Invisible objects troubles...

[cokuarq]

Hello everybody,

 

I have a problem with the invisiblity of objects in a scene.

I have a scene made of a building and trees where i want to have possibly two different passes. One pass should contain the building and the shadows of the trees (without the trees), menawhile the other should contain the trees only. I already tried the standard procedure : i make "invisible to camera" all the trees (vray proxies) preserving the shadow and the second pass i render the trees while everythig else is matte.

Any way i came to some trouble, strange black artefacts during the first pass, black spots (appear during the GI caluclation and persits on all render elements - Vray Diffuse, Vray Alpha, Vray Zdepth and so on) which affects some portions of the scene. I guess it is a bug or something because it affects only some limited areas of the render and the trees are the all the same proxy repeated, so the problem is not the proxy by itself.

I tried to look for a "invisible object" option to activate of the vray options but i couldn't find anything except the "matte" panel which doesn't work for me.

Do you have any suggestion how to resolve this problem or if there is a different way of doing the job?!

Thank you