= Assignment 4 Discussion =

Don't hesitate to ask questions.

Q1: The first question says "L(phi, theta) = cos(theta) when theta > PI/2 and L(phi, theta) = 0 otherwise."  Shouldn't this be for theta < PI/2, so that it's cosine-weighted hemisphere sampling, which is more appropriate here?  If theta > PI / 2, the arrangement doesn't make much sense - the luminance would be negative!  And Shouldn't we also be weighting by the cos(theta) term in the radiance function (or is this already implied)?

I agree (PaulTarjan)

=== A1: ===

It should be {{{theta < PI/2}}}.  It was a mistake in the assignment and has now been fixed.  The intent of the question was for you to sample with respect to {{{L = cos(theta)}}}, which is exactly what {{{infinitesample.cpp}}} does.  However, it is true that the integral you are estimating does contain an additional term {{{cos(theta)}}}.  In this case, it is possible to analytically sample with respect to more than just the value of {{{L}}}.  If you choose to do this, please state so explicitly.


Q2: I've extracted the "string sample" parameter from the paramter set in directlighting.cpp, but how do I access this data when I'm doing the re-weighting in transport.cpp? Can I just cast around the Light * object? (BillDwyer)