wehub-resource-sync
44 lines
1.9 KiB
HLSL
44 lines
1.9 KiB
HLSL
// DownsamplePS.hlsl
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// Samples a 2x2 area in the source texture and averages the result.
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// Assumes rendering to a render target half the width and height.
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// Input Texture (higher resolution)
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Texture2D SourceTexture : register(t0);
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// Sampler State (Linear is needed for good quality downsampling)
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SamplerState LinearSampler : register(s0);
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// Input structure from Vertex Shader
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struct PS_INPUT
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{
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float4 pos : SV_POSITION;
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float2 uv : TEXCOORD0;
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};
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// Pixel Shader Main Function
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float4 psMain(PS_INPUT input) : SV_Target
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{
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// Get dimensions of the source texture to calculate texel size
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float width, height;
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SourceTexture.GetDimensions(width, height);
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float2 texelSize = float2(1.0f / width, 1.0f / height);
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// Sample a 2x2 box filter around the source UV corresponding to this destination pixel center.
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// The input UV corresponds to the center of the target pixel.
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// We need to sample the four source texels that contribute to this target pixel.
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float2 uv00 = input.uv + texelSize * float2(-0.5f, -0.5f); // Top-left texel center in source
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float2 uv10 = input.uv + texelSize * float2( 0.5f, -0.5f); // Top-right
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float2 uv01 = input.uv + texelSize * float2(-0.5f, 0.5f); // Bottom-left
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float2 uv11 = input.uv + texelSize * float2( 0.5f, 0.5f); // Bottom-right
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float4 color = 0;
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color += SourceTexture.Sample(LinearSampler, uv00);
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color += SourceTexture.Sample(LinearSampler, uv10);
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color += SourceTexture.Sample(LinearSampler, uv01);
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color += SourceTexture.Sample(LinearSampler, uv11);
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return color * 0.25f; // Average the 4 samples
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// Alternative: Single bilinear sample at the center can also work well for 2x downsample.
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// return SourceTexture.Sample(LinearSampler, input.uv);
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}
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