Diffuse and specular contribution for plastic
Diffuse and specular contribution for plastic

Uses russian roulette to determine the BRDF to sample
Roulette is based on the luminance of the BRDF's rho() function, finding a better heuristic is probably a TODO..

szellmann/visionaray,ukoeln-vis/ctpperf,tu500/visionaray,szellmann/visionaray,ukoeln-vis/ctpperf,tu500/visionaray