Rewind

[alex-moon]

It's not uncommon for a long-running render to go bad late in the game, e.g. after running for 24 hours or longer. In this case, instead of restarting from scratch, we'd like to "undo" a certain number of steps. There's quite a lot involved in this:

1. You need to set steps_completed to the appropriate number.
2. You need to delete all generated output frames from the steps folder.
3. You need to copy the most recent output frame to output.png.
4. You need to scale output.png back down to the expected size.

All of this is extremely prone to human error, so having a button I can hit to get the computer to do it for me would be super handy.