Hi,
I have a lot of proxy (trees with opacity map) that I want to render with invisible to camera in Object Properties. When I render, I have some artefacts. I know that you can have problems with opacity so I raise Max Transp. levels to 100.
But that seems it’s not enough 
I try with 1000 (!) - the most higher possible value and it’s not yet enough.
Is there a way to solve that problem ? Can I have to go to refraction instead of opacity ?
Thx
I understand the fact that it’s a bit tricky (because trees are just invisible to camera but always there for GI). I thought to uncheck “generate GI”/“Recieve GI” - “Visible to GI” without result
My goal is simple, I need those trees for shadows, GI (it would be cool but not absolutely necessary) but not visible, How can I achieve this ?
ok ! I’m sure now it’s not the way to do.. So I decided to render one pass without treeproxies and another one with just treeproxies + matte object… It’s not exactly what I want but it’s ok.
It’s me or I’m a bit alone here… End of my “personal post” !! sorry for that ! 
Anyway, if someone have a trick…