Cake is powerful 3D game engine and (as a reference application) map viewer
for id Software's Quake III Arena maps.  It currently features:

    * BSP (+PVS) support
    * collisions detection (with normal faces + patches)
    * shaders + textures
    * lightmaps
    * vertex deformations
    * cloudbox + skybox (nearbox and farbox)
    * volumetric fog
    * bezier surfaces (with variable LOD)
    * multiple viewports
    * console
    * record/playback demo support (DM3 format not supported)
    * background music + 3D sounds (not under FreeBSD though)
    * models
    * entities (with variable LOD)
    * zip compressed files (*.pk3)

WWW: http://www.calodox.scene.org/morbac/cake/