[postgis-users] ST_OffsetCurve

[Sandro Santilli]

On Wed, Jun 29, 2011 at 11:17:39AM +0200, Stephan Holl wrote:
> Andreas Neumann <a.neumann at carto.net>, [20110629 - 11:11:33]

> >  I hope that someone else can pay for the single-sided buffer to be 
> >  available in Postgis? Any takers?
> 
> I thought that this was included in the estimation from strk as well?
> The initallay mentioned patch provided this already, but needs to get
> reworked as well as added tests and documentation.

The problem arised from a confusion about the term "single-sided buffer".
Rafalmag, author of the initial patch, called "single-sided buffer"
a function that would return a line, not an area. 

Such a lineal output was (by Martin Davis of JTS, Paul and me) seen as
best called "offset curve" instead, whereas "single-sided buffer" would
be a function returning an area instead. See the first comments exchange
on http://trac.osgeo.org/postgis/ticket/413

Later on Martin implemented proper "single-sided buffer" (areal) in
JTS, which I ported to GEOS-3.3.0 as far as to the C-API, where I also
exposed a proper "GEOSOffsetCurve" with a good signature to replace
the badly named "GEOSSingleSidedBuffer" on which rafalmag patch is based.

--strk; 

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