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Real Time Fitting of Hand‐Sketched Pressure Brushstrokes
Author(s) -
Pudet Thierry
Publication year - 1994
Publication title -
computer graphics forum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 120
eISSN - 1467-8659
pISSN - 0167-7055
DOI - 10.1111/1467-8659.1330205
Subject(s) - stylus , trajectory , piecewise , computer science , bézier curve , algorithm , computation , computer graphics (images) , mathematics , computer vision , geometry , mathematical analysis , physics , astronomy
A method is described for fitting the outline of hand‐sketched pressure brushstrokes with Bézier curves. It combines the brush‐trajectory model, in which a stroke is generated by dragging a brush along a given trajectory, with a fast curve fitting algorithm. The method has been implemented for a vector‐based drawing program in which the user draws with a cordless pressure‐sensitive stylus on a digitizing tablet. From the trajectory followed by the stylus, its associated pressure data, and a specified brush, a stroke of variable width is computed and displayed in real time. First, the digitized trajectory is fitted, thus removing noise. Then, from polygonal approximations of the fitted trajectory and the brush outline, a polygonal approximation of the stroke outline is computed. Working with polygonal approximations reduces computations to simple geometric operations and greatly simplifies the treatment of dynamic, pressure‐controlled brushes. Last, the polygonal approximation of the stroke outline is fitted. The result is a closed piecewise Bézier curve approximating the brushstroke outline to within an arbitrary error tolerance. Several examples of hand‐sketched drawings realized with this method are presented.