Crystal Space is a free (LGPL) and portable 3D Game Development Kit written in C++. It supports: true six degrees of freedom, colored lighting, mipmapping, portals, mirrors, alpha transparency, reflective surfaces, 3D sprites (frame basedor with skeletal animation), procedural textures, particle systems,halos, volumetric fog, scripting (using Python or other languages), 16-bit and 32-bit display support, OpenGL, and software renderer, font support, hierarchical transformations, ... See the extensive list of features for more details.
Crystal Space currently runs on GNU/Linux, general Unix, Windows, Windows NT, and MacOS/X. It can optionally use OpenGL (on all platforms), Allegro (GNU/Linux), X11 (Unix or GNU/Linux) and SVGALIB (GNU/Linux). It can also optionally use assembler routines using NASM and MMX.
Crystal Space is a large open source project. There are about 670 people subscribed to the Crystal Space mailing list (see the Contact Page for more information about how to subscribe).and this list is very active (2718 messages in the first eight months meaningabout 11 messages a day on average, Note that in the last three months there havebeen about 50 messages a day! YOU HAVE BEEN WARNED!).