<CORE>/ShaderLibrary/Sampling/Sampling.hlsl full source
#ifndef UNITY_SAMPLING_INCLUDED
#define UNITY_SAMPLING_INCLUDED
#if SHADER_API_MOBILE || SHADER_API_GLES3 || SHADER_API_SWITCH || SHADER_API_SWITCH2 || defined(UNITY_UNIFIED_SHADER_PRECISION_MODEL)
#pragma warning (disable : 3205) // conversion of larger type to smaller
#endif
//-----------------------------------------------------------------------------
// Sample generator
//-----------------------------------------------------------------------------
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Sampling/Fibonacci.hlsl"
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Sampling/Hammersley.hlsl"
//-----------------------------------------------------------------------------
// Coordinate system conversion
//-----------------------------------------------------------------------------
// Transforms the unit vector from the spherical to the Cartesian (right-handed, Z up) coordinate.
real3 SphericalToCartesian(real cosPhi, real sinPhi, real cosTheta)
{
real sinTheta = SinFromCos(cosTheta);
return real3(real2(cosPhi, sinPhi) * sinTheta, cosTheta);
}
real3 SphericalToCartesian(real phi, real cosTheta)
{
real sinPhi, cosPhi;
sincos(phi, sinPhi, cosPhi);
return SphericalToCartesian(cosPhi, sinPhi, cosTheta);
}
// Converts Cartesian coordinates given in the right-handed coordinate system
// with Z pointing upwards (OpenGL style) to the coordinates in the left-handed
// coordinate system with Y pointing up and Z facing forward (DirectX style).
real3 TransformGLtoDX(real3 v)
{
return v.xzy;
}
// Performs conversion from equiareal map coordinates to Cartesian (DirectX cubemap) ones.
real3 ConvertEquiarealToCubemap(real u, real v)
{
real phi = TWO_PI - TWO_PI * u;
real cosTheta = 1.0 - 2.0 * v;
return TransformGLtoDX(SphericalToCartesian(phi, cosTheta));
}
// Convert a texel position into normalized position [-1..1]x[-1..1]
real2 CubemapTexelToNVC(uint2 unPositionTXS, uint cubemapSize)
{
return 2.0 * real2(unPositionTXS) / real(max(cubemapSize - 1, 1)) - 1.0;
}
// Map cubemap face to world vector basis
static const real3 CUBEMAP_FACE_BASIS_MAPPING[6][3] =
{
//XPOS face
{
real3(0.0, 0.0, -1.0),
real3(0.0, -1.0, 0.0),
real3(1.0, 0.0, 0.0)
},
//XNEG face
{
real3(0.0, 0.0, 1.0),
real3(0.0, -1.0, 0.0),
real3(-1.0, 0.0, 0.0)
},
//YPOS face
{
real3(1.0, 0.0, 0.0),
real3(0.0, 0.0, 1.0),
real3(0.0, 1.0, 0.0)
},
//YNEG face
{
real3(1.0, 0.0, 0.0),
real3(0.0, 0.0, -1.0),
real3(0.0, -1.0, 0.0)
},
//ZPOS face
{
real3(1.0, 0.0, 0.0),
real3(0.0, -1.0, 0.0),
real3(0.0, 0.0, 1.0)
},
//ZNEG face
{
real3(-1.0, 0.0, 0.0),
real3(0.0, -1.0, 0.0),
real3(0.0, 0.0, -1.0)
}
};
// Convert a normalized cubemap face position into a direction
real3 CubemapTexelToDirection(real2 positionNVC, uint faceId)
{
real3 dir = CUBEMAP_FACE_BASIS_MAPPING[faceId][0] * positionNVC.x
+ CUBEMAP_FACE_BASIS_MAPPING[faceId][1] * positionNVC.y
+ CUBEMAP_FACE_BASIS_MAPPING[faceId][2];
return normalize(dir);
}
//-----------------------------------------------------------------------------
// Sampling function
// Reference : http://www.cs.virginia.edu/~jdl/bib/globillum/mis/shirley96.pdf + PBRT
//-----------------------------------------------------------------------------
// Performs uniform sampling of the unit disk.
// Ref: PBRT v3, p. 777.
real2 SampleDiskUniform(real u1, real u2)
{
real r = sqrt(u1);
real phi = TWO_PI * u2;
real sinPhi, cosPhi;
sincos(phi, sinPhi, cosPhi);
return r * real2(cosPhi, sinPhi);
}
// Performs cubic sampling of the unit disk.
real2 SampleDiskCubic(real u1, real u2)
{
real r = u1;
real phi = TWO_PI * u2;
real sinPhi, cosPhi;
sincos(phi, sinPhi, cosPhi);
return r * real2(cosPhi, sinPhi);
}
real3 SampleConeUniform(real u1, real u2, real cosTheta)
{
float r0 = cosTheta + u1 * (1.0f - cosTheta);
float r = sqrt(max(0.0, 1.0 - r0 * r0));
float phi = TWO_PI * u2;
return float3(r * cos(phi), r * sin(phi), r0);
}
real3 SampleSphereUniform(real u1, real u2)
{
real phi = TWO_PI * u2;
real cosTheta = 1.0 - 2.0 * u1;
return SphericalToCartesian(phi, cosTheta);
}
// Performs cosine-weighted sampling of the hemisphere.
// Ref: PBRT v3, p. 780.
real3 SampleHemisphereCosine(real u1, real u2)
{
real3 localL;
// Since we don't really care about the area distortion,
// we substitute uniform disk sampling for the concentric one.
localL.xy = SampleDiskUniform(u1, u2);
// Project the point from the disk onto the hemisphere.
localL.z = sqrt(1.0 - u1);
return localL;
}
// Cosine-weighted sampling without the tangent frame.
// Ref: http://www.amietia.com/lambertnotangent.html
real3 SampleHemisphereCosine(real u1, real u2, real3 normal)
{
// This function needs to used safenormalize because there is a probability
// that the generated direction is the exact opposite of the normal and that would lead
// to a nan vector otheriwse.
real3 pointOnSphere = SampleSphereUniform(u1, u2);
return SafeNormalize(normal + pointOnSphere);
}
real3 SampleHemisphereUniform(real u1, real u2)
{
real phi = TWO_PI * u2;
real cosTheta = 1.0 - u1;
return SphericalToCartesian(phi, cosTheta);
}
void SampleSphere(real2 u,
real4x4 localToWorld,
real radius,
out real lightPdf,
out real3 P,
out real3 Ns)
{
real u1 = u.x;
real u2 = u.y;
Ns = SampleSphereUniform(u1, u2);
// Transform from unit sphere to world space
P = radius * Ns + localToWorld[3].xyz;
// pdf is inverse of area
lightPdf = 1.0 / (FOUR_PI * radius * radius);
}
void SampleHemisphere(real2 u,
real4x4 localToWorld,
real radius,
out real lightPdf,
out real3 P,
out real3 Ns)
{
real u1 = u.x;
real u2 = u.y;
// Random point at hemisphere surface
Ns = -SampleHemisphereUniform(u1, u2); // We want the y down hemisphere
P = radius * Ns;
// Transform to world space
P = mul(real4(P, 1.0), localToWorld).xyz;
Ns = mul(Ns, (real3x3)(localToWorld));
// pdf is inverse of area
lightPdf = 1.0 / (TWO_PI * radius * radius);
}
// Note: The cylinder has no end caps (i.e. no disk on the side)
void SampleCylinder(real2 u,
real4x4 localToWorld,
real radius,
real width,
out real lightPdf,
out real3 P,
out real3 Ns)
{
real u1 = u.x;
real u2 = u.y;
// Random point at cylinder surface
real t = (u1 - 0.5) * width;
real theta = 2.0 * PI * u2;
real cosTheta = cos(theta);
real sinTheta = sin(theta);
// Cylinder are align on the right axis
P = real3(t, radius * cosTheta, radius * sinTheta);
Ns = normalize(real3(0.0, cosTheta, sinTheta));
// Transform to world space
P = mul(real4(P, 1.0), localToWorld).xyz;
Ns = mul(Ns, (real3x3)(localToWorld));
// pdf is inverse of area
lightPdf = 1.0 / (TWO_PI * radius * width);
}
void SampleRectangle(real2 u,
real4x4 localToWorld,
real width,
real height,
out real lightPdf,
out real3 P,
out real3 Ns)
{
// Random point at rectangle surface
P = real3((u.x - 0.5) * width, (u.y - 0.5) * height, 0);
Ns = real3(0, 0, -1); // Light down (-Z)
// Transform to world space
P = mul(real4(P, 1.0), localToWorld).xyz;
Ns = mul(Ns, (real3x3)(localToWorld));
// pdf is inverse of area
lightPdf = 1.0 / (width * height);
}
void SampleDisk(real2 u,
real4x4 localToWorld,
real radius,
out real lightPdf,
out real3 P,
out real3 Ns)
{
// Random point at disk surface
P = real3(radius * SampleDiskUniform(u.x, u.y), 0);
Ns = real3(0.0, 0.0, -1.0); // Light down (-Z)
// Transform to world space
P = mul(real4(P, 1.0), localToWorld).xyz;
Ns = mul(Ns, (real3x3)(localToWorld));
// pdf is inverse of area
lightPdf = 1.0 / (PI * radius * radius);
}
// Solid angle cone sampling.
// Takes the cosine of the aperture as an input.
void SampleCone(real2 u, real cosHalfAngle,
out real3 dir, out real rcpPdf)
{
real cosTheta = lerp(1, cosHalfAngle, u.x);
real phi = TWO_PI * u.y;
dir = SphericalToCartesian(phi, cosTheta);
rcpPdf = TWO_PI * (1 - cosHalfAngle);
}
// Returns uniformly distributed sample vectors in a cone using
// "golden angle spiral method" described here: http://blog.marmakoide.org/?p=1
// note: the first sample is always [0, 0, 1]
real3 SampleConeStrata(uint sampleIdx, real rcpSampleCount, real cosHalfApexAngle)
{
real z = 1.0f - ((1.0f - cosHalfApexAngle) * sampleIdx) * rcpSampleCount;
real r = sqrt(1.0f - z * z);
real a = sampleIdx * 2.3999632297286f; // pi*(3-sqrt(5))
real sphi = sin(a);
real cphi = cos(a);
return real3(r * cphi, r * sphi, z);
}
#if SHADER_API_MOBILE || SHADER_API_GLES3 || SHADER_API_SWITCH || SHADER_API_SWITCH2
#pragma warning (enable : 3205) // conversion of larger type to smaller
#endif
#endif // UNITY_SAMPLING_INCLUDED