[D3D12] HLSL alphatest

src/xenia/gpu/d3d12/d3d12_command_processor.cc

@@ -1032,6 +1032,8 @@ void D3D12CommandProcessor::UpdateSystemConstantValues(
   uint32_t sq_program_cntl = regs[XE_GPU_REG_SQ_PROGRAM_CNTL].u32;
   uint32_t sq_context_misc = regs[XE_GPU_REG_SQ_CONTEXT_MISC].u32;
   uint32_t rb_surface_info = regs[XE_GPU_REG_RB_SURFACE_INFO].u32;
+  uint32_t rb_colorcontrol = regs[XE_GPU_REG_RB_COLORCONTROL].u32;
+  uint32_t rb_alpha_ref = regs[XE_GPU_REG_RB_ALPHA_REF].u32;
 
   bool dirty = false;
 
@@ -1137,6 +1139,39 @@ void D3D12CommandProcessor::UpdateSystemConstantValues(
   system_constants_.ssaa_inv_scale[0] = ssaa_inv_scale_x;
   system_constants_.ssaa_inv_scale[1] = ssaa_inv_scale_y;
 
+  // Alpha test.
+  uint32_t alpha_test_enabled = (rb_colorcontrol & 0x8) ? 1 : 0;
+  dirty |= system_constants_.alpha_test_enabled != alpha_test_enabled;
+  system_constants_.alpha_test_enabled = alpha_test_enabled;
+  if (rb_colorcontrol & 0x8) {
+    uint32_t alpha_test_function = rb_colorcontrol & 0x7;
+    // 0: Never - fail in [-inf, +inf].
+    // 1: Less - fail in [ref, +inf].
+    // 2: Equal - pass in [ref, ref].
+    // 3: Less or equal - pass in [-inf, ref].
+    // 4: Greater - fail in [-inf, ref].
+    // 5: Not equal - fail in [ref, ref].
+    // 6: Greater or equal - pass in [ref, +inf].
+    // 7: Always - pass in [-inf, +inf].
+    uint32_t alpha_test_range_start =
+        (alpha_test_function == 1 || alpha_test_function == 2 ||
+         alpha_test_function == 5 || alpha_test_function == 6)
+            ? rb_alpha_ref
+            : 0xFF800000u;
+    uint32_t alpha_test_range_end =
+        (alpha_test_function == 2 || alpha_test_function == 3 ||
+         alpha_test_function == 4 || alpha_test_function == 5)
+            ? rb_alpha_ref
+            : 0x7F800000u;
+    uint32_t alpha_test_range_pass = (alpha_test_function & 0x2) ? 1 : 0;
+    dirty |= system_constants_.alpha_test_range[0] != alpha_test_range_start;
+    dirty |= system_constants_.alpha_test_range[1] != alpha_test_range_end;
+    dirty |= system_constants_.alpha_test_range_pass != alpha_test_range_pass;
+    system_constants_.alpha_test_range[0] = alpha_test_range_start;
+    system_constants_.alpha_test_range[1] = alpha_test_range_end;
+    system_constants_.alpha_test_range_pass = alpha_test_range_pass;
+  }
+
   // Color output index mapping.
   for (uint32_t i = 0; i < 4; ++i) {
     dirty |= system_constants_.color_output_map[i] !=

src/xenia/gpu/hlsl_shader_translator.cc

@@ -177,6 +177,9 @@ std::vector<uint8_t> HlslShaderTranslator::CompleteTranslation() {
       "  float xe_pixel_half_pixel_offset;\n"
       "  float2 xe_ssaa_inv_scale;\n"
       "  uint xe_pixel_pos_reg;\n"
+      "  bool xe_alpha_test_enabled;\n"
+      "  float2 xe_alpha_test_range;\n"
+      "  bool xe_alpha_test_range_pass;\n"
       "  uint4 xe_color_output_map;\n"
       "};\n"
       "\n"
@@ -382,15 +385,29 @@ std::vector<uint8_t> HlslShaderTranslator::CompleteTranslation() {
         "      xe_output.position.xyz * xe_ndc_scale +\n"
         "      xe_ndc_offset * xe_output.position.www;\n");
   } else if (is_pixel_shader()) {
+    source.Append(
+        // Perform alpha test - check if the alpha is within the specified
+        // bounds (inclusively), fail or pass depending on comparison mode and
+        // on the results of the bound test.
+        "  [branch] if (xe_alpha_test_enabled) {\n"
+        "    bool xe_alpha_test_failed =\n"
+        "        xe_color_output[0u].a >= xe_alpha_test_range.x &&\n"
+        "        xe_color_output[0u].a <= xe_alpha_test_range.y;\n"
+        "    [flatten] if (xe_alpha_test_range_pass) {\n"
+        "      xe_alpha_test_failed = !xe_alpha_test_failed;\n"
+        "    }\n"
+        "    if (xe_alpha_test_failed) {\n"
+        "      discard;\n"
+        "    }\n"
+        "  }\n"
         // Remap guest color outputs to host render targets because null render
         // target descriptors are broken.
-    source.Append(
         "  xe_output.colors[0] = xe_color_output[xe_color_output_map.r];\n"
         "  xe_output.colors[1] = xe_color_output[xe_color_output_map.g];\n"
         "  xe_output.colors[2] = xe_color_output[xe_color_output_map.b];\n"
         "  xe_output.colors[3] = xe_color_output[xe_color_output_map.a];\n");
   }
-  // TODO(Triang3l): Window offset, half pixel offset, alpha test, gamma.
+  // TODO(Triang3l): Half pixel offset, alpha test, gamma.
   source.Append(
       "  return xe_output;\n"
       "}\n");

src/xenia/gpu/hlsl_shader_translator.h

@@ -37,8 +37,13 @@ class HlslShaderTranslator : public ShaderTranslator {
     // vec4 3
     float ssaa_inv_scale[2];
     uint32_t pixel_pos_reg;
-    uint32_t padding_3;
+    uint32_t alpha_test_enabled;
     // vec4 4
+    // The range is floats as uints so it's easier to pass infinity.
+    uint32_t alpha_test_range[2];
+    uint32_t alpha_test_range_pass;
+    uint32_t padding_4;
+    // vec4 5
     uint32_t color_output_map[4];
   };