animating the angle of an arc in SVG

Take a look at http://cs.sru.edu/~ddailey/svg/clipArc4.svg 

 

I was trying to redo Erik Dalhstrom's very lovely example at
http://xn--dahlstrm-t4a.net/svg/clippath/animated-clippath-arc.svg by using
only declarative techniques. (Animated SVG can be shown at Ello while
scripted animation can't be - another good reason for Microsoft to support
SMIL! Since then a new audience can see what it can do without having to
already be an SVG enthusiast!)

 

Originally I used eight points of the circle as endpoints of the animation,
holding the radius constant, but needing to swap the arc flags at 180
degrees. Twelve looked better than eight, but it is still quite jerky.

 

Any ideas on how to improve it? 

 

Experimenting with other parts of the path/arc subcommand syntax may be seen
at 

http://cs.sru.edu/~ddailey/svg/arcAngle.svg

 

cheers

David