matte surface - bad sampling of background

[flipside]

Hi,

I have a problem with the vrayMtlWrapper. Here is a render with a background image, and a plane that covers the street with a vraymtl inside a vrayMtlwrapper. I've turned on matte surface and shadows.



If you look closely, you see the sampling of the background turns bad where the matte surface is placed.

Here the same image with the dmc samples turned on:


So there is no sampling going on on the matte plane.

Is this normal? Can it be solved?

Thanks,

wouter

[vlado]

This happens because, as requested by some users, V-Ray now considers the background as seen through matte objects as separate background (so that it is not affected by color mapping then the corresponding option is off) and not a part of the regular RGBA channel (which contains only the matte shadows). The side effect is V-Ray cannot do antialiasing on the background through matte objects, since it does not immediately "see" it.

This is corrected for future builds, but for the time being, you can do several things:

(*) Use fixed rate AA with higher Min. rate;
(*) Use brute force GI, dome light or something else that would cause the matte material to be sampled more accurately;
(*) Composite the background separately (probably the best thing to do);

Best regards,
Vlado

[flipside]

ok thanks vlado!