DistributionSample Material::sampleCosineLobe( RandomNumberGenerator & rng,
const RayIntersection & intersection ) const
{
DistributionSample sample;
// FIXME: There must be a faster way
// Generate an arbitrary direction to help us make a basis for tangent space.
// The likelyhood that this is pointing in the same direction as the normal is very low.
Vector4 elsewhere; rng.uniformVolumeUnitCube(elsewhere);
Vector4 tangent = cross(elsewhere, intersection.normal).normalized();
Vector4 bitangent = cross(intersection.normal, tangent).normalized();
// Randomly generate a direction from a cosine-weighted pdf centered about the normal
Vector4 R; rng.cosineUnitHalfSphere(R);
sample.direction = R.x * tangent + R.y * bitangent + R.z * intersection.normal;
sample.direction.makeDirection();
sample.pdf_sample = dot(sample.direction, intersection.normal) / M_PI;
//sample.pdf_sample *= M_PI; // TEMP - FIXME - this shouldn't be here
sample.pdf_sample *= 2.0 * M_PI; // TEMP - FIXME - this shouldn't be here
return sample;
}
