How to detect if an UIBezierPath intersects itself?

Question

I have an user drawn UIBezierPath and I want to know if it intersects itself. Can anyone point me in a good direction for detecting this?

Thanks!

Here is a good direction.. http://stackoverflow.com/questions/4039229/checking-if-two-cubic-bezier-curves-intersect — iDev, Nov 20 '12 at 23:59
Are you not simply checking if the UIBezierPath is closed or not by your question? — hd1, Nov 21 '12 at 00:42
No, I do not want to check if it is closed. I just want to know if the path intersects itself. Say the user draws something like http://www.mathatube.com/images/pentagon-complex_1_.gif then we have an intersection. — Groot, Nov 21 '12 at 10:25

score 1 · Accepted Answer · answered Nov 21 '12 at 05:24

1

How do you build your path? Is it just an accumulation of straight line segments? If so you could keep a list of those (parallel to your UIBezierPath, that you use for rendering), and then perform line intersection tests. It'll be O(N^2), though, in the naive implementation.

answered Nov 21 '12 at 05:24

Wade Tregaskis

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Thanks, works like a charm! For my purposes O(N^2) is more than enough! – Groot Nov 21 '12 at 14:02
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can i get some code for this line intersection test and this o(N^2) – Anand Feb 14 '13 at 14:19

How to detect if an UIBezierPath intersects itself?

1 Answers1