Center of a polygon
BlitzMax Forums/BlitzMax Programming/Center of a polygon
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| How to calculate the center of a polygon? Got polygon data as array like DrawPoly parameter needs. |
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| Regular Polygons would be easy...irregular ones.. Try something like creating a hull. Or something like: search to points with the largest distance, the center of that line is the point where a circle would cover all polygon points. But in general: irregular polygons don't have a center. At http://mayastation.typepad.com/maya-station/2009/11/where-is-the-center-of-a-polygon.html Someone suggests to use weighted points to get an average center. So to conclude: you won't be able to do it in a feasonable time so look for a method to do it "quick and dirty". bye Ron |
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| Guess I will do the hull thing, calculate a rectangle from the maximum coordinates. That would do it. |
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| If you wanted an accurate centre of gravity my experiments with the glu tesselator would be useful (http://www.blitzbasic.com/Community/posts.php?topic=97548) Step 1: Tesselate the polygon Step 2: Find the average point of each triangle Step 3: Average the averages The glu functions are not reliant on OpenGL so it doesn't matter what graphics driver you're using. Plus it's really fast. In reality you'll probably find that averaging all points will be good enough. |
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| Instead of an rectangle hull I think a circular one would fit better... The longest Distance between two points contains at its middle the center of the circle... the half of this distance would be the radius. so you have to do some calcs ... Point A to Rest, Point B to Rest but A, Point C to Rest but A,B ... There are surely some better procedures but thats the simplest one. bye Ron |
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