BRL-CAD is a powerful Combinatorial/Constructive Solid Geometry (CSG)
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, and an embedded scripting language.

The package is a collection of over 400 tools and utilities across
over 750,000 lines of source code.  Included is support for various
geometric data format conversions, image and signal processing
capabilities, sophisticated ray-tracing based lighting models, network
distributed ray-tracing, massively parallel ray-tracing, animation
capabilities, data compression, image handling, and interactive 3-D
geometric editing.  Included is an implementation of Weiler's
n-Manifold Geometry (NMG) data structures for surface-based solid
models and photon mapping.