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.
Shapeways - Ships physical realizations in a variety of materials of uploaded models. Includes available materials, formats accepted, pricing, tutorials, and support.
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.
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