/*! Cosine weighted sphere sampling. Up direction is the z direction. */
inline direction_sample cosineSampleSphere(real u, real v) {
const real phi = two_pi<real>() * u;
const real vv = 2.0f * (v - 0.5f);
const real cosTheta = sign(vv) * sqrt(abs(vv));
const real sinTheta = cos2sin(cosTheta);
return direction_sample(directionFromPhiCosThetaSinTheta(phi, cosTheta, sinTheta), 2.0f * cosTheta * one_over_pi<real>());
}
/*! Uniform sampling of spherical cone. Cone direction is the z
* direction. */
inline direction_sample uniformSampleCone(real u, real v, real angle) {
const real phi = two_pi<real>() * u;
const real cosTheta = 1.0f - v * (1.0f - cos(angle));
const real sinTheta = cos2sin(cosTheta);
return direction_sample(directionFromPhiCosThetaSinTheta(phi, cosTheta, sinTheta),
1.f / (four_pi<real>() * sqr(sin(0.5f * angle))));
}
/*! Samples hemisphere with power cosine distribution. Up direction
* is the z direction. */
inline direction_sample powerCosineSampleHemisphere(real u, real v, real exp) {
const real phi = two_pi<real>() * u;
const real cosTheta = pow(v, 1.f / (exp + 1));
const real sinTheta = cos2sin(cosTheta);
return direction_sample(directionFromPhiCosThetaSinTheta(phi, cosTheta, sinTheta),
(exp + 1.0f) * pow(cosTheta, exp) * one_over_two_pi<real>());
}
/*! Samples the distribution. \param s is the sample location
* provided by the caller. */
inline Vec3fa AnisotropicBlinn__sample(const AnisotropicBlinn* This, const float sx, const float sy)
{
const float phi =float(two_pi)*sx;
const float sinPhi0 = sqrtf(This->nx+1)*sinf(phi);
const float cosPhi0 = sqrtf(This->ny+1)*cosf(phi);
const float norm = rsqrt(sqr(sinPhi0)+sqr(cosPhi0));
const float sinPhi = sinPhi0*norm;
const float cosPhi = cosPhi0*norm;
const float n = This->nx*sqr(cosPhi)+This->ny*sqr(sinPhi);
const float cosTheta = powf(sy,rcp(n+1));
const float sinTheta = cos2sin(cosTheta);
const float pdf = This->norm1*powf(cosTheta,n);
const Vec3fa h = Vec3fa(cosPhi * sinTheta, sinPhi * sinTheta, cosTheta);
const Vec3fa wh = h.x*This->dx + h.y*This->dy + h.z*This->dz;
return Vec3fa(wh,pdf);
}
/*! Uniform hemisphere sampling. Up direction is the z direction. */
inline direction_sample uniformSampleHemisphere(real u, real v) {
const real phi = two_pi<real>() * u;
const real cosTheta = v, sinTheta = cos2sin(v);
return direction_sample(directionFromPhiCosThetaSinTheta(phi, cosTheta, sinTheta), one_over_two_pi<real>());
}
/*! Uniform sphere sampling. */
inline direction_sample uniformSampleSphere(real u, real v) {
const auto phi = two_pi<real>() * u;
const auto cosTheta = 1 - 2 * v, sinTheta = cos2sin(cosTheta);
return direction_sample { directionFromPhiCosThetaSinTheta(phi, cosTheta, sinTheta), one_over_four_pi<real>() };
}