Every UIelement has a Property named clip, which is Geometry type. You can set any geometry used to define the outline of the contents of an element. Only the area that is within the region of the geometry will be visible. Portion of UIelement outside the geometry will be visually clipped in the rendered layout. Using Clip property of UIelement in WPF, you can do lots of animation. I think it is a powerful way of doing animation. Possibilities are endless. You can do most geometrical type of animation in 2D using this technique. I have just published an article about this technique.
Here it is:
http://www.codeproject.com/KB/WPF/ClipBasedAnimationWPF.aspx
An animation consists of a series of frames. To perform the animation, these frames are shown one after the other at a regular time interval. I have just published an article about how i came up with marquee text control, Drip animation, and Roll animation.
Here it is:
http://www.codeproject.com/KB/WPF/WPFAnimation1.aspx