Open Inventor is an object oriented scene graph library implemented in
C++ layered on top of OpenGL. It was originally developed by SGI.

Open Inventor(TM) is an object-oriented 3D toolkit offering a
comprehensive solution to interactive graphics programming problems.
It presents a programming model based on a 3D scene database that
dramatically simplifies graphics programming. It includes a rich set of
objects such as cubes, polygons, text, materials, cameras, lights,
trackballs, handle boxes, 3D viewers, and editors that speed up your
programming time and extend your 3D programming capabilities.