Burley subsurface sampled with wrong pdf?

Development Rendering
, ,
1

Hello.

I’m learning the implementation of subsurface scattering with Burley’s diffusion profile in UE.

In SubsurfaceBurleyNormalized.ush, in GenerateSampleInfo():

It looks like there’s a sample of radius and a sample of angle, but why the BurleySampleInfo.Pdf is 2piR(r)*r? Shouldn’t it be the R(r)*r since we sampled from both radius and angle?

In my understanding, if we only sample radius, then we use the 2piR(r)*r. But maybe I’m wrong.

Thanks for any response!