From d0dd989238addf353d7435dfdb3d26049f1b08f8 Mon Sep 17 00:00:00 2001
From: bomabomabomaboma <69987043+goldislead@users.noreply.github.com>
Date: Fri, 31 Jul 2026 23:17:27 +0000
Subject: [PATCH] [GPU] Honor force_bc_w_to_max: force sampler border color
 alpha to 1.0

Co-authored-by: Herman S. <429230+has207@users.noreply.github.com>
---
 src/xenia/gpu/d3d12/d3d12_texture_cache.cc   |  4 ++++
 src/xenia/gpu/d3d12/d3d12_texture_cache.h    |  3 +++
 src/xenia/gpu/vulkan/vulkan_texture_cache.cc | 12 +++++++++---
 src/xenia/gpu/vulkan/vulkan_texture_cache.h  |  3 +++
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/xenia/gpu/d3d12/d3d12_texture_cache.cc b/src/xenia/gpu/d3d12/d3d12_texture_cache.cc
index a4de12e35..5226f5696 100644
--- a/src/xenia/gpu/d3d12/d3d12_texture_cache.cc
+++ b/src/xenia/gpu/d3d12/d3d12_texture_cache.cc
@@ -765,6 +765,7 @@ D3D12TextureCache::SamplerParameters D3D12TextureCache::GetSamplerParameters(
       xenos::ClampModeUsesBorder(parameters.clamp_y) ||
       xenos::ClampModeUsesBorder(parameters.clamp_z)) {
     parameters.border_color = fetch.border_color;
+    parameters.force_bc_w_to_max = fetch.force_bc_w_to_max;
   } else {
     parameters.border_color = xenos::BorderColor::k_ABGR_Black;
   }
@@ -891,6 +892,9 @@ void D3D12TextureCache::WriteSampler(SamplerParameters parameters,
       desc.BorderColor[3] = 0.0f;
       break;
   }
+  if (parameters.force_bc_w_to_max) {
+    desc.BorderColor[3] = 1.0f;
+  }
   desc.MinLOD = float(parameters.mip_min_level);
   if (parameters.mip_base_map) {
     // "It is undefined whether LOD clamping based on MinLOD and MaxLOD Sampler
diff --git a/src/xenia/gpu/d3d12/d3d12_texture_cache.h b/src/xenia/gpu/d3d12/d3d12_texture_cache.h
index c97e71586..599d42fb1 100644
--- a/src/xenia/gpu/d3d12/d3d12_texture_cache.h
+++ b/src/xenia/gpu/d3d12/d3d12_texture_cache.h
@@ -59,6 +59,9 @@ class D3D12TextureCache final : public TextureCache {
       xenos::AnisoFilter aniso_filter : 3;  // 17
       uint32_t mip_min_level : 4;           // 21
       uint32_t mip_base_map : 1;            // 22
+      // Force the border color alpha to 1.0 (only meaningful with a border
+      // clamp mode).
+      uint32_t force_bc_w_to_max : 1;  // 23
       // Maximum mip level is in the texture resource itself, but mip_base_map
       // can be used to limit fetching to mip_min_level.
     };
diff --git a/src/xenia/gpu/vulkan/vulkan_texture_cache.cc b/src/xenia/gpu/vulkan/vulkan_texture_cache.cc
index 54ba79664..1ad7ab2e0 100644
--- a/src/xenia/gpu/vulkan/vulkan_texture_cache.cc
+++ b/src/xenia/gpu/vulkan/vulkan_texture_cache.cc
@@ -668,6 +668,7 @@ VulkanTextureCache::SamplerParameters VulkanTextureCache::GetSamplerParameters(
       xenos::ClampModeUsesBorder(parameters.clamp_y) ||
       xenos::ClampModeUsesBorder(parameters.clamp_z)) {
     parameters.border_color = fetch.border_color;
+    parameters.force_bc_w_to_max = fetch.force_bc_w_to_max;
   } else {
     parameters.border_color = xenos::BorderColor::k_ABGR_Black;
   }
@@ -889,18 +890,23 @@ VkSampler VulkanTextureCache::UseSampler(SamplerParameters parameters,
           color[1] = 0.5f;
           color[2] = 0.5f;
         }
-        color[3] = 0.0f;
+        color[3] = parameters.force_bc_w_to_max ? 1.0f : 0.0f;
         custom_border_color.format = VK_FORMAT_UNDEFINED;
         custom_border_color.pNext = sampler_create_info.pNext;
         sampler_create_info.pNext = &custom_border_color;
         sampler_create_info.borderColor = VK_BORDER_COLOR_FLOAT_CUSTOM_EXT;
       } else {
         sampler_create_info.borderColor =
-            VK_BORDER_COLOR_FLOAT_TRANSPARENT_BLACK;
+            parameters.force_bc_w_to_max
+                ? VK_BORDER_COLOR_FLOAT_OPAQUE_BLACK
+                : VK_BORDER_COLOR_FLOAT_TRANSPARENT_BLACK;
       }
       break;
     default:
-      sampler_create_info.borderColor = VK_BORDER_COLOR_FLOAT_TRANSPARENT_BLACK;
+      sampler_create_info.borderColor =
+          parameters.force_bc_w_to_max
+              ? VK_BORDER_COLOR_FLOAT_OPAQUE_BLACK
+              : VK_BORDER_COLOR_FLOAT_TRANSPARENT_BLACK;
       break;
   }
   VkSampler vulkan_sampler;
diff --git a/src/xenia/gpu/vulkan/vulkan_texture_cache.h b/src/xenia/gpu/vulkan/vulkan_texture_cache.h
index fc9a0deb8..6cc0496cd 100644
--- a/src/xenia/gpu/vulkan/vulkan_texture_cache.h
+++ b/src/xenia/gpu/vulkan/vulkan_texture_cache.h
@@ -44,6 +44,9 @@ class VulkanTextureCache final : public TextureCache {
       xenos::AnisoFilter aniso_filter : 3;  // 17
       uint32_t mip_min_level : 4;           // 21
       uint32_t mip_base_map : 1;            // 22
+      // Force the border color alpha to 1.0 (only meaningful with a border
+      // clamp mode).
+      uint32_t force_bc_w_to_max : 1;  // 23
       // Maximum mip level is in the texture resource itself, but mip_base_map
       // can be used to limit fetching to mip_min_level.
     };