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.
Teddy is an OpenGL-based 3D graphics library written in C++. Its main features are simple scene graph and windowing system-enabling multiple cameras, camera windows, and scenes. It focuses on easy and flexible manipulation of models and model materials in the scene graph. It contains a number of primitive objects like sphere, box, and cone, and it can load LightWave object and scene files.
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.
Moonlight|3D is a modeling and animation tool for three-dimensional art. It currently supports mesh-based modeling. It's a redesign of Moonlight Atelier, formed after Moonlight Atelier/Creator died in 1999/2000. Rendering is done through pluggable backends. It currently supports Sunflow, with support for RenderMan and others in planning.
FreeCAD is a CAx RAD based on OpenCASCADE, Qt4, and Python. It features some key concepts like Macro recording, Workbenches, and the ability to run as a server. It's also platform-independent. It is is fully scriptable and designed to be easily extensible; only the core functionality is embedded into the core libraries, but all further functionality like support of triangle meshes, CAM, FEM, etc. is implemented in extension modules. Normally, such a module is divided into an 'App' part containing the data structures and algorithms and a 'GUI' containing the graphical representation of data structures, dialogs, workbenches, etc.