[postgis-devel] RFC - Orientation checking and forcing functions

[Daniel Baston]

OK, so some alternatives I see are:

1) rename the functions to more clearly indicate that they only consider
polygons (ST_ForcePolygonCW, ST_IsPolygonCW ? )
2) modify new functions and ST_ForceRHR to also consider orientation of
closed LineStrings
3) modify new functions to also consider closed LineStrings, without
modifying ST_ForceRHR

I don't like the idea of modifying ST_ForceRHR, since it has existed
forever, and modifying this would also suggest changes to ST_ForceLHR,
whose implementation is contained within SFCGAL.

I'm inclined towards #1.  Do people have any thoughts on these
alternatives, or maybe a different solution?

Dan

On Wed, Feb 8, 2017 at 6:26 AM, Sandro Santilli <strk at kbt.io> wrote:

> On Tue, Feb 07, 2017 at 07:55:27PM -0500, Daniel Baston wrote:
>
> > Non-polygonal geometries, including closed LineStrings, are
> > simply passed through.
>
> This is the part I don't like. A closed LineString is really the
> only geometry that can be strictly clockwise or clounterclockwise
> (while polygons want shells and hole in opposite directions) so
> I find it counter-intuitive for ST_IsCW and ST_IsCCW to both return
> true for them, and for ST_ForceCW and ST_ForceCCW to return them
> untouched.
>
> --strk;
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-devel/attachments/20170208/9db3548f/attachment.html>