"Sketching" is a drawing process that displays
successive approximation: the scene is first coarsely rendered,
then successively more precise strokes are overlaid to improve the
rendition. Edges and contours are segmented into a number of
(often overlapping) strokes, with shorter strokes characteristically
chosen in high-curvature regions.
In this paper we approximate the feel and strategy of such contour stroking.
Simple curvature-based segmentation schemes (such as breaking contours at
curvature maxima) will not always work for this purpose,
both because the initial contour
description may contain high curvature artifacts from rasterization and
noise, but more importantly because sketching initially ignores small
details regardless of whether they correspond to high-curvature locations
on a contour.
We approach this problem with a perceptual segmentation scheme
that combines an affinity measure incorporating perceptual continuation
with recent segmentation algorithms.
The resulting algorithm produces strokes that strongly resemble
those chosen by trained artists. In addtion, it has a scale
parameter than can be scheduled to produce the coarse-to-fine
successive approximation seen in sketching.
Graphite 2005 paper:
More Optimal Strokes for NPR Sketching
(Left) breaking silhouettes at curvature maxima works poorly if there are small details, noise, or rasterization artifacts
on the contour. (Right) Strokes obtained using perceptually
oriented segmentation break at more salient points.