If you didn't shell out 50 bucks for yesterday's official opening film and party, your SIFF should begin with this terrific experimental documentary, a "remix" of Michael Glawogger's controversial 1998 film Megacities, about members of the urban underclass. The sampled footage (including some new outtakes) becomes electric in this pulsating, rhythmic edit: A dye-sifter in Mumbai turns purple and green after a day spent crouching over his powders, a junkie in New York demonstrates his various hustles, and a young man in Tokyo seems in danger of going hikikomori, given his inordinate affection for huggable girl-shaped pillows. (Northwest Film Forum, 1515 12th Ave, 324-9996. 9:15 pm, $10.)