From 31168682b02bd0d03f81cbbab27786e8fcab3126 Mon Sep 17 00:00:00 2001
From: goldislead <69987043+goldislead@users.noreply.github.com>
Date: Sat, 8 Aug 2026 10:18:00 -0700
Subject: [PATCH] [Vulkan] Fix draw_resolution_scaled_texture_offsets
 cancelling itself out

The offset was being multiplied by the scale and divided by the host scaled size, which collapsed back to guest step, so the cvar changed nothing on Vulkan while D3D12 stepped host texels. Since the size is already in host texels, dividing the offset by it gives the proper step.

Unnormalized coordinates convert to host texels before the offset add so the offset isn't multiplied along with the coordinate. Folds in the fix for 5841095A.

Co-authored-by: Herman S. <429230+has207@users.noreply.github.com>
---
 .../gpu/spirv_shader_translator_fetch.cc      | 45 +++++--------------
 1 file changed, 12 insertions(+), 33 deletions(-)

diff --git a/src/xenia/gpu/spirv_shader_translator_fetch.cc b/src/xenia/gpu/spirv_shader_translator_fetch.cc
index fca5c9796..299a90854 100644
--- a/src/xenia/gpu/spirv_shader_translator_fetch.cc
+++ b/src/xenia/gpu/spirv_shader_translator_fetch.cc
@@ -1245,12 +1245,9 @@ void SpirvShaderTranslator::ProcessTextureFetchInstruction(
     } else {
       // kTextureFetch or kGetTextureComputedLod.
 
-      // Normalize the XY coordinates, and apply the offset.
-      // When a texture is from a resolution-scaled resolve, offsets are in
-      // guest texels but the size is in host texels. We need to scale offsets
-      // to compensate:
-      // - For normalized coords: coord + (offset * scale) / size_scaled
-      // - For unnormalized coords: (coord + offset) * scale / size_scaled
+      // Normalize the XY coordinates, and apply the offset. When the texture
+      // is resolution-scaled, size has already been scaled up to host texels
+      // above so dividing the offset by it yields a 1-host-texel step.
       for (uint32_t i = 0;
            i <= uint32_t(coordinate_dimension != xenos::FetchOpDimension::k1D);
            ++i) {
@@ -1260,15 +1257,10 @@ void SpirvShaderTranslator::ProcessTextureFetchInstruction(
                              : spv::NoResult;
         spv::Id size_component = size[i];
         if (instr.attributes.unnormalized_coordinates) {
-          if (component_offset != spv::NoResult) {
-            coordinate_ref = builder_->createNoContractionBinOp(
-                spv::OpFAdd, type_float_, coordinate_ref, component_offset);
-          }
-          // For resolution-scaled textures with unnormalized coords, we need
-          // to scale the coordinate (which now includes offset) before
-          // dividing by the scaled size. This ensures:
-          // (coord + offset) * scale / size_scaled = (coord + offset) /
-          // guest_size
+          // Convert the guest-texel coord to host texels for resolution-scaled
+          // textures, since size below is in host texels. Done before the
+          // offset add so the offset stays at 1 host texel rather than being
+          // multiplied with the coord.
           if (is_texture_resolved != spv::NoResult &&
               ((i == 0 && draw_resolution_scale_x_ > 1) ||
                (i == 1 && draw_resolution_scale_y_ > 1))) {
@@ -1281,32 +1273,19 @@ void SpirvShaderTranslator::ProcessTextureFetchInstruction(
                 spv::OpSelect, type_float_, is_texture_resolved, scaled_coord,
                 coordinate_ref);
           }
+          if (component_offset != spv::NoResult) {
+            coordinate_ref = builder_->createNoContractionBinOp(
+                spv::OpFAdd, type_float_, coordinate_ref, component_offset);
+          }
           assert_true(size_component != spv::NoResult);
           coordinate_ref = builder_->createNoContractionBinOp(
               spv::OpFDiv, type_float_, coordinate_ref, size_component);
         } else {
           if (component_offset != spv::NoResult) {
             assert_true(size_component != spv::NoResult);
-            // For resolution-scaled textures with normalized coords, scale the
-            // offset before normalizing. This ensures:
-            // coord + (offset * scale) / size_scaled = coord + offset /
-            // guest_size
-            spv::Id effective_offset = component_offset;
-            if (is_texture_resolved != spv::NoResult &&
-                ((i == 0 && draw_resolution_scale_x_ > 1) ||
-                 (i == 1 && draw_resolution_scale_y_ > 1))) {
-              float scale = (i == 0) ? float(draw_resolution_scale_x_)
-                                     : float(draw_resolution_scale_y_);
-              spv::Id scaled_offset = builder_->createNoContractionBinOp(
-                  spv::OpFMul, type_float_, component_offset,
-                  builder_->makeFloatConstant(scale));
-              effective_offset = builder_->createTriOp(
-                  spv::OpSelect, type_float_, is_texture_resolved,
-                  scaled_offset, component_offset);
-            }
             spv::Id component_offset_normalized =
                 builder_->createNoContractionBinOp(
-                    spv::OpFDiv, type_float_, effective_offset, size_component);
+                    spv::OpFDiv, type_float_, component_offset, size_component);
             coordinate_ref = builder_->createNoContractionBinOp(
                 spv::OpFAdd, type_float_, coordinate_ref,
                 component_offset_normalized);