Re: polygon buffering algorithms

If you have a set of lines that represents a closed polygon, the following pseudo-code should work

foreach edge (edges in polygon, clockwise)
   construct parallel line distance d from edge, store it in an array
done
foreach parallel line
   find intersection with next line in array, allowing for wrap around
   store intersection in an array
done
#intersections are the vertexes of your new polygon
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If you need more, let us know.

thor

Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come

Comment on Re: polygon buffering algorithms Download Code

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Re^2: polygon buffering algorithms by ikegami (Patriarch) on Feb 08, 2005 at 18:17 UTC
................................... ................................... ................................... ................................... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... ...............!!!!!!!!!!!!!!!..... ...............!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... .....!!!!!!!!!!!!!!!!!!!!!!!!!..... ................................... ................................... ................................... ................................... [download] The above with $d == 3 gives a weird polygon, but that's ok as long you're expecting it. Read more... (854 Bytes)	[reply] [d/l] [select]
Re^3: polygon buffering algorithms by thor (Priest) on Feb 08, 2005 at 19:13 UTC
You're right...the algorithm that I outlined works for convex polygons. In order to deal with polygons with concavities, I believe that you need to allow for overlap and take the union of all points that lie in the interior. In the case of the polygon that you gave, it would then be a square. Just for my own edification, what is the $d that you're referring to? thor `Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come`	[reply]
Re^4: polygon buffering algorithms by ikegami (Patriarch) on Feb 08, 2005 at 19:53 UTC
The OP refered to "buffer distance 'd'". That's what I meant by `$d`. (I added the `$` without thinking.)	[reply] [d/l] [select]