Using Inkscape and Blender:
http://www.youtube.com/watch?v=ows2QTiMRPg
https://docs.google.com/document/d/1GkL_MRxRb1Nu_Jr_6cWyeAMtX9hVuTI4VnDvWSJOGIw/edit
https://docs.google.com/document/d/1yQj-uivXutZ1Z-SCYMKNH7Hsuj6kqiXvKPj4O27onOs/edit#
Learn how to use Blender for 3D modeling:
https://www.youtube.com/user/cgboorman/videos?view=0
(start with tutorial 1, obviously)