authors 
Brassel, Kurt E. and Fegeas, Robin 
year 
1979 
title 
An Algorithm for Shading of Regions on Vector Display Devices 
source 
SIGGRAPH '79 Conference Proceedings. August, 1979. vol. 13 ; no. 2: pp. 126 133 : ill. includes bibliography 
summary 
The display of shaded polygons by line, crosshatch, and dot patterns on vector devices is a task frequently used in computer graphics and computer cartography. In applications such as the production of shaded maps polygon shading turns out to be critical with respect to time requirements, and the development of efficient algorithms is of importance. Given an arbitrary polygon in the plane without selfcrossing edges (simplyconnected polygon), the task at hand is to shade this polygon with one or two sets of parallel lines where for each set a shading angle and a line distance are given. The basic concept of this new algorithm is to decompose the polygon into a set of mutually exclusive trapezoids (in special cases triangles) where the parallel edges of the trioxides are parallel to the desired shading lines. These trapezoids and triangles are then shaded in a fast procedure. In its present form the algorithm handles regions with up to 300 islands. Possible extensions include the construction of dash and cross patterns 
keywords 
algorithms, polygons, software, computer graphics, shading, GIS, mapping, drafting, information 
series 
CADline 
references 
Contenttype: text/plain

last changed 
2003/06/02 11:58 
