The OpenSceneGraph is an OpenSource, cross-platform graphics toolkit for the development of high-performance graphics applications such as flight simulators, games, virtual reality and scientific visualization.
It is based around the concept of a SceneGraph, providing an object-oriented framework on top of OpenGL. This frees the developer from implementing and optimizing low-level graphics calls and provides many additional utilities for rapid development of graphics applications.
Written entirely in Standard C++ and OpenGL it runs on all Windows platforms, OSX, GNU/Linux, IRIX, Solaris, HP-Ux, AIX and FreeBSD operating systems.
The official OpenSceneGraph homepage is at [L1 ]
A good introduction to OSG is the Quick Start Guide [L2 ]