A new academic paper, “Deep Normal Estimation for Automatic Shading of Hand-Drawn Characters” (Jan 2019)…
“We present a new fully automatic pipeline for generating shading effects on hand-drawn characters. Our method takes as input a single digitized sketch of any resolution and outputs a dense normal map estimation suitable for rendering without requiring any human input.”
Currently an ugly and unconvincing effect, which in the examples gives a heavy raised-relief shading. It reminds me of a child’s slightly-padded plastic puffa-sticker…
… but it’s interesting that such shading can be done at all in an automated manner, from basic 2D line-art without any reference to either the coloured version or a 3D model.