Find out 3D position of point on texture

Hello everybody!

I need to solve a very specific problem. Let’s have simply sphere and some texture (512x512) on it. And for some reason, I’m interested in point on texture with position 100x100 and now I need to know 3D position of that point. It’s obvious that point is lying somewhere on the sphere surface.

I hope It’s clear! If not I will attach some picture.

Thanks!
Karel

You mean something like that: