What it does
BRL-CAD is a free, open-source solid-modelling system with interactive geometry editing, ray tracing, geometric analysis and developer libraries. Its modelling kernel combines constructive solid geometry with boundary representations.
MGED stores a model in a geometry database. Start it, choose File > New, enter a filename ending in .g and confirm. File > Preferences > Units changes the working unit; calculations remain in millimetres internally. To add a sphere, choose Create > Ellipsoids > sph, name it and select Apply. The new object appears in edit mode with its position, orientation and size parameters visible.
The command window provides useful inspection controls: l followed by an object name lists its parameters, ls lists the database, and tops shows objects that are not members of another combination. Use erase to hide an object and draw to display it again. These display changes leave the stored geometry intact.
Deletion behaves differently. The kill command removes an object from the database, and the tutorial states that deletion has no undo. Changes are written immediately, without a separate Save command.
BRL-CAD supports Windows, Mac and Linux. The download page separates source archives, which require building, from platform-specific binary packages; those packages need not share the same release number.
Strengths
- Graphical and command controls can inspect the same geometry database.
- Solid geometry, rendering and geometric analysis belong to one system.
Watch out for
- MGED database deletions are immediate and cannot be restored with an undo command.
Best for
- Technical solid models built from geometric primitives
- Developers working with geometry and ray-tracing libraries
Sources
- BRL-CAD | Open Source Solid Modeling (Oct 28, 2026)
- BRL-CAD MGED Lesson | Creating Primitive Shapes (Oct 28, 2026)
- BRL-CAD | Downloads (Oct 28, 2026)