I have a bunch of intersecting convex polygons, I want to find vertices of the outer contour of all those polygons. An individual polygon is not self-intersecting.

Could you please tell What could be a generic way of achieving this? Is there an API to do this?

PS: I'm developing a CAD drawing generator using .netdxf and C#.

Below is a simple example

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1 Answer 1


Sounds like you’re looking for a way to do a Boolean union operation. There’s a couple of algorithms linked from that article that should do the trick.

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    $\begingroup$ Please expand a bit on how to achieve the desired result. Link only answers are not encouraged here. If you link goes down or the page gets modified your answer becomes empty and irrelevant for any future visitors( here is a (admittedly fairly old) meta discussion on the topic : computergraphics.meta.stackexchange.com/questions/98 ) $\endgroup$ Commented Dec 7, 2017 at 20:00
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    $\begingroup$ @SebastiánMestre: This is not a link-only answer, as it gives the key term: Boolean union operation. If the link goes down, future visitors can look up Boolean unions in any computational geometry textbook. It would be a link-only answer if what it said was, "Check this link, the answer to your question is in there". $\endgroup$
    – user106
    Commented Dec 8, 2017 at 3:04

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