FreeWRL is an Open Source, crossplatform VRML2 and X3D compliant browser, with script, SAI and EAI support. Platforms supported: Linux and other Unix-style platforms; Mac OS/X; Windows. Support for mobile platforms (iOS, Android, QNX) is under development.
SGL is a cross-platform, C++, scene graph API for real-time visualization (e.g., vis-sim, gaming, scientific modelling, GIS apps). It manages all the data needed to render a 3D scene using OpenGL.