FREE ABSTRACT (to read the full article, please log in below).
This paper presents an efficient line-offset algorithm for general
polygonal shapes with islands. A developed sweep-line algorithm (SL) is
introduced to find all self-intersection points accurately and quickly.
The previous work is limited to handle polygons that having no line-segments
in parallel to sweep-line directions. The developed sweep-line algorithm
(SL) saving the calculation time and using a new method to find polygon
self-intersection points. An invalid loop detection and removing (ILDR)
algorithm is developed. The invalid loops detection algorithm divides the
polygon at self-intersection points into a set of small polygons, and re-polygonized
them. The polygons are checked for direction; invalid polygons are always
having inverse direction with the boundary polygon. The proposed algorithm
has been implemented in Visual C++ and applied to offset point sequence
curves, which contain several islands
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© Copyright 2002 Professor F.R. Hall - University of Wolverhampton.