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Asked: 2026-05-13T23:14:04+00:00

I have been searching everywhere but I could not find an answer. I need

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I have been searching everywhere but I could not find an answer. I
need to have drawing resizable polygons with mouse interaction but I
do not want irregular, overlapping or intersecting polygons in the
end.

Here is a simple example of drawing resizable polygons
http://www.wolfpil.de/polygon.html

You can easily create & resize polygons which is great. But I need an
extra functionality to detect intersections and NOT allowing weird
looking shapes/polygons.
You can see the problem in this video:
http://www.youtube.com/watch?v=zou2jcGM8zw

The only solution for that problem I found at http://www.wikimapia.org. They have added features to handle the problem.
You can see it in this video: http://www.youtube.com/watch?v=K7-K0k2D-2A

I spent 3 days trying out to achieve something like this. I have gone
through wikimapia’s javascript code but it is way too complex for me
to understand.

In sum, it does not have to look as fancy as as wikimapia’s. I just
need resizable polygons which do NOT intersect while resizing or
adding new points to it. Can you give me any suggestions how to
achieve that?

Thank in advance.

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1 Answer

  1. Editorial Team

    Depending on how many points that you allow, a naive, simple O(N^2) line intersection algorithm suffices. Algorithmically this is not the best solution, but for starting out it’s the most accessible for a beginner in computational geometry.

    For starter, see Wikipedia article on line segment intersection. One of its links has an easy to understand explanation on how to compute the intersection point of two line segments.

    Good luck!

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