Wayne Thiebaud is rightfully celebrated for his colorful Pop Art-ish paintings, like the one from 1963 of three gumball machines prominently displayed at the de Young. Thiebaud has talked about the playfulness he puts into his work, but the iconic artist has a shadow side that's showcased at his son's North Beach art space. Drawings of nudes — people who are dour, agitated, pensive, contemplative, or otherwise uneasy — fill the upper floor at this gallery. Many of the people depicted look as if they didn't want to be drawn. A couple on a bed acts as distant from each other as possible given the proximity of their flesh. These paintings have one thing in common with the Wayne Thiebaud charcoal drawings that hang in the gallery's first floor: They're stripped of any pageantry. We get the bare essence of the drawn figures and objects. This doesn't mean that the cups, saucers, toys, and nudes are all downers. If you're in the mood for starkness and realism, these offerings are just the thing to see.