BRL-CAD: An Open Source CSG solid modeling system with ray tracing support for rendering and geometric analysis, network distributed framebuffer support, image-processing and signal-processing tools.
J&L Associates: Developers of the ActiveSolid 3D solid modeling, CAD prototyping and mark-up sharware application and the underlying BspSolid modelling library.
MINOS: A free 3D solid modelling software offering fast hidden line removal, topological functions, 3D geometric constructions, IGES support, shading, printing, hatches, and line constructions.
RogCAD: Keyboard driven modelling software that supports complex curved surfaces.
solidThinking: Modelling software that supports NURBS, polygonal modeling, and subdivision surfaces, available for Windows and Macintosh.
TouchCAD: 3D modeling, unfolding and unwrapping program for Macintosh and Windows.
