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#include "CoreRP/ShaderLibrary/Packing.hlsl"
#include "../DiffusionProfile/DiffusionProfileSettings.cs.hlsl"
#include "../DiffusionProfile/DiffusionProfile.hlsl"
// Subsurface scattering constant
#define SSS_WRAP_ANGLE (PI/12) // 15 degrees
#define SSS_WRAP_LIGHT cos(PI/2 - SSS_WRAP_ANGLE)
CBUFFER_START(UnitySSSAndTransmissionParameters)
// Warning: Unity is not able to losslessly transfer integers larger than 2^24 to the shader system.
// Therefore, we bitcast uint to float in C#, and bitcast back to uint in the shader.
uint _EnableSubsurfaceScattering; // Globally toggles subsurface and transmission scattering on/off
float _TexturingModeFlags; // 1 bit/profile; 0 = PreAndPostScatter, 1 = PostScatter
float _TransmissionFlags; // 1 bit/profile; 0 = regular, 1 = thin
// Old SSS Model >>>
float4 _HalfRcpVariancesAndWeights[DIFFUSION_PROFILE_COUNT][2]; // 2x Gaussians in RGB, A is interpolation weights
// <<< Old SSS Model
// Use float4 to avoid any packing issue between compute and pixel shaders
float4 _ThicknessRemaps[DIFFUSION_PROFILE_COUNT]; // R: start, G = end - start, BA unused
float4 _ShapeParams[DIFFUSION_PROFILE_COUNT]; // RGB = S = 1 / D, A = filter radius
float4 _TransmissionTintsAndFresnel0[DIFFUSION_PROFILE_COUNT]; // RGB = 1/4 * color, A = fresnel0
float4 _WorldScales[DIFFUSION_PROFILE_COUNT]; // X = meters per world unit; Y = world units per meter
CBUFFER_END
// ----------------------------------------------------------------------------
// helper functions
// ----------------------------------------------------------------------------
// 0: [ albedo = albedo ]
// 1: [ albedo = 1 ]
// 2: [ albedo = sqrt(albedo) ]
uint GetSubsurfaceScatteringTexturingMode(int diffusionProfile)
{
uint texturingMode = 0;
#if defined(SHADERPASS) && (SHADERPASS == SHADERPASS_SUBSURFACE_SCATTERING)
// If the SSS pass is executed, we know we have SSS enabled.
bool enableSss = true;
#else
bool enableSss = _EnableSubsurfaceScattering != 0;
#endif
if (enableSss)
{
bool performPostScatterTexturing = IsBitSet(asuint(_TexturingModeFlags), diffusionProfile);
if (performPostScatterTexturing)
{
// Post-scatter texturing mode: the albedo is only applied during the SSS pass.
#if defined(SHADERPASS) && (SHADERPASS != SHADERPASS_SUBSURFACE_SCATTERING)
texturingMode = 1;
#endif
}
else
{
// Pre- and post- scatter texturing mode.
texturingMode = 2;
}
}
return texturingMode;
}
// Returns the modified albedo (diffuse color) for materials with subsurface scattering.
// See GetSubsurfaceScatteringTexturingMode() above for more details.
// Ref: Advanced Techniques for Realistic Real-Time Skin Rendering.
float3 ApplySubsurfaceScatteringTexturingMode(uint texturingMode, float3 color)
{
switch (texturingMode)
{
case 2: color = sqrt(color); break;
case 1: color = 1; break;
default: color = color; break;
}
return color;
}
// ----------------------------------------------------------------------------
// Encoding/decoding SSS buffer functions
// ----------------------------------------------------------------------------
struct SSSData
{
float3 diffuseColor;
float subsurfaceMask;
uint diffusionProfile;
};
#define SSSBufferType0 float4
// SSSBuffer texture declaration
TEXTURE2D(_SSSBufferTexture0);
// Note: The SSS buffer used here is sRGB
void EncodeIntoSSSBuffer(SSSData sssData, uint2 positionSS, out SSSBufferType0 outSSSBuffer0)
{
outSSSBuffer0 = float4(sssData.diffuseColor, PackFloatInt8bit(sssData.subsurfaceMask, sssData.diffusionProfile, 16));
}
// Note: The SSS buffer used here is sRGB
void DecodeFromSSSBuffer(float4 sssBuffer, uint2 positionSS, out SSSData sssData)
{
sssData.diffuseColor = sssBuffer.rgb;
UnpackFloatInt8bit(sssBuffer.a, 16, sssData.subsurfaceMask, sssData.diffusionProfile);
}
void DecodeFromSSSBuffer(uint2 positionSS, out SSSData sssData)
{
float4 sssBuffer = LOAD_TEXTURE2D(_SSSBufferTexture0, positionSS);
DecodeFromSSSBuffer(sssBuffer, positionSS, sssData);
}
// OUTPUT_SSSBUFFER start from SV_Target2 as SV_Target0 and SV_Target1 are used for lighting buffer
#define OUTPUT_SSSBUFFER(NAME) out GBufferType0 MERGE_NAME(NAME, 0) : SV_Target2
#define ENCODE_INTO_SSSBUFFER(SURFACE_DATA, UNPOSITIONSS, NAME) EncodeIntoSSSBuffer(ConvertSurfaceDataToSSSData(SURFACE_DATA), UNPOSITIONSS, MERGE_NAME(NAME, 0))
#define DECODE_FROM_SSSBUFFER(UNPOSITIONSS, SSS_DATA) DecodeFromSSSBuffer(UNPOSITIONSS, SSS_DATA)
// In order to support subsurface scattering, we need to know which pixels have an SSS material.
// It can be accomplished by reading the stencil buffer.
// A faster solution (which avoids an extra texture fetch) is to simply make sure that
// all pixels which belong to an SSS material are not black (those that don't always are).
// We choose the blue color channel since it's perceptually the least noticeable.
float3 TagLightingForSSS(float3 subsurfaceLighting)
{
subsurfaceLighting.b = max(subsurfaceLighting.b, HALF_MIN);
return subsurfaceLighting;
}
// See TagLightingForSSS() for details.
bool TestLightingForSSS(float3 subsurfaceLighting)
{
return subsurfaceLighting.b > 0;
}