Vray ObjectID

While doing research about vray's ObjectID, I stumbled across a post on "djx blog" (by David Johnson) about how he is using vray ObjectID's to create his matte passes. I wrote up a reply to his post (he ended his write-up asking readers to share how we use ObjectID's) and thought that it might be good to also post my reply here, for those who are still following my blog. :) Hopefully someone else also finds this useful!

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I have also been using vray for maya at work since about a year ago, I just thought that you might be interested to hear about the technique that I use when setting up my mattes.

If I'm going to use the Object ID's, I'll use vray's "object properties" node. It's found under "Create> vRay> apply single/multiple object properties node to selection." This allows me to apply object ID's to multiple geometries at once rather than 'adding vray attributes' to geometry one at a time. Also, in case you already have objectID attributes on a 'per-geometry' basis, the objectProperties node will override the existing objectID's.

Since geometry can (currently, as far as I know) only be part of one "object properties" node at once, you can then use the material ID's to further sort out your geo, say if you want a geometry to be in 'multimatte1', and 'multimatte2'

In order to have the render element distinguish between using the materialID versus the objectID, just check (or uncheck, accordingly) the box labeled "Use Material IDs" under the "Extra VRay Attributes" rollout in the multimatte attributes.
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I'm also curious to hear from anyone else using similar techniques in vray for maya, feel free to comment here or on the djx blog!

-cheers!