Comments on: Find Intersection Point of two lines in AS3

By: Calculating the Distance from a Point to a Line in AS3 | Bacon and Games

Calculating the Distance from a Point to a Line in AS3 | Bacon and Games — Thu, 04 Mar 2010 01:04:32 +0000

[...] again I’ve built on a handy function written by Keith Hair that finds the point of intersection between two lines. Using his lineIntersectLine() function and my getPerpDistanceFromLine() function you can calculate [...]

By: Keith H

Keith H — Sat, 09 Jan 2010 02:05:57 +0000

Thanks to Chris B-B for making it clear to me about a bug in the as_seg part, and preventing future headaches this might have caused me.

By: Keith H

Keith H — Thu, 30 Jul 2009 22:31:08 +0000

Thanks Dennis and everyone else who have been pointing out the as_seg part of the function.
Since it’s only comparing if the value is greater, the actual distance by using square root is not important.

if(as_seg){
if(Math.pow((ip.x – B.x) + (ip.y – B.y), 2) > Math.pow((A.x – B.x) + (A.y – B.y), 2)){
return null;
}
if(Math.pow((ip.x – A.x) + (ip.y – A.y), 2) > Math.pow((A.x – B.x) + (A.y – B.y), 2)){
return null;
}

if(Math.pow((ip.x – F.x) + (ip.y – F.y), 2) > Math.pow((E.x – F.x) + (E.y – F.y), 2)){
return null;
}
if(Math.pow((ip.x – E.x) + (ip.y – E.y), 2) > Math.pow((E.x – F.x) + (E.y – F.y), 2)){
return null;
}
}

By: Dennis

Dennis — Thu, 30 Jul 2009 19:16:47 +0000

Hi there,
thanks for the great piece of code! Just wanted to suggest that you don’t use Point.distance for the “as_sec” part – because I think calculating the distance always uses the square-root – which is calculated slowly.

If you only want to check whether something is nearer than another, it’s enough to compare (a^2 + b^2) for both distances.

Hope I made clear what I mean
(if you want to reply, please also drop a short mail)

Cheers,
Dennis

By: jerobiko

jerobiko — Sat, 04 Jul 2009 19:27:43 +0000

Thank you! It was quite useful

By: takopus

takopus — Fri, 03 Jul 2009 11:05:59 +0000

Thank you!

By: Controul > A quick note on line and segment intersection (as3)

Controul > A quick note on line and segment intersection (as3) — Sat, 09 May 2009 18:15:31 +0000

[...] intersections that have saved me more than a few hours of headbanging. In particular, his line intersection function is a marvelous paste-and-go solution, and I really feel like posting a small optimisation that [...]

By: Rob McCardle

Rob McCardle — Fri, 08 May 2009 16:29:55 +0000

This was really useful, thanks a million

By: Robert Boyd

Robert Boyd — Thu, 09 Apr 2009 05:47:04 +0000

Thanks a million.

By: HIDIHO! » concave shape triangulation: ear cutting algorithm

HIDIHO! » concave shape triangulation: ear cutting algorithm — Thu, 05 Mar 2009 12:44:50 +0000

[...] the way: the segment intersection function comes from Keith Hair’s blog (pretty nice job ): http://keith-hair.net/blog/2008/08/04/find-intersection-point-of-two-lines-in-as3/ I think something can be done to accelerate the ‘as_seg’ section [...]