Binary Shading Using Appearance and Geometry

In the style of binary shading, shape and illumination are depicted using two colors, typically black and white, that form coherent lines and regions in the image. We formulate the problem of assigning colors in the rendered image as an energy minimization, computed using graph cut on the image grid. The terms of this energy come from two sources: appearance (shading) and geometry (depth and curvature). Our contributions are in the use of geometric information in determining colors, and how this information is incorporated into a graph cut approach. This optimization yields boundaries between black and white regions that tend towards being shorter and to run along geometric features like creases. We show a range of results, and demonstrate that this approach produces more coherent images than simpler approaches that make local decisions when assigning colors, or that do not use geometry.