A promising new 2020 paper, “Generating Digital Painting Lighting Effects via RGB-space Geometry”. Along with the paper are Python scripts that inspect your digital painting, detect where “the density of strokes” are, and then intelligently re-light the painting accordingly.
It’s ‘early days’ for this and similar experimental re-lighting techniques. But one wonders if it could be used on 3D renders, perhaps if they were output along with a quickly-calculated data-file that served as a proxy for “density of strokes”. That would perhaps be the equivalent of Poser’s Sketch rendering, but without the rendering — only the stroke density data would be saved, as a text file. Poser can already save its stroke data for export to Corel Painter.