Black artifacts when using matte objects

[dmb_85]

Hi, first post here. Im just a noob in the realm of vray and 3d in general so bear with me.

 

I am trying to render an animation of a train in a forest. I am rendering the train seperate from the terrain, because I only want GI on the train. So far so good.

 

My problem comes in when I'm compositing the train with everything else. The train renders with these 'black sparkles' - hard-edged, black artifacts that show up all over the frame. They seem to be concentrated around my Vray proxy objects in particular, but a few show up in random places like the sky.

 

When rendering the train, I have everything except the train set as a matte object, alpha contribution -1.0, shadows and affect alpha checked.

 

Take a look at the attached image - I've circled the artifacts in red.

[Mechadus]

Without looking at the scene or raw frames themselves, I would say that looks more like color-mapping sparkles than a matte problem... Do you have 'Sub-pixel Mapping' checked on under the color mapping rollout in Vray?

 

-Nick

[dmb_85]

sub-pixel mapping was not checked - I tried rendering a single frame with it checked, and the black sparkles still appeared.

 

Any ideas?