No surprise, I haven’t been on the bus for Ben Stiller’s Tropic Thunder, his spoof (due Aug. 15) about Hollywood narcissists making an expensive Vietnam War epic who find themselves embroiled in a real armed conflict. But Rain of Madness — now, that looks funny to me. It’s the side project, the mockumentary making-of film about the movie shoot chronicled in Tropic Thunder, the Hearts of Darkness to its Apocalypse Now. (Note the Doors-y music cues on the Rain of Madness trailer.) Rain has its own official website, and you can download the trailer for free at iTunes. (Warning: it contains some NSFW language and more of Steve Coogan’s bum than you may want to see.) Watch Coogan (pictured), Stiller, Robert Downey Jr., and Jack Black in the Rain trailer, and tell me if you don’t think Rain looks funnier than Tropic Thunder itself.