Responding to a set of parameters, what the artist calls “visual algorithms,” and following them to their conclusion, James Sienna creates drawings, prints, and paintings that combine mathematical precision with hand-drawn variation. Siena’s works, characterized by repetition and dense with lines, range from the purely abstract to the vaguely biomorphic to the figurative. Known primarily for his concentric or repeating contours and corners, a 2008 exhibition marked a departure, featuring greater irregularity of line and a number of drawings of human faces.