Open Scene Graph

Open Scene Graph:
Based On OpenGL with MultiCore Processing and Clustering.
http://www.openscenegraph.org/projects/osg

Open Scene Graphs's Supported Formats:
http://www.openscenegraph.org/projects/osg/wiki/Support/UserGuides/Plugins

OpenSG: Also called Open Scene Graph which is a totally different Open Scene Graph, code base, and open source project than the one above. OpenSG has a better Scenegraph than the one above because it is multi-threaded and clustered throughout. However there is less development for OpenSG than the one above and direction on OpenSG seems to be poor at the moment. Both have their respective strenghts as a for instance the one above has KD-Trees, an Internal Database System, GIS, PPU (Post Processing Unit), and Bone Animation System.
http://opensg.vrsource.org/trac