- Posts: 12
- Joined: Fri Feb 20, 2015 5:55 am
- Location: Ukraine
Your' looking for matte channels, and this can be done by object ID or material ID. This will generate the 'ID" that 2D tools can use as a 'mask'
That beings said, there is no substitute for render passes, even in top 3D applciations, you will never get a better result in isolating the tire then rendering it out as a pass on its own.
Try building a couple of simple objects, give each their own Ojbect ID (use override) and within the object, create multiple material IDs (this can be on a 'group' of tools, not just a single)
The 3D render will now have 2 levels of selection for the pixels in the render.
As far as the alpha channel issue, I am a bit confused as to what your asking, but it sounds like you want to copy an alpha from one part of your comp to other tools somewhere else.
You can do that using either the 'matte' node with copy alpha, or boolean node to copy alpha from one to another.
I would be curious to see an example of is the real issue using a few simple tools.