After doodling a few black holes, I tried my hand at other weird surfaces, starting with this #cusp. Although a cusp appears to be a sharp spike in 2D, it is the result of a smooth surface in 3D. Learn more about the cusp and #CatastropheTheory in Allan McRobie’s beautiful book “The Seduction of Curves.” This piece is 3” square, ink and colored pencil on paper. #math #geometry #MathArt #ColoredPencil #catastrphe #doodle