I'd just like to add a link to the excellent Helix 3D Toolkit , which is a collection of controls and helper classes for WPF 3D. It is an active project that includes improved versions of everything from 3D Tools and a lot more. It is published under the Ms-Pl license, which is a bit more liberal that the 3D Tools license.

I have been using the Helix 3D Viewport for nearly two years, and it works very well. This 3D Tools project was an interesting start, but has not been active for many years, and finding Helix toolkit made it easy to stick with WPF 3D.

So, definitely worth a look if you are interested in WPF 3D at all.