Well, there are both types of cutscenes. some are rendered, some are rendered in real-time inside the game. lol I know how to write those ingame-cutscenes, but can't think of the possibility to watch them outside.
edit: the ingame-rendered cutscenes are produced by ICARUS script files (to be found in the base\scripts directory) and the pre-rendered cutscenes are .roq files. there is a manual how to make those roq-files in the JK2-editing package, but none how to view them

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