UnrealEngineUWP/Engine/Shaders/PostProcessGBufferHints.usf

// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	PostProcessGBufferHints.usf: PostProcessing shader to show where material have performance issues or are unrealistic
=============================================================================*/

#include "Common.usf"
#include "PostProcessCommon.usf"
#include "PostProcessHistogramCommon.usf"
#include "DeferredShadingCommon.usf"

// 0: good, 1: heavy performance cost, 2:warning (very uncommon material), 3:error (impossibele material attributes)
uint ComputeAdvice(FGBufferData BufferData, float3 OriginalSceneColor)
{
	float SubsurfaceLum = 0;
	const float OneThird = 1.0f / 3.0f;

	FLATTEN if(BufferData.ShadingModelID != SHADINGMODELID_UNLIT)
	{
		FLATTEN if(BufferData.ShadingModelID == SHADINGMODELID_SUBSURFACE)
		{
			SubsurfaceLum = dot(OneThird.xxx, ExtractSubsurfaceColor(BufferData));
		}

		float DiffuseLum = dot(OneThird.xxx, BufferData.DiffuseColor);
		float SpecularLum = dot(OneThird.xxx, BufferData.SpecularColor);

		float TotalLum = DiffuseLum + SpecularLum + SubsurfaceLum;

		float OriginalSceneColorLum = dot(OneThird.xxx, OriginalSceneColor);

		/*FLATTEN if()
		{
			// heavy shading cost
			return 1;
		}*/

		FLATTEN if(TotalLum < 0.01f && OriginalSceneColorLum < 0.001f)
		{
			// The material is very dark. 
			// Such a material would be very unlikely (Maybe it can only be created in a lab).
			return 2;
		}

		FLATTEN if(TotalLum > 1.2f)
		{
			// The diffuse and specular cause the material to emit more light than it receives.
			return 3;
		}
	}

	return 0;
}

uint ComputeAdvice(float2 UV)
{
	// Ideally without GI as we want the emissive, we should do that later.
	float3 OriginalSceneColor = Texture2DSample(PostprocessInput1, PostprocessInput1Sampler, UV).rgb;
	FGBufferData BufferData = GetGBufferData(UV);

	return ComputeAdvice(BufferData, OriginalSceneColor);
}

// to highlight areas that have unrealistic materials
void HighlightAdvice(inout float3 OutColor, float2 UV, uint2 PixelPos)
{
	uint AdviceInner = ComputeAdvice(UV);
	uint AdviceOuter = 0;

	bool SpecialDotInArea = ((PixelPos.x + PixelPos.y) % 6) == 0 && ((PixelPos.x - PixelPos.y) % 6) == 0;
	
	AdviceOuter = max(AdviceOuter, ComputeAdvice(UV + float2( 1,  0) * PostprocessInput0Size.zw));
	AdviceOuter = max(AdviceOuter, ComputeAdvice(UV + float2( 0,  1) * PostprocessInput0Size.zw));
	AdviceOuter = max(AdviceOuter, ComputeAdvice(UV + float2(-1,  0) * PostprocessInput0Size.zw));
	AdviceOuter = max(AdviceOuter, ComputeAdvice(UV + float2( 0, -1) * PostprocessInput0Size.zw));

	uint Advice = (AdviceInner == AdviceOuter && !SpecialDotInArea) ? 0 : AdviceOuter;

	FLATTEN if(Advice)
	{
		 FLATTEN if(Advice == 1)
		 {
			 // heavy shading cost
			 OutColor = float3(0, 0, 0.8f);
		 }
		 else
		 FLATTEN if(Advice == 2)
		 {
			 // warning
			 OutColor = float3(0.8f, 0.8f, 0);
		 }
		 else // if(Advice == 3)
		 {
			 // error
			 OutColor = float3(1, 0, 0);
		 }
	}
}

void MainPS(noperspective float4 UVAndScreenPos : TEXCOORD0, float4 SvPosition : SV_POSITION, out float4 OutColor : SV_Target0)
{
	float2 UV = UVAndScreenPos.xy;
	int2 PixelPos = (uint2)SvPosition.xy;
	
	// background is the scene color
	OutColor = Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UV);

	HighlightAdvice(OutColor.rgb, UV, PixelPos);
}