FreeSG ("Free" as in "Free of bloat") is a portable, high-level open-source 3D engine with an emphasis on generality. It is built on top of the Agar object system and GUI. FreeSG is available under a revised BSD license. The project is currently in very active development.

Unlike most typical 3D engines, FreeSG is designed as an integrable component, as opposed to an application framework. It includes libraries for 3D scene graphs (SG), vector drawings (SK), computational geometry and math routines (M).

With the SG library, we aim to implement a set of efficient scene rendering algorithms where the speed and memory tradeoffs can be adjusted to the widest possible range of professional applications and hardware platforms. We use a generic, extensible scene description language with a compact binary file format. Our objects use an unambiguous polyhedral representation based on the halfedge structure, which allows for fast geometric queries.

The SK library provides precisely dimensioned 2D vector drawings (or sketches), and supports geometrical constraint systems using a graph-directed algebraic method. This is an important component to one of our major FreeSG-based projects, cadtools.

The M library is a general math and linear algebra package. It features basic linear algebra routines (including optimized versions for 2/3/4 dimensional vectors and 4x4 matrices), complex-number arithmetic, quaternions and computational geometry routines such as intersections.

The FreeSG project is sponsored by Csoft.net: Security conscious, high-availability Unix hosting on redundant server arrays.

"The idea is if you use those two shapes and try to colour the plane with them so the colours match, then the only way you can do this is to produce a pattern which never repeats itself." -- Roger Penrose