Animate the points on a path or clipping path
In Microsoft Expression Blend 2, you can now animate the points (or vertices) on a path object. For example, you could animate the points of a clipping path to gradually reveal the object underneath the clipping path. You could convert text in a TextBlock to path objects, and then animate the letters to change them into other shapes, perhaps even reversing the storyboard so that you start with shapes that change into letters.
Path objects are created by the Pen tool, the Pencil tool, and by converting other objects (such as shapes or text) to paths.
To animate the points on a path or clipping path
If you do not have a path object on the artboard, you can create one using one of the following options:
Under Objects and Timeline, select the path object that you want to animate.
In the Toolbox, select the Direct Selection tool. The points of your path object are identified on the artboard by small squares.
Move the timeline playhead to the location on the timeline where you want to record a change in one of the points.
On the artboard, use your mouse to drag, or ALT+drag, individual points and line segments to new locations. You can also select the Pen tool to add or remove points on the path.
If you add or remove points when in timeline-recording mode, the results take effect from the start of the timeline. For example, removing a point changes the starting shape of the path as if you had removed the point when not in timeline-recording mode.
For a list of the different ways that you can modify a path, see Pen and direct selection usage.
Continue moving the timeline playhead and modifying points until you complete your animation.