99 lines
2.5 KiB
HLSL
99 lines
2.5 KiB
HLSL
// Copyright Epic Games, Inc. All Rights Reserved.
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/*=============================================================================
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PostProcessDownsample.usf: PostProcessing down sample.
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=============================================================================*/
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#define SCENE_TEXTURES_DISABLED 1
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#include "Common.ush"
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#include "ScreenPass.ush"
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#include "PostProcessCommon.ush"
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#define DOWNSAMPLE_QUALITY_LOW 0
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#define DOWNSAMPLE_QUALITY_HIGH 1
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#ifndef DOWNSAMPLE_QUALITY
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#error DOWNSAMPLE_QUALITY is not defined.
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#endif
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Texture2D InputTexture;
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SamplerState InputSampler;
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SCREEN_PASS_TEXTURE_VIEWPORT(Input)
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SCREEN_PASS_TEXTURE_VIEWPORT(Output)
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float4 SampleInput(float2 UV)
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{
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UV = clamp(UV, Input_UVViewportBilinearMin, Input_UVViewportBilinearMax);
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return Texture2DSampleLevel(InputTexture, InputSampler, UV, 0);
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}
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float4 DownsampleCommon(float2 UV)
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{
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float4 OutColor;
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#if DOWNSAMPLE_QUALITY == DOWNSAMPLE_QUALITY_LOW
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// Output: low quality, 1 filtered sample
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OutColor = SampleInput(UV);
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#elif DOWNSAMPLE_QUALITY == DOWNSAMPLE_QUALITY_HIGH
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// Output: float4(RGBA), 4 filtered samples
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float2 UVs[4];
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// Blur during downsample (4x4 kernel) to get better quality especially for HDR content.
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UVs[0] = UV + Input_ExtentInverse * float2(-1, -1);
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UVs[1] = UV + Input_ExtentInverse * float2( 1, -1);
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UVs[2] = UV + Input_ExtentInverse * float2(-1, 1);
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UVs[3] = UV + Input_ExtentInverse * float2( 1, 1);
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float4 Sample[4];
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UNROLL
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for(uint i = 0; i < 4; ++i)
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{
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Sample[i] = SampleInput(UVs[i]);
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}
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OutColor = (Sample[0] + Sample[1] + Sample[2] + Sample[3]) * 0.25f;
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// Fixed rarely occurring yellow color tint of the whole viewport (certain viewport size, need to investigate more)
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OutColor.rgb = max(float3(0,0,0), OutColor.rgb);
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#else
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#error Invalid quality level specified.
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#endif
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return OutColor;
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}
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// pixel shader entry point
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#if PIXELSHADER
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void MainPS(float4 SvPosition : SV_POSITION, out float4 OutColor : SV_Target0)
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{
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const float2 UV = SvPosition.xy * Output_ExtentInverse;
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OutColor = DownsampleCommon(UV);
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}
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#elif COMPUTESHADER
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FScreenTransform DispatchThreadIdToInputUV;
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RWTexture2D<float4> OutComputeTexture;
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[numthreads(THREADGROUP_SIZEX, THREADGROUP_SIZEY, 1)]
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void MainCS(uint2 DispatchThreadId : SV_DispatchThreadID)
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{
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float2 InputUV = ApplyScreenTransform(float2(DispatchThreadId), DispatchThreadIdToInputUV);
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uint2 OutputPixelPos = DispatchThreadId + Output_ViewportMin;
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if (all(OutputPixelPos < Output_ViewportMax))
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{
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OutComputeTexture[OutputPixelPos] = DownsampleCommon(InputUV);
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}
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}
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#endif
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