Object Mask


So. I come from a compositing and photoshop background. Is there anyway to create a live mask with objects in blender?

For example, let’s say I have two circles (black circle and the other circle):

I only want the green portion of the second circle to show. In AE I would just use the alpha matte of the circle to hide the red portion of the circle.

Any idea of how to achieve this effect? Please let me know or point me in the right direction, I’m not even sure what terms to google for this within blender. Thanks!

If you mean in 3D on Meshes, you can achieve something similar with the Boolean-Modifier.

If you mean in 2D on already Rendered stuff, you would go with the composite Nodes.

Could you clarify what you want to do in more detail please?