Implementing alpha testing.

src/xenia/gpu/gl4/command_processor.cc

@@ -1812,14 +1812,6 @@ CommandProcessor::UpdateStatus CommandProcessor::UpdateState() {
 
   bool mismatch = false;
 
-  // Alpha testing -- ALPHAREF, ALPHAFUNC, ALPHATESTENABLE
-  // Deprecated in GL, implemented in shader.
-  // if(ALPHATESTENABLE && frag_out.a [<=/ALPHAFUNC] ALPHAREF) discard;
-  uint32_t color_control = regs[XE_GPU_REG_RB_COLORCONTROL].u32;
-  draw_batcher_.set_alpha_test((color_control & 0x4) != 0,  // ALPAHTESTENABLE
-                               color_control & 0x3,         // ALPHAFUNC
-                               regs[XE_GPU_REG_RB_ALPHA_REF].f32);
-
 #define CHECK_UPDATE_STATUS(status, mismatch, error_message) \
   {                                                          \
     if (status == UpdateStatus::kError) {                    \
@@ -2075,8 +2067,17 @@ CommandProcessor::UpdateStatus CommandProcessor::UpdateRasterizerState() {
 }
 
 CommandProcessor::UpdateStatus CommandProcessor::UpdateBlendState() {
+  auto& reg_file = *register_file_;
   auto& regs = update_blend_state_regs_;
 
+  // Alpha testing -- ALPHAREF, ALPHAFUNC, ALPHATESTENABLE
+  // Deprecated in GL, implemented in shader.
+  // if(ALPHATESTENABLE && frag_out.a [<=/ALPHAFUNC] ALPHAREF) discard;
+  uint32_t color_control = reg_file[XE_GPU_REG_RB_COLORCONTROL].u32;
+  draw_batcher_.set_alpha_test((color_control & 0x4) != 0,  // ALPAHTESTENABLE
+                               color_control & 0x3,         // ALPHAFUNC
+                               reg_file[XE_GPU_REG_RB_ALPHA_REF].f32);
+
   bool dirty = false;
   dirty |=
       SetShadowRegister(regs.rb_blendcontrol[0], XE_GPU_REG_RB_BLENDCONTROL_0);

src/xenia/gpu/gl4/draw_batcher.h

@@ -171,9 +171,9 @@ class DrawBatcher {
 
   // This must match GL4Shader's header.
   struct CommonHeader {
-    float4 window_scale;     // sx,sy, ?, ?
+    float4 window_scale;  // sx,sy, ?, ?
-    float4 vtx_fmt;          //
+    float4 vtx_fmt;       //
-    float4 alpha_test;       // alpha test enable, func, ref, ?
+    float4 alpha_test;    // alpha test enable, func, ref, ?
 
     // TODO(benvanik): pack tightly
     GLuint64 texture_samplers[32];

src/xenia/gpu/gl4/gl4_shader.cc

@@ -245,16 +245,32 @@ bool GL4Shader::PreparePixelShader(
   }
   has_prepared_ = true;
 
-  std::string source = GetHeader() +
+  std::string source =
-                       "layout(origin_upper_left) in vec4 gl_FragCoord;\n"
+      GetHeader() +
-                       "layout(location = 0) flat in uint draw_id;\n"
+      "layout(origin_upper_left) in vec4 gl_FragCoord;\n"
-                       "layout(location = 1) in VertexData vtx;\n"
+      "layout(location = 0) flat in uint draw_id;\n"
-                       "layout(location = 0) out vec4 oC[4];\n"
+      "layout(location = 1) in VertexData vtx;\n"
-                       "void processFragment(const in StateData state);\n"
+      "layout(location = 0) out vec4 oC[4];\n"
-                       "void main() {\n" +
+      "void processFragment(const in StateData state);\n"
-                       "  const StateData state = states[draw_id];\n"
+      "void applyAlphaTest(int alpha_func, float alpha_ref) {\n"
-                       "  processFragment(state);\n"
+      "  switch (alpha_func) {\n"
-                       "}\n";
+      "  case 0:                           discard;\n"
+      "  case 1: if (oC[0].a <  alpha_ref) discard; break;\n"
+      "  case 2: if (oC[0].a == alpha_ref) discard; break;\n"
+      "  case 3: if (oC[0].a <= alpha_ref) discard; break;\n"
+      "  case 4: if (oC[0].a >  alpha_ref) discard; break;\n"
+      "  case 5: if (oC[0].a != alpha_ref) discard; break;\n"
+      "  case 6: if (oC[0].a >= alpha_ref) discard; break;\n"
+      "  case 7:                           break;\n"
+      "  };\n"
+      "}\n"
+      "void main() {\n" +
+      "  const StateData state = states[draw_id];\n"
+      "  processFragment(state);\n"
+      "  if (state.alpha_test.x != 0.0) {\n"
+      "    applyAlphaTest(int(state.alpha_test.y), state.alpha_test.z);\n"
+      "  }\n"
+      "}\n";
 
   std::string translated_source =
       shader_translator_.TranslatePixelShader(this, program_cntl);

src/xenia/gpu/trace_viewer_main.cc

@@ -1166,6 +1166,10 @@ void DrawTextureInfo(TracePlayer& player, const Shader::SamplerDesc& desc) {
   ImGui::Columns(1);
 }
 
+static const char* kCompareFuncNames[] = {
+    "<false>", "<", "==", "<=", ">", "!=", ">=", "<true>",
+};
+
 void DrawStateUI(xe::ui::MainWindow* window, TracePlayer& player,
                  uint8_t* membase) {
   auto gs = static_cast<gl4::GL4GraphicsSystem*>(player.graphics_system());
@@ -1464,14 +1468,25 @@ void DrawStateUI(xe::ui::MainWindow* window, TracePlayer& player,
                       blend_color.y, blend_color.z, blend_color.w);
     ImGui::SameLine();
     ImGui::ColorButton(blend_color, true);
+
+    // Alpha testing -- ALPHAREF, ALPHAFUNC, ALPHATESTENABLE
+    // if(ALPHATESTENABLE && frag_out.a [<=/ALPHAFUNC] ALPHAREF) discard;
+    uint32_t color_control = regs[XE_GPU_REG_RB_COLORCONTROL].u32;
+    if ((color_control & 0x4) != 0) {
+      ImGui::BulletText("Alpha Test: discard if %s %.2f",
+                        kCompareFuncNames[color_control & 0x3],
+                        regs[XE_GPU_REG_RB_ALPHA_REF].f32);
+    } else {
+      ImGui::PushStyleColor(ImGuiCol_Text, kColorIgnored);
+      ImGui::BulletText("Alpha Test: disabled");
+      ImGui::PopStyleColor();
+    }
+
     ImGui::TreePop();
   }
   if (ImGui::TreeNode("Depth-Stencil State")) {
     auto rb_depthcontrol = regs[XE_GPU_REG_RB_DEPTHCONTROL].u32;
     auto rb_stencilrefmask = regs[XE_GPU_REG_RB_STENCILREFMASK].u32;
-    static const char* kCompareFuncNames[] = {
-        "<false>", "<", "==", "<=", ">", "!=", ">=", "<true>",
-    };
     if (rb_depthcontrol & 0x00000002) {
       ImGui::BulletText("Depth Test: enabled");
     } else {