Inventor is a 3D toolkit built on top of OpenGL.
It provides a large set of classes for creating 3D scenes, and for creating interaction and animation.
It also defines a standard file format for 3D models (".iv").
The .iv format was used for the VRML 1.0 standard for web-based 3D.
The program ivview displays .iv models.
Inventor-based applications normally use the Inventor library's framework, instead of GLUT or other similar program frameworks.
However, one can use a subset of the Inventor classes specifically to render .iv models in any OpenGL program.