You can do that already, actually! Simply open up Matinee and click the tool bar button called “Movie”. It will bring up an window that lets you set options for capturing your game to video. If you want to record yourself playing the game (and not just a Matinee cutscene), remember to turn off the “Enable Cinematic Mode” option. Also, I’d suggest enabling the “Close editor when capture starts” button so that you can smooth performance. While in the game, you can type “StopMovieCapture” and “StartMovieCapture” to do retakes.
On a related note, if you want to record a perfectly-smooth high resolution cinematic animation you can use the “-DumpMovie” command-line argument. This will turn off audio (you need to mix it in later), but will go frame by frame and dump out a video that will look great when played back in HD. This is how we spit out videos of our cinematics.
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