Geometry: The dynamic version of the drawing algorithms as described in [19] generates whirl strokes. This results from whirls in the vector field. A bigger smoothing kernel for the vector field suppresses most of these artifact, but does not remove all of them. A fast approach to reduce the whirls is to compute the ratio of the bounding rectangle R of a stroke sc and compare it to its current length l(sc). The whirls and the improved results can be seen in Fig. 3.