Extracting frames from a WPF storyboard

I would like to generate a set of still-frames from an animated WPF storyboard. My goal is to be able to specify a frame-rate, and 'record' any WPF Storyboard, which will generate still PNG images of each 'step' in the timeline. Then I can wire them together any way I like (animated GIF, AVI etc etc). Can anyone with indepth exper开发者_开发技巧ience with WPF animation tell me what is the best and most abstract way to go about this?

An important point to stress is that the 'capture' of the animation be as non-invasive to the animation's performance as possible.

Thanks!