Hey all,
Unfortunately depth attenuation in the Trace VOP doesn't work in PBR. In case anyone ever needs depth attenuation in glass in PBR, I use this cheap hack: I modified the glass material to include a gather loop that returns the depth of the glass at a sampling point, and I mix in the attenuation color with the refraction depending on that depth.
Limitations are mainly backlighting and the incredibly cheap VOP hackery .
cheers,
Abdelkareem
pbr_cheap_att.hipnc