Machinima (/məˈʃiːnɨmə/ or /məˈʃɪnɨmə/) is the use of real-time computer graphics engines to create a cinematic production. Most often video games are used to generate the computer animation. Machinima-based artists, sometimes called machinimists or machinimators, are often fan laborers, by virtue of their re-use of copyrighted materials...
I first found out about this in the Simming community where there are thousands of blogs devoted to various players Sims stories. Most of these blogs are on tumblr and Live Journal. there seems to be an entire section of Live Journal devoted to Simmers, actually. Sometimes they will have competitions/challenges just for the hell of it. Its kind of an interesting subculture.