I'm using THREE.js to render my scene and I got a tricky question - how can I get the color of a specific point on a geometry face? 

By color, I don't mean the face or material color, I mean the actual output color at the specific point, based on: material, face color AND texture color at the specific location. for example, if the texture on the face at given point is red, and the material color is half visible (alpha = 0.5), what I expect to get is: (r=1.0, g=0.0, b=0.0, a=0.5).

Note: performance is important.

Any ideas?
Thanks!