This is brilliant thanks! My update function needs to update positions and velocities from previous frames. Should i do another cache for velocities? I've been converting the mesh data to and from numpy arrays. should I do the conversion in the update function or store the cache as a numpy matrix and convert back in the frame handling function? thanks again this is just the help I needed.

Thanks! That's interesting. It works really well for this simple example I asked for but I actually intended to do a physics sim. Calculating backwards seems excessive. Blender turns the timeline blue and caches past frames. Is this functionality in the python api? many thanks again really helpful answer.

My goal is to write my own physics simulation, like the one blender has and I would like to interact with it in the same way. I would like to be able to hit play and the simulation caches the frames it processes and i can scroll back and forward through them, just like blender's physics sim

unfortunately this gives an error Keyerror

ok, i think I understand. thanks again!

thanks! Why are you using a dictionary?