A cross-hatching / pencil simulation built in C++ with openFrameworks. Based on Microsoft Research's paper, "Real-Time Hatching." Uses a variety of shader passes to simulate gestural, layered strokes on 3D objects instead of traditional Phong shading.
Lighting calculations determine a series of "weights," which are subsequently used to blend between an array of pre-composed textures. These textures are formally known as a "tonal art map."