First of all sory about my broken english.
Seccond: You can use OpenGL for calculations.
1.You need to create OpenGL hardware accelerated rendering context. Be careful. You may create slow software rendering context.
2.You must learn something about OpenGL matrix operations.
3.Precision is not important about computer vision. 3D accelerators are very strong in matrix computations. In computer vision you may chose “matrix oriented” algoritms in first few stages. But very hard work for computer is in identification of objects. This a database or AI problem. Sory, my knowlage in computer vision is not very big. But if you are needing of fast matrix computations without big precision
you can find some examples on www.opengl.org and learn some more from SDK help .