Using Cycles, for a cartoony animation character I need spikes to be seen only from the character's edges and behind the character but never seen in facing angles. I want to avoid having to render the scene twice to be composited after.
For example: 2 meshes, 1 skin color, smooth, rigged, 1 blue spiky mesh sticking out, rigged, never seen in front.
I have no idea how to accomplish this.
Do I have to account for camera angle and normals of the spike's base?
Can I just layer one over the other with nodes?
Approximate Desired result done in Photoshop.