Rasterizer: Implemented alpha testing.

src/video_core/pica.h

@@ -310,7 +310,7 @@ struct Regs {
     };
 
     struct {
-        enum DepthFunc : u32 {
+        enum CompareFunc : u32 {
             Never               = 0,
             Always              = 1,
             Equal               = 2,
@@ -357,11 +357,19 @@ struct Regs {
             BitField<0, 4, Op> op;
         } logic_op;
 
-        INSERT_PADDING_WORDS(0x4);
+        INSERT_PADDING_WORDS(0x1);
+
+        union {
+            BitField< 0, 1, u32> enable;
+            BitField< 4, 3, CompareFunc> func;
+            BitField< 8, 8, u32> ref;
+        } alpha_test;
+
+        INSERT_PADDING_WORDS(0x2);
 
         union {
             BitField< 0, 1, u32> depth_test_enable;
-            BitField< 4, 3, DepthFunc> depth_test_func;
+            BitField< 4, 3, CompareFunc> depth_test_func;
             BitField<12, 1, u32> depth_write_enable;
         };
 

src/video_core/rasterizer.cpp

@@ -431,6 +431,47 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
                 combiner_output = Math::MakeVec(color_output, alpha_output);
             }
 
+            if (registers.output_merger.alpha_test.enable) {
+                bool pass = false;
+
+                switch (registers.output_merger.alpha_test.func) {
+                case registers.output_merger.Never:
+                    pass = false;
+                    break;
+
+                case registers.output_merger.Always:
+                    pass = true;
+                    break;
+
+                case registers.output_merger.Equal:
+                    pass = combiner_output.a() == registers.output_merger.alpha_test.ref;
+                    break;
+
+                case registers.output_merger.NotEqual:
+                    pass = combiner_output.a() != registers.output_merger.alpha_test.ref;
+                    break;
+
+                case registers.output_merger.LessThan:
+                    pass = combiner_output.a() < registers.output_merger.alpha_test.ref;
+                    break;
+
+                case registers.output_merger.LessThanOrEqual:
+                    pass = combiner_output.a() <= registers.output_merger.alpha_test.ref;
+                    break;
+
+                case registers.output_merger.GreaterThan:
+                    pass = combiner_output.a() > registers.output_merger.alpha_test.ref;
+                    break;
+
+                case registers.output_merger.GreaterThanOrEqual:
+                    pass = combiner_output.a() >= registers.output_merger.alpha_test.ref;
+                    break;
+                }
+
+                if (!pass)
+                    continue;
+            }
+
             // TODO: Does depth indeed only get written even if depth testing is enabled?
             if (registers.output_merger.depth_test_enable) {
                 u16 z = (u16)(-(v0.screenpos[2].ToFloat32() * w0 +
@@ -472,10 +513,6 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
                 case registers.output_merger.GreaterThanOrEqual:
                     pass = z >= ref_z;
                     break;
-
-                default:
-                    LOG_ERROR(HW_GPU, "Unknown depth test function %x", registers.output_merger.depth_test_func.Value());
-                    break;
                 }
 
                 if (!pass)