Now in its fourth year, the Z Film Festival slides toward irrelevance with this collection of mostly unpleasant and unenlightening videos that “explore the representation of sex and aggression.” Highlights include a bloodied nude with a whiskey bottle up her vagina (Meg McCarville’s Je Ne Regrette Rien), clips from Brian De Palma’s Carrie interspersed with gay porn (Charles Lum’s Indelible), and a bandaged mime squirting blood from her anus (Kristie and Usama Alshaibi’s Convulsion Expulsion). Only two selections have any humor or generosity: Marianna Beck, Joani Blank, and Jack Hafferkamp’s Orgasm! (17 min.), which cross fades among close-ups of 22 real people coming to climax, and Paul Lloyd Sargent’s White Blight Manifesto (6 min.), a goofy hip-hop video about gentrification in Humboldt Park. 84 min.