3D Portrait?

I’m trying to create an effect like the 3d portraits in dota 2 where I have a 3d model (example below) with animation that is shown but has some portions of it clipped by a frame. I thought to perhaps use multiple cameras but I couldn’t figure out a way when it needs to appear to be on top of something (for example the portrait on the left in the below image).

Any ideas on how to achieve this effect?

Edit: Ah I think I figured it out, just a matter of playing with the normalized viewport rectangles.

Yep your right, and don’t forget to use culling masks and clear flags to ensure your camera only draws the 3D portrait, good luck!