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76 行
2.3 KiB
76 行
2.3 KiB
// Precomputes data for IntegrateLD(). See that function for a detailed description.
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#include "CoreRP/ShaderLibrary/Common.hlsl"
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#include "CoreRP/ShaderLibrary/ImageBasedLighting.hlsl"
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#ifdef SHADER_API_MOBILE
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#define MAX_IBL_SAMPLE_CNT 34
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#else
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#define MAX_IBL_SAMPLE_CNT 89
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#endif
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RWTexture2D<float4> output; // [MAX_SAMPLE_CNT x UNITY_SPECCUBE_LOD_STEPS]
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#pragma kernel ComputeGgxIblSampleData
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[numthreads(MAX_IBL_SAMPLE_CNT, UNITY_SPECCUBE_LOD_STEPS, 1)]
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void ComputeGgxIblSampleData(uint3 groupThreadId : SV_GroupThreadID)
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{
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uint sampleIndex = groupThreadId.x;
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uint mipLevel = groupThreadId.y + 1;
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float roughness = PerceptualRoughnessToRoughness(MipmapLevelToPerceptualRoughness(mipLevel));
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uint sampleCount = GetIBLRuntimeFilterSampleCount(mipLevel);
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if (sampleIndex >= sampleCount)
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{
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output[groupThreadId.xy] = float4(0, 0, 0, 0);
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return;
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}
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float3 V = float3(0, 0, 1);
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float NdotV = 1;
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float3 localL;
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float NdotL, NdotH, LdotH;
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const uint validSampleCount = sampleCount;
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while (true)
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{
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uint acceptedSampleCount = 0;
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uint shiftedSampleIndex = 0;
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for (uint i = 0; i < sampleCount; i++)
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{
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// We switch to the Golden sequence instead of the Fibonacci sequence
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// since the sample count is not guaranteed to be a Fibonacci number.
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// TODO: might be interesting to try Mitchell's Poisson disk sampling algorithm.
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// In our case, samples would not have disks associated with them, but rather solid angles.
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float2 u = Golden2dSeq(i, sampleCount);
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SampleGGXDir(u, V, k_identity3x3, roughness, localL, NdotL, NdotH, LdotH, true);
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if (NdotL > 0)
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{
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if (acceptedSampleCount == sampleIndex) shiftedSampleIndex = i;
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acceptedSampleCount++;
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}
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}
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if (acceptedSampleCount == validSampleCount)
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{
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sampleIndex = shiftedSampleIndex;
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break;
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}
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sampleCount++;
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}
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float2 u = Golden2dSeq(sampleIndex, sampleCount);
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SampleGGXDir(u, V, k_identity3x3, roughness, localL, NdotL, NdotH, LdotH, true);
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float pdf = 0.25 * D_GGX(NdotH, roughness);
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float omegaS = rcp(sampleCount) * rcp(pdf);
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output[groupThreadId.xy] = float4(localL, omegaS);
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}
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