Hi,

I'm struggling to wrap my head around the issue of non-symmetric scattering in bdpt due to specular refraction. I thought about this for a long time and I am still not convinced if it is really a problem. I mean I do know that a specular refractive material is not symmetric if you swap the light source and the camera, but I don't see how it is non-symmetric when you trace from different point of view (i.e. camera and light source).

Does anybody have an intuitive explanation to this? (This is a question for you lyc )

Thank you.