[geos-devel] Single-sided buffer gives unexpected result

Sandro Santilli strk at keybit.net
Mon Nov 24 01:19:59 PST 2014


On Thu, Nov 13, 2014 at 01:48:35PM +0100, Paul Meems wrote:
> I have this linestring:
> LINESTRING(6.59607872405104612 53.00390260763848715, 6.5970405434596513
> 53.00362892273712845, 6.59798287063396227 53.00336078433459619,
> 6.59864650169724065 53.00303357725661613, 6.59938686388177764
> 53.00283982209050748, 6.60119220843164101 53.00211012469529948,
> 6.60112679624460608 53.00208460961093948, 6.60026057476097616
> 53.00174672587350244, 6.58878962886061181 52.99727229739764311)
> 
> I create a single-sided buffer of -9E-10 (-70m) with flat endcaps and round
> joinstyle.
> This should create a polygon left of the line.
> But it creates a buffer as in the attached image. You can see that in the
> right corner the polygon is also at the right of the line. This happens
> only at sharp corners.
> Am I forgetting a setting or something?

It sounds like a bug to me. Would be useful to check the same input
against JTS to see if the bug is there or in the port. In any case
the first step would be to file a ticket. NOTE: chances are a similar
ticket already exists so please add your case to the existing one if so.

--strk;

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