void testCosineHalfSphere()
{
Plot2D plot_down_z( output_path + "/cosine_half_sphere__down_z.png", plot_size, plot_size );
Plot2D plot_down_y( output_path + "/cosine_half_sphere__down_y.png", plot_size, plot_size );
Plot2D plot_rot( output_path + "/cosine_half_sphere__rot.png", plot_size, plot_size );
Transform xform = makeRotation( 0.5, Vector4( 1.0f, 1.0f, 1.0f ) );
Vector4 v, rot;
for( auto i = 0; i < points_per_plot; i++ ) {
rng.cosineUnitHalfSphere( v );
plot_down_z.addPoint( v.x, v.y );
plot_down_y.addPoint( v.x, v.z );
rot = mult( xform.fwd, v );
plot_rot.addPoint( rot.x, rot.y );
}
}
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;
}
