Glass Material--Reflect on back side???

V-Ray V-Ray Common Render Theory
1

Hi All,

Please forgive my lack of basics, but should a physically realistic Glass Material have ‘Reflect on back side’ checked ON???

I understand this will get added to the max reflections/refraction so I need to take that into account, but will it be more realistic?? will it cause any issues apart from a longer render time??

Thanks again

2

IT should, AFAIK. Take a look at the reflection from a slightly off-center angle for a sheet of glass - you can usually see both reflections, the one from the “front” and the one from the “back”. This is all affected by the IOR and fresnel effect, so the backside reflection often appears much weaker. But the backside (inside?) of a pane of glass most definitely reflects.

Cheers,

Jorge

3

Thanks Voxel3d!

Do you find it affects render time much???
I guess it would depend on the scene a lot?

Cheers
jamie

4

Well it would, if you think about it it will double the number of rays traced (although I’m sure vray’s adaptive engine takes care of a lot of that).

IMHO you shouldn’t really do this (enable backside reflections) unless you need it for a specific reason since it’s effect is not going to be noticeable 99% of the time (for architectural rendering). If you’re doing product visualization involving lots of glass containers or what not then it might add that extra bit of realism I reckon.

Cheers!

Jorge