Wire up alphaToCoverage support

src/Device/Context.cpp

@@ -172,6 +172,7 @@ namespace sw
 
 		writeSRGB = false;
 		sampleMask = 0xFFFFFFFF;
+		alphaToCoverage = false;
 	}
 
 	bool Context::setDepthBufferEnable(bool depthBufferEnable)

src/Device/Context.hpp

@@ -201,6 +201,7 @@ namespace sw
 		unsigned int sampleMask;
 		unsigned int multiSampleMask;
 		int sampleCount;
+		bool alphaToCoverage;
 
 		PushConstantStorage pushConstants;
 	};

src/Device/PixelProcessor.cpp

@@ -282,11 +282,7 @@ namespace sw
 			state.shaderID = 0;
 		}
 
-		if(context->alphaTestActive())
-		{
-			state.transparencyAntialiasing = context->sampleCount > 1 ? transparencyAntialiasing : TRANSPARENCY_NONE;
-		}
-
+		state.alphaToCoverage = context->alphaToCoverage;
 		state.depthWriteEnable = context->depthWriteActive();
 
 		if(context->stencilActive())

src/Device/PixelProcessor.hpp

@@ -61,7 +61,7 @@ namespace sw
 			bool writeSRGB;
 			unsigned int multiSample;
 			unsigned int multiSampleMask;
-			TransparencyAntialiasing transparencyAntialiasing;
+			bool alphaToCoverage;
 			bool centroid;
 			bool frontFaceCCW;
 			VkFormat depthFormat;
@@ -80,11 +80,6 @@ namespace sw
 				return (colorWriteMask >> (index * 4)) & 0xF;
 			}
 
-			bool alphaTestActive() const
-			{
-				return transparencyAntialiasing != TRANSPARENCY_NONE;
-			}
-
 			unsigned int hash;
 		};
 

src/Device/Renderer.cpp

@@ -437,22 +437,19 @@ namespace sw
 
 		data->factor = factor;
 
-		if(pixelState.transparencyAntialiasing == TRANSPARENCY_ALPHA_TO_COVERAGE)
+		if(pixelState.alphaToCoverage)
 		{
-			float ref = context->alphaReference * (1.0f / 255.0f);
-			float margin = sw::min(ref, 1.0f - ref);
-
 			if(ms == 4)
 			{
-				data->a2c0 = replicate(ref - margin * 0.6f);
-				data->a2c1 = replicate(ref - margin * 0.2f);
-				data->a2c2 = replicate(ref + margin * 0.2f);
-				data->a2c3 = replicate(ref + margin * 0.6f);
+				data->a2c0 = replicate(0.2f);
+				data->a2c1 = replicate(0.4f);
+				data->a2c2 = replicate(0.6f);
+				data->a2c3 = replicate(0.8f);
 			}
 			else if(ms == 2)
 			{
-				data->a2c0 = replicate(ref - margin * 0.3f);
-				data->a2c1 = replicate(ref + margin * 0.3f);
+				data->a2c0 = replicate(0.25f);
+				data->a2c1 = replicate(0.75f);
 			}
 			else ASSERT(false);
 		}

src/Pipeline/PixelProgram.cpp

@@ -99,16 +99,12 @@ namespace sw
 
 	Bool PixelProgram::alphaTest(Int cMask[4])
 	{
-		if(!state.alphaTestActive())
+		if(!state.alphaToCoverage)
 		{
 			return true;
 		}
 
-		if(state.transparencyAntialiasing == TRANSPARENCY_ALPHA_TO_COVERAGE)
-		{
-			alphaToCoverage(cMask, c[0].w);
-		}
-		else ASSERT(false);
+		alphaToCoverage(cMask, c[0].w);
 
 		Int pass = cMask[0];
 
@@ -221,7 +217,7 @@ namespace sw
 	{
 		for(int index = 0; index < RENDERTARGETS; index++)
 		{
-			if(!state.colorWriteActive(index) && !(index == 0 && state.alphaTestActive()))
+			if(!state.colorWriteActive(index) && !(index == 0 && state.alphaToCoverage))
 			{
 				continue;
 			}

src/Pipeline/PixelRoutine.cpp

@@ -62,7 +62,8 @@ namespace sw
 			Long pipeTime = Ticks();
 		#endif
 
-		const bool earlyDepthTest = !spirvShader->getModes().DepthReplacing && !state.alphaTestActive();
+		// TODO: consider shader which modifies sample mask in general
+		const bool earlyDepthTest = !spirvShader->getModes().DepthReplacing && !state.alphaToCoverage;
 
 		Int zMask[4];   // Depth mask
 		Int sMask[4];   // Stencil mask
@@ -194,7 +195,7 @@ namespace sw
 
 				alphaPass = alphaTest(cMask);
 
-				if((spirvShader && spirvShader->getModes().ContainsKill) || state.alphaTestActive())
+				if((spirvShader && spirvShader->getModes().ContainsKill) || state.alphaToCoverage)
 				{
 					for(unsigned int q = 0; q < state.multiSample; q++)
 					{
@@ -2476,6 +2477,6 @@ namespace sw
 
 	bool PixelRoutine::colorUsed()
 	{
-		return state.colorWriteMask || state.alphaTestActive() || (spirvShader && spirvShader->getModes().ContainsKill);
+		return state.colorWriteMask || state.alphaToCoverage || (spirvShader && spirvShader->getModes().ContainsKill);
 	}
 }

src/Vulkan/VkPipeline.cpp

@@ -355,9 +355,10 @@ GraphicsPipeline::GraphicsPipeline(const VkGraphicsPipelineCreateInfo* pCreateIn
 		if (multisampleState->pSampleMask)
 			context.sampleMask = multisampleState->pSampleMask[0];
 
+		context.alphaToCoverage = (multisampleState->alphaToCoverageEnable == VK_TRUE);
+
 		if((multisampleState->flags != 0) ||
 			(multisampleState->sampleShadingEnable != 0) ||
-				(multisampleState->alphaToCoverageEnable != 0) ||
 			(multisampleState->alphaToOneEnable != 0))
 		{
 			UNIMPLEMENTED("multisampleState");