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Vray Shadow Matte not included in alpha - behind glass / refractive object


johnharrison
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Hello!

 

Im trying to do an interior archviz shot with a part of the exterior showing through the living room windows, but the shadow matte that Ive set up isn't being affected by the shadows when its behind the living room windows or to rephrase, its not visible in the alpha channel, which it should be. When I do arender outside the glass everything seems to be in order (see uploaded images). Does anyone have any ideas what Im doing wrong? It seems unlikely that this isnt in some way supported, right?

 

shadow matte exterior.jpg

 

shadow matte interior problem.jpg

 

shadow matte interior problem alpha.jpg

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That looks exactly like what I would expect.

 

If you want the ground to not be part of the alpha then you have to set its alpha contribution to -1 in the VRay Properties. But really, if you want everything you built to render and just want to make adjustments to the exterior furniture, then just render a Refraction Pass.

 

Am I not understanding the question?

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Hi, Corey. I will try to re-explain; the shadow matte seems to be set up correctly already with -1 alpha contribution, as you mention. The problem is that it only works when I DON'T render from behind the glass. When I render from my camera setup inside the apartment, you look through the living room windows, onto the exterior and onto the shadow matte, but the shadow matte isnt displayed right... In attachment image 1 you see its working fine, but in image 2 you see the shadow matte from behind a window and that's where it's not working. (completely solid white in alpha channel)

 

I know a solution would be to hide the glass and do a separate render, but there has to be a logical solution to this...

 

If anyone need any screenshots of anything, just let me know. I've already tried setting the glass material's refractive channel to "affect all", but that didnt work..

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I see.

 

I have had a similar issue rendering people passes for animations. I don't recall exactly the fix or if we ever even found one, but I think it had to do with the Generate/Recieve GI option. Maybe try there next.

 

Sorry that isn't much help, but it is my final thought on this. I hope someone else has your answer.

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Hey John...

 

If i have understood the problem, I will suggest using Object Vray Properties to set up a Matte Shadow Objects. There is problem in VrayMatteShadow Mtl with Reflections and Refractions. It has bugged me once and i never use Material for Matte Shadows.

 

Try it out.. Hope you get your results.

 

Thanks..

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