Spectrum DiffuseAreaLight::Sample_Le(const Point2f &u1, const Point2f &u2,
Float time, Ray *ray, Normal3f *nLight,
Float *pdfPos, Float *pdfDir) const {
ProfilePhase _(Prof::LightSample);
// Sample a point on the area light's _Shape_, _pShape_
Interaction pShape = shape->Sample(u1, pdfPos);
pShape.mediumInterface = mediumInterface;
*nLight = pShape.n;
// Sample a cosine-weighted outgoing direction _w_ for area light
Vector3f w;
if (twoSided) {
Point2f u = u2;
// Choose a side to sample and then remap u[0] to [0,1] before
// applying cosine-weighted hemisphere sampling for the chosen side.
if (u[0] < .5) {
u[0] = std::min(u[0] * 2, OneMinusEpsilon);
w = CosineSampleHemisphere(u);
} else {
u[0] = std::min((u[0] - .5f) * 2, OneMinusEpsilon);
w = CosineSampleHemisphere(u);
w.z *= -1;
}
*pdfDir = 0.5f * CosineHemispherePdf(std::abs(w.z));
} else {
w = CosineSampleHemisphere(u2);
*pdfDir = CosineHemispherePdf(w.z);
}
Vector3f v1, v2, n(pShape.n);
CoordinateSystem(n, &v1, &v2);
w = w.x * v1 + w.y * v2 + w.z * n;
*ray = pShape.SpawnRay(w);
return L(pShape, w);
}
void DiffuseAreaLight::Pdf_Le(const Ray &ray, const Normal3f &n, Float *pdfPos,
Float *pdfDir) const {
ProfilePhase _(Prof::LightPdf);
Interaction it(ray.o, n, Vector3f(), Vector3f(n), ray.time,
mediumInterface);
*pdfPos = shape->Pdf(it);
*pdfDir = twoSided ? (.5 * CosineHemispherePdf(AbsDot(n, ray.d)))
: CosineHemispherePdf(Dot(n, ray.d));
}
void Gen_CosHemisphere(BSDF* bsdf, const Vector3f& wo, Vector3f* wi, Float* pdf,
Spectrum* f) {
float u1 = rng.UniformFloat();
float u2 = rng.UniformFloat();
Vector3f wiL = CosineSampleHemisphere(Point2f(u1, u2));
*wi = bsdf->LocalToWorld(wiL);
float cosTheta = wiL.z;
*pdf = CosineHemispherePdf(cosTheta);
*f = bsdf->f(wo, *wi);
}
void Gen_CosHemisphere(BSDF* bsdf,
const Vector & wo, Vector* wi, float* pdf, Spectrum* f)
{
float u1 = rng.RandomFloat();
float u2 = rng.RandomFloat();
Vector wiL = CosineSampleHemisphere(u1, u2);
*wi = bsdf->LocalToWorld(wiL);
float cosTheta = wiL.z;
*pdf = CosineHemispherePdf(cosTheta, u2);
*f = bsdf->f(wo, *wi);
}
Spectrum DiffuseAreaLight::Sample_Le(const Point2f &u1, const Point2f &u2,
Float time, Ray *ray, Normal3f *nLight,
Float *pdfPos, Float *pdfDir) const {
Interaction pShape = shape->Sample(u1);
pShape.mediumInterface = mediumInterface;
Vector3f w = CosineSampleHemisphere(u2);
*pdfDir = CosineHemispherePdf(w.z);
// Transform cosine-weighted direction to normal's coordinate system
Vector3f v1, v2, n(pShape.n);
CoordinateSystem(n, &v1, &v2);
w = w.x * v1 + w.y * v2 + w.z * n;
*ray = pShape.SpawnRay(w);
*nLight = pShape.n;
*pdfPos = shape->Pdf(pShape);
return L(pShape, w);
}
Spectrum DiffuseAreaLight::Sample_Le(const Point2f &u1, const Point2f &u2,
Float time, Ray *ray, Normal3f *nLight,
Float *pdfPos, Float *pdfDir) const {
// Sample a point on the area light's _Shape_, _pShape_
Interaction pShape = shape->Sample(u1);
pShape.mediumInterface = mediumInterface;
*pdfPos = shape->Pdf(pShape);
*nLight = pShape.n;
// Sample a cosine-weighted outgoing direction _w_ for area light
Vector3f w = CosineSampleHemisphere(u2);
*pdfDir = CosineHemispherePdf(w.z);
Vector3f v1, v2, n(pShape.n);
CoordinateSystem(n, &v1, &v2);
w = w.x * v1 + w.y * v2 + w.z * n;
*ray = pShape.SpawnRay(w);
return L(pShape, w);
}
void DiffuseAreaLight::Pdf_Le(const Ray &ray, const Normal3f &n, Float *pdfPos,
Float *pdfDir) const {
Interaction it(ray.o, n, Vector3f(), Vector3f(n), ray.time, mediumInterface);
*pdfPos = shape->Pdf(it);
*pdfDir = CosineHemispherePdf(Dot(n, ray.d));
}
