In the past year quite a bit of work has been done on the 3D code and there are 2 main 3D branches. The one has a small set of 3D code intended for merging with the main branch in the short term. This branch introduces model caching, a plugin system for handling new types of 3D models, a new scheme for locating 3D models (which will hopefully be easy to use), and a new 3D file browser with preview. This is the branch which requires the most testing since we hope to include it in the main branch soon:
bzr checkout lp:~cirilo-bernardo/kicad/3d_initial_merge
The other branch which is maintained by Mario Luzeiro implements the new 3D Viewer; this branch makes use of the cache system and 3D plugins of the branch mentioned above:
bzr checkout lp:~mrluzeiro/kicad/kicad_new3d-viewer