BRL-CAD... After 20 years of active development under a proprietary government license agreement, the BRL-CAD solid modeling suite has been released as Open Source software. BRL-CAD is one of the many legacies of the late Michael Muuss, author of ping. The package began on the PDP-11 and VAX 11/780--before the emergence of ANSI/ISO C language standards--and boasts one of the first parallel Ray tracers in existence. Today BRL-CAD has over 750,000 lines of source code. It incorporates both 3D modeling and rendering capabilities, and supports an API for user-developed geometric analysis applications. It continues to be developed and maintained by the U.S. Army Research Laboratory and its partners. Various portions of the package are distributed under the GPL, LGPL, GFDL, and BSD licenses.
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, network distributed framebuffer support, image and signal-processing tools.
Note: Now requires OS X 10.5 or later.