Question about saving replays

Hello to everybody. I’m here to ask some advise. In my project I want to save a little video( a replay) from the game. The user will press a button from the GUI and the game will record what he does in a video file. Later he will be able to see it loading it in a videotexture.

I need to record a SoftBody simulation so I’m looking for a strategy which may not compromise the FPS and of course it cannot be done saving a file with the users actions. I’ve read about a technique which consist in taking images at every frame using Rasterizer and then compile them in a video using an external program but I need to know if there is another way to do this or any other advise that you could give. Thanks a lot for your time.