Some attempts at producing a hatching style effect using UberNoise.osl (cell) -> toon.mask_color. In some cases the effect works better when Camera (AA) samples are low (3) as it tends to break up the edges around the highlights and creates more of a sketch style.

docs.arnoldrenderer.com/display/A5AFMUG/Toon… https://docs.arnoldrenderer.com/display/A5AFMUG/OSL