The generous spirit of a generation too often disparaged is on full view in writer/director Greg Harrison’s stylish and fun Groove, the story of one night in San Francisco’s underground rave scene. There’s Ernie (Steve Van Wormer), embodying typical GenX entrepreneurial gung-ho in risking arrest by organizing, with almost frightening efficiency and for no pay, the big party in an abandoned warehouse merely for the gratitude he gets from ravers. There’s Leyla (Lola Glaudini), who takes advantage of Xer friendliness by scoping out a ride to the rave from total strangers via an Internet newsgroup. There’s David (the terrific Hamish Linklater), a technology writer and recent transplant from the Midwest who’ll find refuge from Xer geekiness at the rave his brother, Colin (Denny Kirkwood), drags him to. There’s no bar at Ernie’s rave, but there is plenty of fruit and bottled water to counter Ecstasy- and dancing-induced dehydration — and there’s also lots of non-judgmental sexual experimentation. Harrison celebrates the freedom and joy of ravers — watch for the girl, early on in the film, who’s got music so in her blood that she bops to the rhythm of dryers in a laundromat — but he doesn’t ignore the ultimate futility of a life that consists of nothing but partying, exploring fears of real intimacy that dog some of his ravers. (I doubt Harrison intends it as mere happenstance that the gay couple who plan to commemorate the anniversary of their meeting at another rave never manage to make it to this one.) Still, Groove is mostly infectious and exciting, and made me wanna get up and dance in the aisles.