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Subject: [ggl] Snapping
From: Barend Gehrels (Barend.Gehrels)
Date: 2009-11-22 13:19:30

Hi Stephen,

Welcome to the list!

> Just started looking at GGL and it strikes me that the feature that is
> always missing from geometry libraries is snapping. Point to point,
> point to line, line to line, line to poly and poly to poly. Line to
> line is the most complex of these where a section of a line may snap
> to another line.
That sounds as very interesting!

> I recently wrote algorithms to do this in 3D using OpenCascade for a
> UK based spatial data management company. I'm wondering if there would
> be any interest in adding something like this to GGL or is it just me
> that wants this?
You mean something like: ggl::snap(geometry_from, geometry_to,

I think it can be very useful. For many things it is difficult to
determine where it fits. I think it can be an "extension" (GGL has now
an extension model). But it is applicable for more than GIS only. So
might be an "snapping" extension or "editing" extension. Ideas?

The only thing I don't understand exactly, is why line/line is more
complex than poly/poly.

Regards, Barend

p.s. for your information,
1) GGL is currently under Boost Formal Review, which officially ends
today (but the report will take somewhat longer)
2) until GGL is accepted or rejected by Boost, the most recent sources
are hosted at SVN_at_Geodan, which is protected, you can get an account if
you want
3) on acceptance, the SVN will be moved to SVN_at_boost, else (probably) to

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