Reflection through refraction ?

[rikou]

Hello,

I have a room surrounded by cylinder with background map.
I have a few items inside that room that reflects this cylinder ... Everything is ok. Now I just want to be able to keep all the reflections, but don't want to see anymore my cylinder through my glass windows to keep my background black with alpha.
The cylinder is not visible to camera and I set it to not visible to refraction, the problem is I lose the reflections inside my room.
If I keep it visible to camera but not visible to refraction, again, I lose the reflections inside my room.
So I put my cylinder to Matte object / Apha contribution to -1.
But ! To be more precise, the fact is that I have several glass layer so my alpha through these glass layer is not really "pure" (my refraction is something like 245/245/245). The fact is I can see my cylinder through my glass !


I would like to keep my cylinder not visible through the glass but visible in reflection for my items inside the room


What is the best way to do that ?
Any advices ?



Thanks in advance

[Zdravko.Keremidchiev]

I'm not sure you can do that in one pass. Even if you exclude the cylinder from the window refraction (VRayProperties) the room objects actually reflect the window refraction it self. You can do it in two passes instead. For the second pass you can use render mask and render only the windows.

[rikou]

Thanks !
I ended up using VrayOverrideMtl with the VrayMtl with my background map (A) in Reflect mtl slot and a full refractive VrayMtl (B) in Refract mtl slot.
Thereby, I have my room objects with reflection from my cylinder with background map (A) which is itself invisible to refraction (B)

[Svetlozar Draganov]

Glad to hear you've figured it out and thanks for the sharing.