Ogre Team company

 OGRE (Object-Oriented Graphics Rendering Engine) is a scene-oriented, flexible 3D engine written in C++ designed to make it easier and more intuitive for developers to produce applications utilising hardware-accelerated 3D graphics. The class library abstracts all the details of using the underlying system libraries like Direct3D and OpenGL and provides an interface based on world objects and other intuitive classes.

 OGRE does not assume what type of game or demo you want to make. It uses a flexible class hierarchy allowing you to design plugins to specialise the scene organisation approach taken to allow you to make any kind of scene you like. Want to render indoor levels fast? Fine, use the BSP/PVS plugin scene manager which has already been written. Want an outdoor landscape? Again, use another plugin scene manager. The rest of the engine continues to function exactly as before.