#868 Generalization of PNG Walk Tool?

[Jeremy Faden]

Connor has an animation where he wants slices of data, put together into an animation. This could be parameterized, and to calculate each frame you have to do lots of work. The PNG Walk saves the work from image to image, but it only works on times. (Also it is not parallelizable, yet.) If a facility for creating each frame given a previous state, so each script invocation would just apply the "deltas" to get to the next frame, the PNG Walk Tool could be reimplemented with this, and it could be made parallelizable by running N worker threads, each keeping its state.