[geos-devel] Buffering of invalid polygon seems to produce a less useable result

[Casper Børgesen (CABO)]

Hi Sandro.

Thank you for your answer. As far as I have checked, I'm starting out with valid geometries only. So if valid inputs guarantees valid output, I guess I have to go bug hunting.

Regards, Casper

-----Original Message-----
From: geos-devel-bounces at lists.osgeo.org [mailto:geos-devel-bounces at lists.osgeo.org] On Behalf Of Sandro Santilli
Sent: 1. oktober 2014 16:56
To: GEOS Development List
Subject: Re: [geos-devel] Buffering of invalid polygon seems to produce a less useable result

On Mon, Sep 29, 2014 at 07:05:28PM +0000, Casper Børgesen (CABO) wrote:

> Are there any methods to better ensure validity of geometries 
> resulting from the various geometric functions?

By contract, if the inputs are invalid, the output are not guaranteed not only to be valid but also to be computable.

A valid input should always result in a valid output, or it would be a bug.

Turning an invalid geometry to a valid one can be tricky, you may want to look at the ST_MakeValid funcition in PostGIS to see how it is implemented.

--strk; 

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