# How to reduce polygons and prevent intersection

I'm working on a piece of software that deals with several polygons, These polygons have far to many corners and I would like to reduce them such that the total area in the polygons and general shape don't change overly much (within a few percent). There is however one problem and that is that these polygons are not allowed to intersect.

These polygons can also be inside of each other or next to each other. So for example the following polygon

should not be simplified into

Because now we have an intersection

but something like

is ok. Do note how it's possible for one polygon to contain another.

This is also something I would (if possible) like to be somewhat efficient with, currently the program is bottlenecked by an O(n^3) calculation somewhat later so any solution that is faster then that is good but anything O(n³) or slower is a no go. Anybody know how to check this efficiently?

• I hope I picked the right stack exchange for this, I also considered the computer science exchange. If this is OT here please don't be mad. Mar 15, 2017 at 21:17
• You should consider Stack Overflow. Mar 15, 2017 at 21:25
• It looks for me like collision detection with bounding areas that detects intersection between circles or polygons, particularly if the distance between the circles' centers is less than the circles' combined radii (length < || > r1 +r2). For more complicated scenarios, such as collisions between polygons of arbitrary size and shape you could use the Separating Axis Theorem - a mathematical equivalent of shining a light on two polygons from different angles.
– LAAE
Mar 16, 2017 at 1:15

You might start by computing the Hausdorff distance between the two polygons. It can easily be done in $O(n^2)$ time where $n$ is the total number of vertices. If the distance is $r$, then changes to both polygons by Hausdorff distances $< r/2$ will be safe.