“Drawing and animation using skeletal strokes” by Hsu and Lee

The use of skeletal strokes is a new vector graphics realization of the brush and stroke metaphor using arbitrary pictures as “ink”. It is based on an idealized 2D deformation model defined by an arbitrary path. Its expressiveness as a general brush stroke replacement and efficiency for interactive use make it suitable as a basic drawing primitive in drawing programs as well as windowing and page description systems. This paper presents our drawing and animation system, “Skeletal Draw”, based on skeletal strokes. The effectiveness of the system in stylish picture creation is illustrated with various pictures made with it. Decisions made in the handling of sub-strokes in a higher order stroke and recursive strokes are discussed. The general anchoring mechanism in the skeletal stroke framework allows any arbitrary picture deformation to be abstracted into a single stroke. Its extension to piecewise continuous anchoring and the anchoring of shear angle and stroke width are explained. We demonstrated how this mechanism allows us to build up powerful pseudo-3D models which are particularly useful in the production of 2 1/2 D cartoon drawings and animation. Animation sequences have been made to illustrate the ideas, including a vector graphics based motion blurring technique.

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