I wouldn't call GPU intimidating, more a royal pain in the butt! :) The approach of simply saving state doesn't work very well due to performance reasons. I.e.

I wouldn't call GPU intimidating, more a royal pain in the butt! :) The approach of simply saving state doesn't work very well due to performance reasons. I.e. If user is "editing" some of 5-10 million+ vertices, via some sort of brush tool that runs modifications to vertices through a GPU shader, then saving the state becomes a big no-no due to the huge delay in copying the entire current state of the vertices back to the CPU. This results in a short (but unusably irritating) pause, before the user can use the editing brush. Well just copy the bits you are interested in you may say, but there is no way I have came across to save only regions of the vertex buffer that the user "touches". There may be some fan-dangled way to save the "operations" not data, and then run them through a "reverse" shader, but I have a feeling that is overly complex and subject to inaccuracies. Darn, GPU's are fast though.