The WPF/E Gear Keeps Turning
First the SDK team created an article about generating reflections in WPF/E. Then today I read [via Mike Harsh] about Michael Schwarz extending the example to include an animation. I also read in Mike's post about the WPF/E google group (joined!) and in the group I read Dave Campbell's post about extending the example further to roll the gear across the screen. I couldn't help myself and I took it one step further and gave the rolling motion a little twist so that it looks like the wheel accelerates and hits a wall.
This is done using a SplineDoubleKeyFrame, which allows you change how the keyframe is interpreted. I had no idea how this worked until I came across this post by Karsten where he demonstrates creating bouncing balls in WPF. I borrowed his SplineDoubleKeyFrame but when I applied it to the gear it started fast and then went slow and I wanted it to do the opposite. I didn't understand how the SplineKey worked but came across another post by Karsten where he gives you the code for the Bezier Time which is a WPF app that he wrote to better under stand the effects of the SplineKey. Unfortunately the app was written with one of the beta versions and no longer worked, but I was able to get it running after some rework (although one of the animations is broken still). Using that tool I was able to figure out how to invert the curve and get the effect that I wanted.
The SplineDoubleKeyFrame is definately the way to get the dog ears effect going, now I need to go read up on beziers and splines. :)
Download Gear.xaml