BRL-CAD is a strong cross-platform constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing for rendering & geometric analyses, network distributed framebuffer support, image & signal-processing tools. The BRL-CAD package is a strong Constructive Solid Geometry (CSG) solid modeling system.

A particular strength of the package lies in its capability to build and analyze realistic models of complex objects using a relatively small set of "primitive shapes." To do this, the shapes are manipulated by employing the basic Boolean operations of union, subtraction, and intersection. Another strength of the package is the speed of its raytracer, which is one of the fastest in existence. Finally, BRL-CAD users can accurately model objects on scales ranging from the subatomic through the galactic and get "all the details, all the time."

The license of this software is Freeware, you can free download and free use this cad software.