Chinese film stars Tony Leung and WEI TANG spent two weeks filming sex scenes for LUST, CAUTION - because director Ang Lee found the experience "exhausting." Lee admits he was forced to halt filming several times as shooting the steamy scenes was too challenging. He explains, "If we were shooting a porno film, we would have done all those scenes in two days. "After half a day, I'd have to call a stop because it's so exhausting. Physically it's not that difficult, but it's mentally exhausting."