I'm not quite sure I understand what you are asking about. Do you mean like taking a 3D sphere object and rendering it as a 2D circle image? I know a few CAD programs have this ability, for instance SolidWorks has it so that you can design in 3D and it can render as a 2D drawing.

Or do you mean like... switching from 3D camera view to something like a side view, front view, and get a somewhat 2D-ish look?