mjbWorld is a standards based 3D editor, which can graphically edit and allow users to see and interact with X3D (VRML) and other 3D formats. It is also intended to provide a platform which can be used to experiment with physics, animation, etc. Versions for Java, C++ and C# are included.
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.
pythonOCC is a 3D CAD/PLM development library for the Python programming language. It provides 3D hybrid modeling, data exchange (support for the STEP/IGES file format), GUI management support (wxPython, PyQt, python-xlib), parametric modeling, and advanced meshing features. pythonOCC is built upon the OpenCASCADE 3D modeling kernel and the salomegeom and salomesmesh packages. Some high level packages (for parametric modeling, topology, data exchange, webservices, etc.) extend the builtin features of those libraries to enable highly dynamic and modular programming of any CAD application.
The GNU Triangulated Surface Library (GTS) provides a set of useful functions to deal with 3D surfaces meshed with interconnected triangles. It features metric operations (area, volume, curvature, etc.), 2D Delaunay and constrained Delaunay triangulations, robust geometric predicates and set operations on surfaces (union, intersection, etc.), surface refinement and coarsening (multiresolution models), and bounding-boxes trees for collision/intersection detection.
Sauerbraten (a.k.a. Cube 2) is a free multiplayer/single player first person shooter, built as a major redesign of the Cube FPS. Much like the original Cube, the aim of this game is not necessarily to produce the most features and eye candy possible, but rather to allow map/geometry editing to be done dynamically in-game, to create fun gameplay and an elegant engine.
WilmaScope is a Java3D application that creates real-time 3D animations of dynamic graph (network) structures. It comes with a number of layout algorithm plugins, and supports the easy creation of plugins for new layout algorithms. 3D geometries for graph element glyphs and algorithms for graph generation and modification are loaded dynamically as plugins, providing an extremely flexible platform for all manner of graph visualisation applications. The system has been applied with considerable success to a number of graph visualisation problems.
SDXF (Stani's DXF) library can generate complex CAD drawings in the DXF format with all kinds of entities, such as 3DFace, Arc, Insert, Circle, Line, Mtext, Point, Polyline, Rectangle (optionally filled), Solid, and Text. They can be structured with Layers, Blocks, Linetypes, Text styles, and Views.