Re: [Boost-users] [Polygon] Test among 3 libraries

Subject: Re: [Boost-users] [Polygon] Test among 3 libraries
From: Angus Johnson (angus_at_[hidden])
Date: 2010-09-08 20:13:53

> That's a worthwhile goal to be sure. When I discussed scalability I 
> meant algorithmic complexity and ability to process large data volumes 
> in input geometry in a single test case. 
Ahh, thanks for the clarification. I haven't yet done any significant 
testing of processing very large data volumes, nor am I competent to 
determine an O value, so I'll defer to your estimation there.

>  Also, I believe GPC does handle high order intersections because I'm 
> quite certain I was generating large numbers of them in the tests I 
> was running that GPC seemed to handle just fine. I could be wrong of 
> course, but I suggest you double check that GPC doesn't properly deal 
> with complex intersection. I know it doesn't deal with overlapping or 
> self intersecting polygons at all, but that is a separate issue from 
> polygons that have vertices in common or polygons that abut along 
> edges but do not overlap. GPC is used quite extensively and paid for 
> by many people, we should be responsible about making claims about its 
> short comings.

I was careful to qualify my statements about GPC with "I don't think" 
and "I believe". However, I accept that this still isn't fair treatment 
and I should be sure before making these claims. Let me simply state 
that under my stess-testing, GPC fails about 4% of the time (and with 
extreme stress testing - rounding random vertices to nearest 100 instead 
of nearst 10 - it fails far more frequently). The full source code for 
my stress-tests can be downloaded here: 
http://www.angusj.com/delphi/clipper.php