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446 行
18 KiB
446 行
18 KiB
// =============== Convolves transmitted radiance with the Disney diffusion profile ================
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//--------------------------------------------------------------------------------------------------
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// Definitions
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//--------------------------------------------------------------------------------------------------
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// #pragma enable_d3d11_debug_symbols
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// Tweak parameters.
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#define SSS_BILATERAL_FILTER 1
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#define SSS_USE_LDS_CACHE 1
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#define SSS_TAA_INTEGRATION 1 // Smoother results at the cost of a tiny amount of flickering in under-sampled areas
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#define SSS_ENABLE_NEAR_FIELD 0 // Greatly increases the number of samples. Comes at a high cost.
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#define SSS_SAMPLE_TEST_HTILE 0 // Potential optimization. YMMV.
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#define SSS_USE_TANGENT_PLANE 0 // Improves the accuracy of the approximation(0 -> 1st order). High cost. Does not work with back-facing normals.
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#define SSS_CLAMP_ARTIFACT 0 // Reduces bleeding. Use with SSS_USE_TANGENT_PLANE.
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#define SSS_DEBUG_LOD 0
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#define SSS_DEBUG_NORMAL_VS 0
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// Do not modify these.
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#include "../../ShaderPass/ShaderPass.cs.hlsl"
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#define SHADERPASS SHADERPASS_SUBSURFACE_SCATTERING
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#define GROUP_SIZE_1D 16
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#define GROUP_SIZE_2D (GROUP_SIZE_1D * GROUP_SIZE_1D)
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#define TEXTURE_CACHE_BORDER 2
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#define TEXTURE_CACHE_SIZE_1D (GROUP_SIZE_1D + 2 * TEXTURE_CACHE_BORDER)
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// Check for support of typed UAV loads from FORMAT_R16G16B16A16_FLOAT.
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// TODO: query the format support more precisely.
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#if !(defined(SHADER_API_PSSL) || defined(SHADER_API_XBOXONE))
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#define USE_INTERMEDIATE_BUFFER
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#endif
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//--------------------------------------------------------------------------------------------------
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// Included headers
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//--------------------------------------------------------------------------------------------------
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#include "ShaderLibrary/Common.hlsl"
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#include "ShaderLibrary/Packing.hlsl"
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#include "ShaderLibrary/Sampling/Sampling.hlsl"
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#include "ShaderLibrary/SpaceFillingCurves.hlsl"
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#include "../../ShaderVariables.hlsl"
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#include "../../Lighting/LightDefinition.cs.hlsl"
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#include "SubsurfaceScattering.hlsl"
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//--------------------------------------------------------------------------------------------------
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// Inputs & outputs
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//--------------------------------------------------------------------------------------------------
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float4 _FilterKernels[SSS_N_PROFILES][SSS_N_SAMPLES_NEAR_FIELD]; // XY = near field, ZW = far field; 0 = radius, 1 = reciprocal of the PDF
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TEXTURE2D(_DepthTexture); // Z-buffer
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TEXTURE2D(_SSSHTile); // DXGI_FORMAT_R8_UINT is not supported by Unity
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TEXTURE2D(_IrradianceSource); // Includes transmitted light
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#ifdef USE_INTERMEDIATE_BUFFER
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RW_TEXTURE2D(float4, _CameraFilteringTexture); // Target texture
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#else
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RW_TEXTURE2D(float4, _CameraColorTexture); // Target texture
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#endif
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//--------------------------------------------------------------------------------------------------
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// Implementation
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//--------------------------------------------------------------------------------------------------
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// 6656 bytes used. It appears that the reserved LDS space must be a multiple of 512 bytes.
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#if SSS_USE_LDS_CACHE
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groupshared float4 textureCache[TEXTURE_CACHE_SIZE_1D * TEXTURE_CACHE_SIZE_1D]; // {irradiance, linearDepth}
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#endif
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groupshared bool processGroup;
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#if SSS_USE_LDS_CACHE
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float4 LoadSampleFromCacheMemory(int2 cacheCoord)
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{
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return textureCache[Mad24(TEXTURE_CACHE_SIZE_1D, cacheCoord.y, cacheCoord.x)];
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}
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#endif
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float4 LoadSampleFromVideoMemory(int2 pixelCoord)
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{
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float3 irradiance = LOAD_TEXTURE2D(_IrradianceSource, pixelCoord).rgb;
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float depth = LOAD_TEXTURE2D(_DepthTexture, pixelCoord).r;
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return float4(irradiance, LinearEyeDepth(depth, _ZBufferParams));
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}
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// Returns {irradiance, linearDepth}.
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float4 LoadSample(int2 pixelCoord, int2 cacheOffset)
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{
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#if SSS_USE_LDS_CACHE
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int2 cacheCoord = pixelCoord - cacheOffset;
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bool isInCache = max((uint)cacheCoord.x, (uint)cacheCoord.y) < TEXTURE_CACHE_SIZE_1D;
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[branch] if (isInCache)
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{
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return LoadSampleFromCacheMemory(cacheCoord);
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}
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else
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#endif
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{
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// Always load both irradiance and depth.
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// Avoid dependent texture reads at the cost of extra bandwidth.
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return LoadSampleFromVideoMemory(pixelCoord);
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}
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}
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// Computes the value of the integrand in polar coordinates: f(r, s) = r * R(r, s).
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// f(r, s) = (Exp[-r * s] + Exp[-r * s / 3]) * (s / (8 * Pi))
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// We can drop the constant (s / (8 * Pi)) due to the subsequent weight renormalization.
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float3 DisneyProfilePolar(float r, float3 S)
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{
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#if 0
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float3 expOneThird = exp(((-1.0 / 3.0) * r) * S);
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#else
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// Help the compiler.
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float k = (-1.0 / 3.0) * LOG2_E;
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float3 p = (k * r) * S;
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float3 expOneThird = exp2(p);
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#endif
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return expOneThird + expOneThird * expOneThird * expOneThird;
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}
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// Computes f(r, s)/p(r, s), s.t. r = sqrt(xy^2 + z^2).
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// Rescaling of the PDF is handled by 'totalWeight'.
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float3 ComputeBilateralWeight(float xy2, float z, float mmPerUnit, float3 S, float rcpPdf)
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{
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#if (SSS_BILATERAL_FILTER == 0)
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z = 0;
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#endif
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#if SSS_USE_TANGENT_PLANE
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// Both 'xy2' and 'z' require conversion to millimeters.
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float r = sqrt(xy2 + z * z) * mmPerUnit;
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#else
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// Only 'z' requires conversion to millimeters.
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float r = sqrt(xy2 + (z * mmPerUnit) * (z * mmPerUnit));
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#endif
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#if SSS_CLAMP_ARTIFACT
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return saturate(DisneyProfilePolar(r, S) * rcpPdf);
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#else
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return DisneyProfilePolar(r, S) * rcpPdf;
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#endif
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}
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void EvaluateSample(uint i, uint n, uint profileID, uint iR, uint iP, float2 centerCoord, int2 cacheOffset,
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float3 shapeParam, float3 centerPosVS, float mmPerUnit, float2 pixelsPerMm,
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float3 tangentX, float3 tangentY, float4x4 projMatrix,
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inout float3 totalIrradiance, inout float3 totalWeight)
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{
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float r = _FilterKernels[profileID][i][iR];
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// The relative sample position is known at the compile time.
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float phi = SampleDiskFibonacci(i, n).y;
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#if (SSS_TAA_INTEGRATION != 0)
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// Note that we repeat the pattern twice during the TAA cycle to reduce flickering.
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phi += VanDerCorputBase2(_TaaFrameIndex % 4) * TWO_PI;
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#endif
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float2 vec = r * float2(cos(phi), sin(phi));
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// Compute the screen-space position and the squared distance (in mm) in the image plane.
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int2 position; float xy2;
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#if SSS_USE_TANGENT_PLANE
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float3 relPosVS = vec.x * tangentX + vec.y * tangentY;
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float3 positionVS = centerPosVS + relPosVS;
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float2 positionNDC = ComputeNormalizedDeviceCoordinates(positionCS, projMatrix);
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position = (int2)(positionNDC * _ScreenSize.xy);
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xy2 = dot(relPosVS.xy, relPosVS.xy);
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#else
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position = (int2)(centerCoord + vec * pixelsPerMm);
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xy2 = r * r;
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#endif
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float4 textureSample = LoadSample(position, cacheOffset);
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float3 irradiance = textureSample.rgb;
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// Check the results of the stencil test.
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if (TestLightingForSSS(irradiance))
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{
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// Apply bilateral weighting.
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float viewZ = textureSample.a;
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float relZ = viewZ - centerPosVS.z;
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float rcpPdf = _FilterKernels[profileID][i][iP];
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float3 weight = ComputeBilateralWeight(xy2, relZ, mmPerUnit, shapeParam, rcpPdf);
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// Note: if the texture sample if off-screen, (z = 0) -> (viewZ = far) -> (weight ≈ 0).
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totalIrradiance += weight * irradiance;
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totalWeight += weight;
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}
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else
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{
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// The irradiance is 0. This could happen for 2 reasons.
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// Most likely, the surface fragment does not have an SSS material.
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// Alternatively, our sample comes from a region without any geometry.
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// Our blur is energy-preserving, so 'centerWeight' should be set to 0.
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// We do not terminate the loop since we want to gather the contribution
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// of the remaining samples (e.g. in case of hair covering skin).
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}
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}
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void StoreResult(uint2 pixelCoord, float3 irradiance)
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{
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#ifdef USE_INTERMEDIATE_BUFFER
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_CameraFilteringTexture[pixelCoord] = float4(irradiance, 1);
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#else
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_CameraColorTexture[pixelCoord] += float4(irradiance, 0);
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#endif
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}
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#pragma kernel SubsurfaceScattering
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[numthreads(GROUP_SIZE_2D, 1, 1)]
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void SubsurfaceScattering(uint3 reorderedGroupId : SV_GroupID,
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uint groupThreadId : SV_GroupThreadID)
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{
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// Note: any factor of 64 is a suitable wave size for our algorithm.
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uint waveIndex = WaveReadFirstLane(groupThreadId / 64);
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uint laneIndex = groupThreadId % 64;
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uint quadIndex = laneIndex / 4;
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// We dispatch 4x swizzled 16x16 groups per a 32x32 macrotile.
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// Therefore, we need to reorder. TODO: macrotile order.
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uint2 groupQuad = DeinterleaveQuad(reorderedGroupId.x);
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uint2 groupId = uint2(reorderedGroupId.y * 2 + groupQuad.x, reorderedGroupId.z * 2 + groupQuad.y);
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// Arrange threads in the Morton order to optimally match the memory layout of GCN tiles.
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uint2 groupCoord = DecodeMorton2D(groupThreadId);
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uint2 groupOffset = groupId * GROUP_SIZE_1D;
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uint2 pixelCoord = groupOffset + groupCoord;
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int2 cacheOffset = (int2)groupOffset - TEXTURE_CACHE_BORDER;
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[branch] if (groupThreadId == 0)
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{
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float stencilRef = STENCILLIGHTINGUSAGE_SPLIT_LIGHTING;
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// Check whether the thread group needs to perform any work.
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float s00 = LOAD_TEXTURE2D(_SSSHTile, 2 * groupId + uint2(0, 0)).r;
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float s10 = LOAD_TEXTURE2D(_SSSHTile, 2 * groupId + uint2(1, 0)).r;
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float s01 = LOAD_TEXTURE2D(_SSSHTile, 2 * groupId + uint2(0, 1)).r;
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float s11 = LOAD_TEXTURE2D(_SSSHTile, 2 * groupId + uint2(1, 1)).r;
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// Perform the stencil test (reject at the tile rate).
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processGroup = (stencilRef == s00 || stencilRef == s10 || stencilRef == s01 || stencilRef == s11);
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}
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// Wait for the LDS.
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GroupMemoryBarrierWithGroupSync();
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[branch] if (!processGroup) { return; }
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float3 centerIrradiance = LOAD_TEXTURE2D(_IrradianceSource, pixelCoord).rgb;
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float centerDepth = 0;
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float centerViewZ = 0;
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bool passedStencilTest = TestLightingForSSS(centerIrradiance);
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// Save some bandwidth by only loading depth values for SSS pixels.
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[branch] if (passedStencilTest)
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{
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centerDepth = LOAD_TEXTURE2D(_DepthTexture, pixelCoord).r;
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centerViewZ = LinearEyeDepth(centerDepth, _ZBufferParams);
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}
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#if SSS_USE_LDS_CACHE
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uint2 cacheCoord = groupCoord + TEXTURE_CACHE_BORDER;
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// Populate the central region of the LDS cache.
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textureCache[Mad24(TEXTURE_CACHE_SIZE_1D, cacheCoord.y, cacheCoord.x)] = float4(centerIrradiance, centerViewZ);
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uint numBorderQuadsPerWave = TEXTURE_CACHE_SIZE_1D / 2 - 1;
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uint halfCacheWidthInQuads = TEXTURE_CACHE_SIZE_1D / 4;
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[branch] if (quadIndex < numBorderQuadsPerWave)
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{
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// Fetch another texel into the LDS.
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uint2 startQuad = halfCacheWidthInQuads * DeinterleaveQuad(waveIndex);
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uint2 quadCoord;
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// The traversal order is such that the quad's X coordinate is monotonically increasing.
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// The corner is always the near the block of the corresponding wavefront.
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// Note: the compiler can heavily optimize the code below, as the switch is scalar,
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// and there are very few unique values due to the symmetry.
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switch (waveIndex)
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{
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case 0: // Bottom left
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quadCoord.x = max(0, (int)(quadIndex - (halfCacheWidthInQuads - 1)));
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quadCoord.y = max(0, (int)((halfCacheWidthInQuads - 1) - quadIndex));
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break;
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case 1: // Bottom right
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quadCoord.x = min(quadIndex, halfCacheWidthInQuads - 1);
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quadCoord.y = max(0, (int)(quadIndex - (halfCacheWidthInQuads - 1)));
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break;
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case 2: // Top left
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quadCoord.x = max(0, (int)(quadIndex - (halfCacheWidthInQuads - 1)));
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quadCoord.y = min(quadIndex, halfCacheWidthInQuads - 1);
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break;
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default: // Top right
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quadCoord.x = min(quadIndex, halfCacheWidthInQuads - 1);
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quadCoord.y = min(halfCacheWidthInQuads - 1, 2 * (halfCacheWidthInQuads - 1) - quadIndex);
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break;
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}
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uint2 cacheCoord2 = 2 * (startQuad + quadCoord) + DeinterleaveQuad(laneIndex);
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int2 pixelCoord2 = (int2)(groupOffset + cacheCoord2) - TEXTURE_CACHE_BORDER;
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float3 irradiance2 = LOAD_TEXTURE2D(_IrradianceSource, pixelCoord2).rgb;
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float viewZ2 = 0;
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// Save some bandwidth by only loading depth values for SSS pixels.
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[branch] if (TestLightingForSSS(irradiance2))
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{
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viewZ2 = LinearEyeDepth(LOAD_TEXTURE2D(_DepthTexture, pixelCoord2).r, _ZBufferParams);
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}
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// Populate the border region of the LDS cache.
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textureCache[Mad24(TEXTURE_CACHE_SIZE_1D, cacheCoord2.y, cacheCoord2.x)] = float4(irradiance2, viewZ2);
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}
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// Wait for the LDS.
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GroupMemoryBarrierWithGroupSync();
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#endif
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[branch] if (!passedStencilTest) { return; }
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PositionInputs posInput = GetPositionInput(pixelCoord, _ScreenSize.zw);
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// The result of the stencil test allows us to statically determine the material type (SSS).
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SSSData sssData;
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DECODE_FROM_SSSBUFFER(posInput.positionSS, sssData);
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int profileID = sssData.subsurfaceProfile;
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float distScale = sssData.subsurfaceRadius;
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float3 shapeParam = _ShapeParams[profileID].rgb;
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float maxDistance = _ShapeParams[profileID].a;
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// Reconstruct the view-space position corresponding to the central sample.
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float2 centerPosNDC = posInput.positionNDC;
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float2 cornerPosNDC = centerPosNDC + 0.5 * _ScreenSize.zw;
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float3 centerPosVS = ComputeViewSpacePosition(centerPosNDC, centerDepth, UNITY_MATRIX_I_P);
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float3 cornerPosVS = ComputeViewSpacePosition(cornerPosNDC, centerDepth, UNITY_MATRIX_I_P);
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// Rescaling the filter is equivalent to inversely scaling the world.
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float mmPerUnit = MILLIMETERS_PER_METER * (_WorldScales[profileID].x / distScale);
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float unitsPerMm = rcp(mmPerUnit);
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// Compute the view-space dimensions of the pixel as a quad projected onto geometry.
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float2 unitsPerPixel = 2 * abs(cornerPosVS.xy - centerPosVS.xy);
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float2 pixelsPerMm = rcp(unitsPerPixel) * unitsPerMm;
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// We perform point sampling. Therefore, we can avoid the cost
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// of filtering if we stay within the bounds of the current pixel.
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// We use the value of 1 instead of 0.5 as an optimization.
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// N.b.: our LoD selection algorithm is the same regardless of
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// whether we integrate over the tangent plane or not, since we
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// don't want the orientation of the tangent plane to create
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// divergence of execution across the warp.
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float maxDistInPixels = maxDistance * max(pixelsPerMm.x, pixelsPerMm.y);
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float3 albedo = ApplyDiffuseTexturingMode(sssData.diffuseColor, profileID);
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[branch] if (distScale == 0 || maxDistInPixels < 1)
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{
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#if SSS_DEBUG_LOD
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StoreResult(pixelCoord, float3(0, 0, 1));
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#else
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StoreResult(pixelCoord, albedo * centerIrradiance);
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#endif
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return;
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}
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float4x4 viewMatrix, projMatrix;
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GetLeftHandedViewSpaceMatrices(viewMatrix, projMatrix);
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// TODO: Since we have moved to forward SSS, we don't support anymore a bsdfData.normalWS.
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// Once we include normal+roughness rendering during the prepass, we will have a buffer to bind here and we will be able to reuse this part of the algorithm on demand.
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#if SSS_USE_TANGENT_PLANE
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#error ThisWillNotCompile_SeeComment
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// Compute the tangent frame in view space.
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float3 normalVS = mul((float3x3)viewMatrix, bsdfData.normalWS);
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float3 tangentX = GetLocalFrame(normalVS)[0] * unitsPerMm;
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float3 tangentY = GetLocalFrame(normalVS)[1] * unitsPerMm;
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#else
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float3 normalVS = float3(0, 0, 0);
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float3 tangentX = float3(0, 0, 0);
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float3 tangentY = float3(0, 0, 0);
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#endif
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#if SSS_DEBUG_NORMAL_VS
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// We expect the normal to be front-facing.
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float3 viewDirVS = normalize(centerPosVS);
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if (dot(normalVS, viewDirVS) >= 0)
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{
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StoreResult(pixelCoord, float3(1, 1, 1));
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return;
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}
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#endif
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// Use more samples for SS regions larger than 5x5 pixels (rotated by 45 degrees).
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bool useNearFieldKernel = SSS_ENABLE_NEAR_FIELD && maxDistInPixels > SSS_LOD_THRESHOLD;
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#if SSS_DEBUG_LOD
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StoreResult(pixelCoord, useNearFieldKernel ? float3(1, 0, 0) : float3(0.5, 0.5, 0));
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return;
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#endif
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// Compute the indices used to access the individual components of the float4 of the kernel.
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uint iR = useNearFieldKernel ? 0 : 2; // radius
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uint iP = useNearFieldKernel ? 1 : 3; // rcp(pdf)
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float centerRadius = _FilterKernels[profileID][0][iR];
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float centerRcpPdf = _FilterKernels[profileID][0][iP];
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float3 centerWeight = DisneyProfilePolar(centerRadius, shapeParam) * centerRcpPdf;
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// Accumulate filtered irradiance and bilateral weights (for renormalization).
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float3 totalIrradiance = centerWeight * centerIrradiance;
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float3 totalWeight = centerWeight;
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int i, n; // Declare once to avoid the warning from the Unity shader compiler.
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[unroll]
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for (i = 1, n = SSS_N_SAMPLES_FAR_FIELD; i < n; i++)
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{
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// Integrate over the image or tangent plane in the view space.
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EvaluateSample(i, n, profileID, iR, iP, pixelCoord + 0.5, cacheOffset,
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shapeParam, centerPosVS, mmPerUnit, pixelsPerMm,
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tangentX, tangentY, projMatrix,
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totalIrradiance, totalWeight);
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}
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[branch] if (!useNearFieldKernel)
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{
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StoreResult(pixelCoord, albedo * totalIrradiance / totalWeight);
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return;
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}
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[unroll]
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for (i = SSS_N_SAMPLES_FAR_FIELD, n = SSS_N_SAMPLES_NEAR_FIELD; i < n; i++)
|
|
{
|
|
// Integrate over the image or tangent plane in the view space.
|
|
EvaluateSample(i, n, profileID, iR, iP, pixelCoord + 0.5, cacheOffset,
|
|
shapeParam, centerPosVS, mmPerUnit, pixelsPerMm,
|
|
tangentX, tangentY, projMatrix,
|
|
totalIrradiance, totalWeight);
|
|
}
|
|
|
|
StoreResult(pixelCoord, albedo * totalIrradiance / totalWeight);
|
|
}
|