Power 3D design app
3 D modelling apps are never easy to master for the uninitiated and this is no exception. However, if you do spend a bit of time feeling your way round, you'll soon be making the 3D animations that you never dreamed possible. The best thing about this program too is that unlike many 3D modelling apps, it's completely free and licensed under GNU.
Despite it's complexity, there are fortunately a ton of tutorials to help you get to grips with it. There's no danger of making to many mistakes because you're armed with an unlimited number of undos and redos. Whilst playing back your creations, you can also interact and "sculpt" them at the same time to help you mould the movements into exactly what you want.
According to the developers, what makes this such a powerful application is that it uses the Pixar Renderman Interface to render motion-picture-quality images with a wide variety of rendering engines. In this way, it test all the possible rendering possibilities to produce the best final results in your creations. You may find however that certain textures and constructs do not render properly due to the fact that this is still a GNU project and in constant development.
Be under no illusions that this is a complicated package to learn but considering it's free and that it renders 3D images so well, it's worth the effort.