shadow passes for integrating into live action

[shadevfx]

Hey Vray people.

What is the best way to set up a shadow/GI contact shadow type of pass to add back into a live action plate.

So far, we have some match modeled geo, with the plate projected onto the geo. The geo has primary vis off. In our beauty, this works great and our objects can reflect and get bounce off the hidden contact geo.

For the shadow scene however, we made our asset primary vis off, and the match models are visible. I have both a shadow, and a matte shadow render element, and neither give the subtle variations in intensity which is most likely due to the lack of GI shadowing. This "works", but really doesn't give me all V-Ray has to give.

I've also tried adding the match models to a properties node with "matte object" selected, affect alpha selected, shadows selected, etc... it also gives strange results. Definitely not the same as what we'd get in the beauty.

How are you guys going about this? Is there a more standard workflow I'm unaware of that would help?

Thanks,
Bryan

[vlado]

Normally you will make the object a matte object from the V-Ray Object Settings, set the alpha contribution to -1, and turn on the "Shadows" and "Affect shadows" optons.

There is also another important option, "No GI on other mattes", that controls how one matte object affects other matte objects.

From my simple tests, this works fine. If you have any problems, it would be best to get us a scene to vraymaya@chaosgroup.com

Best regards,
Vlado