Panda3D is a game engine, a framework for 3D rendering and game development for Python and C programs. Panda3D is Open Source and free for any purpose, including commercial ventures, thanks to its liberal license.
Panda was created for commercial game development, and its primary users are still commercial game developers. Because of this, Panda3D needs to emphasize four areas: power, speed, completeness, and error tolerance. Everyone knows what power and speed are. But completeness and error tolerance deserve some extra commentary.
