PreRendering Glass Refractions, is it possible?

[SunGlare]

I'm attempting to render wonderful chandelier, custom made from thousands various glass bubbles. Rendering time goes through the roof, obviously, but is there outthere somewhere a technique to prerender the whole thing and then comp it back... or I'm just wanderer in the dark.

 

I've already grouped those babies into random nests, and repeated as vray proxy, but refraction is not about memory, its pure cpu.

 

The chandelier sits in the middle of room, pretty low, so it reflect in itself whole room, and refracts behind scene (incl. glass bubbles).

 

My Sets are: Quadcore, 8GB, Quadro512

Vray: glass: refl/refr: subdiv 4, refr limit:10

 

I know some 3d, but I've been out for a while and maybe there is some new approach to this. Help.

 

Thanks for Input, Thanks for reading.

[BrianKitts]

you can't really pre-render just the refractions, but you could texture bake the entire object.

[Crazy Homeless Guy]

You could render the object in a separate pass, and then comp it. I do this all the time with complex materials that have a lot of glossiness. Scroll down to where it explains matte in the list. I typically set the alpha contribution of the matte objects to -1.

 

http://www.spot3d.com/vray/help/150SP1/global_settings.htm

 

Then, switch the material on the object for a simple material, and render the rest of the scene. Combine the two passes in photoshop, and use a layer defringe if necessary.

[SunGlare]

Thanks, I'll give it a try.

Below is small example of how this will(I hope) look like, but this one has lot less glass elements than what I have on mind(and mesh)

 

Thanks again for the mask object idea.

I'll post test results shortly.

[Tommy L]

Well glass shouldnt pose too much of a problem with Vray. Its a superfast raytracer. If you disable glossies, you should be able to render it pretty quick, then re-render your scene with the object disabled and glossies on. Comp the two together and your all good. Unless you want to use caustics of course, then its a whole new ballgame.