Geometry Boost List: [ggl] Touching polygons and floating-point

Subject: [ggl] Touching polygons and floating-point
From: Denis Pesotsky (obey)
Date: 2011-03-02 06:45:00

Is there any chance that there will appear function to fix this stuff
in near future? I don't mean fuzzy detection when doing stuff. I mean
something like spikes detection (that you mentioned in your blog)
after doing stuff. I can list all possible cases on picture, if you
want.

2011/2/11 Barend Gehrels <barend_at_[hidden]>:
> Op 11-2-2011 11:19, Denis Pesotsky schreef:
>>
>> Thanks for answer. But I mean a bit other thing. You noticied same
>> thing in your blog ("Precision, the cause of spikes").
>
> Sure.
>>
>> For example, 1st polygon have coordinates like (1, 1) and (4, 2.3)
>> (and 1 more coordinate somewhere) and other have coordinates like
>> (2.1, y1) and (3, y2), where y1 is y coordinate for crosspoint of
>> Line({1, 1} {4, 2.3}) and y=2.1, while y2 is y coordinate for
>> cross-point of same line and y=3. In float-point presentation that
>> points can be not exactly on this line, but very close. Can this
>> result in leaving 2 separate polygons after union?
>>
> In this described case, probably not, using float or double. But it might
> occur, yes. There is no fuzzy detection indeed. I'll come back to this with
> some details.
>
> Barend
>
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