This is a question that''s been pondering in my mind for a while. Noticing all the 3D modelling programs (i.e. Blender, Maya, Soft Image), what API do they use to develop them? Is it a proprietary one, is it OpenGL, which is it?
I agree, they probably use OpenGL or some other realtime rendering API when you edit and model... When you render the final image, I think they''ve written a proprietary rendering engine... To calculate more precisely, with more effects, more options... That''s also why it takes so long to render with 3d modelling programs... It''s (mostly) software rendering, not hardware accelerated. OpenGL is engineered to be fast, not beautiful and detailed...
For real time rendering: Blender uses OpenGL. Maya probably uses OpenGL, since it can run outside of Windows. 3D Studio Max can use Direct3D or OpenGL (it''s been a while since I''ve had a chance to use it, correct me if I''m wrong ). I''ve never used SoftImage or seen used.
For final rendering they all use a custom renderer. That''s how you get the nice perpixel lighting, reflections, dozens of lights, shadows, bump mapping, and other things that 3D accelerator cards don''t always support.