Add missing maximum depth check to VolPathIntegrator
Add missing maximum depth check to VolPathIntegrator

We were only terminating paths due to hitting the maximum depth at surface interactions(!).

mmp/pbrt-v3,nyue/pbrt-v3,Vertexwahn/pbrt-v3,shihchinw/pbrt-v3,bssrdf/pbrt-v3,Vertexwahn/pbrt-v3,Vertexwahn/pbrt-v3,mmp/pbrt-v3,shihchinw/pbrt-v3,nispaur/pbrt-v3,mmp/pbrt-v3,mwkm/pbrt-v3,ambakshi/pbrt-v3,mwkm/pbrt-v3,nyue/pbrt-v3,nispaur/pbrt-v3,nyue/pbrt-v3,shihchinw/pbrt-v3,shihchinw/pbrt-v3,bssrdf/pbrt-v3,nyue/pbrt-v3,ambakshi/pbrt-v3,nispaur/pbrt-v3,ambakshi/pbrt-v3,nispaur/pbrt-v3,mmp/pbrt-v3,bssrdf/pbrt-v3