Good question,
well I guess easiest way would be to use one of screen recording SWs and record the gameplay at a high frame rate.
You can also take screenshots using F9 or console commands:
Maybe would be possible to try adding this screenshot Console Command to Tick function,
so it would make a screenshot every tick, but as far as I know Console Commands can take several ticks to execute so we’d have to find related screenshot function in the source code and use that.
But it’s still much easier to use some screen recording software :D.