ArcBalls

Hey, I''m having trouble creating an arcball class... I need it to have: * a vector that has the position of the object in space, and the center of the camera (the same point). * a float which defines the radius of the arcball... I''ve looked into the DirectX SDK''s ArcBall class but there the arcball creates a world matrix, not a view matrix, I need it to generate a view atrix without effecting the object''s transform... Another thing, I need it to be able to translate the center of the object relative to the current view, let''s say, when the user drags the right mouse button, he will move the entire arcball...