Light_SampleRes PointLight_sample(const Light* super,
const DifferentialGeometry& dg,
const Vec2f& s)
{
const PointLight* self = (PointLight*)super;
Light_SampleRes res;
// extant light vector from the hit point
const Vec3fa dir = self->position - dg.P;
const float dist2 = dot(dir, dir);
const float invdist = rsqrt(dist2);
// normalized light vector
res.dir = dir * invdist;
res.dist = dist2 * invdist;
res.pdf = inf; // per default we always take this res
// convert from power to radiance by attenuating by distance^2
res.weight = self->power * sqr(invdist);
const float sinTheta = self->radius * invdist;
if ((self->radius > 0.f) & (sinTheta > 0.005f)) {
// res surface of sphere as seen by hit point -> cone of directions
// for very small cones treat as point light, because float precision is not good enough
if (sinTheta < 1.f) {
const float cosTheta = sqrt(1.f - sinTheta * sinTheta);
const Vec3fa localDir = uniformSampleCone(cosTheta, s);
res.dir = frame(res.dir) * localDir;
res.pdf = uniformSampleConePDF(cosTheta);
const float c = localDir.z;
res.dist = c*res.dist - sqrt(sqr(self->radius) - (1.f - c*c) * dist2);
// TODO scale radiance by actual distance
} else { // inside sphere
const Vec3fa localDir = cosineSampleHemisphere(s);
res.dir = frame(dg.Ns) * localDir;
res.pdf = cosineSampleHemispherePDF(localDir);
// TODO:
res.weight = self->power * rcp(sqr(self->radius));
res.dist = self->radius;
}
}
return res;
}
Light_SampleRes DirectionalLight_sample(const Light* super,
const DifferentialGeometry& dg,
const Vec2f& s)
{
const DirectionalLight* self = (DirectionalLight*)super;
Light_SampleRes res;
res.dir = self->frame.vz;
res.dist = inf;
res.pdf = self->pdf;
if (self->cosAngle < COS_ANGLE_MAX)
res.dir = self->frame * uniformSampleCone(self->cosAngle, s);
res.weight = self->radiance; // *pdf/pdf cancel
return res;
}
/*! Uniform sampling of spherical cone. Cone direction is provided as argument. */
inline direction_sample uniformSampleCone(real u, real v, real angle, const real3& N) {
direction_sample s = uniformSampleCone(u, v, angle);
return direction_sample(frameZ(N) * s.value(), s.density());
}
