Open source high performance cross platform realtime 3D engine written in C++.
Ranked in these QuestionsQuestion Ranking
Pro Free and open source
Pro Good polymorphic design
If you are considering writing your own engine with openGL, you might want to consider Irrlicht instead. It makes many features of any engine worth its salt easy, including events, serialization, nodes, animators, materials, logging, and animation. Bring your own sound and networking.
Pro Easy to entry level C++ experience
If you want to start game developing with C++, then Irrlicht is a good candidate since it removes most of the complications in game making in C++. It will let you obtain experience in programming and games at the same time.
Especially if you compile it yourself, it can be very light in memory usage.
Pro Support for multiple formats
This engine supports multiple formats for 3D objects and textures.
Con Not a game engine
This is a 3D graphics engine similar to Ogre3D. Thus, it doesn't provide any pathfinding or physics support. Support for those will have to be added by the dev.
Obsolete over 5 years ago. While the engine is being worked on with plans for new features and support, the movement is slow, leaving many engines far more advanced in certain areas.