BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
Coin is an implementation of Open Inventor. Open Inventor is the de facto standard API for retained-mode 3D graphics programming. Open Inventor has a highly extensible design, and has been designed to allow for rapid development of highly interactive 3D graphics applications in the fields of CAD, engineering, scientific computing, simulation, VRML, and visualization.
The Interreality project is a collection of Open Source, Free Software projects based on the Virtual Object System (VOS) platform. The goal is to develop a free and open platform for multi-user 3D virtual reality games, applications, and interactive, collaborative 3D virtual spaces. VOS is a powerful and generic network object framework designed to support a variety of high-performance applications. It is the basis for Ter'Angreal, a general-purpose browser application for entering and participating in 3D worlds.
The GTO format's primary usage is storage of static geometric data. The types of data you might find in a GTO file are things like polygonal meshes, various types of subdivision surfaces, NURBS or UBS surfaces, coordinate systems, hierarchies of objects, material bindings, and even images. It is used by film, video, and game production companies to streamline the modeling, animation, rendering, and 3-D paint processes. The distribution includes source code for a RenderMan Procedural plug-in, four Maya plug-ins, a Houdini plug-in, a number of command line tools, a Wavefront .obj parser, and two Python modules for reading, writing, and editing GTO files.