Blender is a free, open source program that was created for 3D animation projects, but is also extremely useful as 3d design software. It generally involves beginning with basic shapes (rather than sketches) and manipulating them into the preferred model, and includes a wide range of animation options.
There is also a second version of Blender called BforArtists, which greatly simplifies the interface and and makes it much easier to get started using the software.
Blender is open source software, anyone can download and install it for free on their personal computer.
BforArtists is open source software, anyone can download and install it for free on their personal computer.
Blender tutorials are available at http://www.blender.org/support/tutorials/.
BforArtists manual and tutorials are available at https://www.bforartists.de/wiki/bforartists-wiki