Why do we not apply Russian roulette also to the direct lighting?
ak-47
I'm confused...what is the difference between terminateProbability and f.rho?
mchoquet
@PandaX russian roulette is a way to sample arbitrary-length paths. Direct lighting is a length-1 path (you either reach the light or there's something in the way), so we don't need to use monte carlo for it.
@ak-47 rho is the percentage of light that would be reflected along the sample direction, and is defined over [0, 1]. We use this to choose a terminate probability according to the following rule: the more light would reflect, the more worthwhile it would be to trace this new ray, so the less likely we should be to terminate the path here. If 0% of the light reflects (rho = 0) then we should terminate with 100% probability, because no amount of light traveling along the new ray will change the amount of color we return.
Why do we not apply Russian roulette also to the direct lighting?
I'm confused...what is the difference between terminateProbability and f.rho?
@PandaX russian roulette is a way to sample arbitrary-length paths. Direct lighting is a length-1 path (you either reach the light or there's something in the way), so we don't need to use monte carlo for it.
@ak-47 rho is the percentage of light that would be reflected along the sample direction, and is defined over [0, 1]. We use this to choose a terminate probability according to the following rule: the more light would reflect, the more worthwhile it would be to trace this new ray, so the less likely we should be to terminate the path here. If 0% of the light reflects (rho = 0) then we should terminate with 100% probability, because no amount of light traveling along the new ray will change the amount of color we return.