BRL-CAD
BRL-CAD is a powerful cross-platform open source solid modeling system with interactive geometry editing, high-performance ray-tracing for rendering and geometric analysis, a system performance analysis benchmark suite, geometry libraries for application developers, and over 30 years of active development.
BRL-CAD values your independence, thus our code is open source under OSI-approved licensing terms, allowing you to tailor it to your own needs. It also means that you will receive this software free of charge, with no additional charges for updates or support.