // alpha slot as the matching _ALPHA factor.
+    static constexpr PipelineBlendFactor kBlendFactorAlphaMap[32] = {
+        /*  0 */ PipelineBlendFactor::kZero,
+        /*  1 */ PipelineBlendFactor::kOne,
+        /*  2 */ PipelineBlendFactor::kZero,  // ?
+        /*  3 */ PipelineBlendFactor::kZero,  // ?
+        /*  4 */ PipelineBlendFactor::kSrcAlpha,
+        /*  5 */ PipelineBlendFactor::kOneMinusSrcAlpha,
+        /*  6 */ PipelineBlendFactor::kSrcAlpha,
+        /*  7 */ PipelineBlendFactor::kOneMinusSrcAlpha,
+        /*  8 */ PipelineBlendFactor::kDstAlpha,
+        /*  9 */ PipelineBlendFactor::kOneMinusDstAlpha,
+        /* 10 */ PipelineBlendFactor::kDstAlpha,
+        /* 11 */ PipelineBlendFactor::kOneMinusDstAlpha,
+        /* 12 */ PipelineBlendFactor::kConstantAlpha,
+        /* 13 */ PipelineBlendFactor::kOneMinusConstantAlpha,
+        /* 14 */ PipelineBlendFactor::kConstantAlpha,
+        /* 15 */ PipelineBlendFactor::kOneMinusConstantAlpha,
+        /* 16 */ PipelineBlendFactor::kSrcAlphaSaturate,
+    };
     render_target_out.src_color_blend_factor =
         kBlendFactorMap[uint32_t(blend_control.color_srcblend)];
     render_target_out.dst_color_blend_factor =
         kBlendFactorMap[uint32_t(blend_control.color_destblend)];
     render_target_out.color_blend_op = blend_control.color_comb_fcn;
     render_target_out.src_alpha_blend_factor =
-        kBlendFactorMap[uint32_t(blend_control.alpha_srcblend)];
+        kBlendFactorAlphaMap[uint32_t(blend_control.alpha_srcblend)];
     render_target_out.dst_alpha_blend_factor =
-        kBlendFactorMap[uint32_t(blend_control.alpha_destblend)];
+        kBlendFactorAlphaMap[uint32_t(blend_control.alpha_destblend)];
     render_target_out.alpha_blend_op = blend_control.alpha_comb_fcn;
     if (!command_processor_.GetVulkanDevice()
              ->properties()