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

[Daniel Baston]

The idea was that adding functions with different names would be helpful,
because "RHR" and "LHR" mean different things to different people (and
therefore don't mean much of anything.)

See, for example, the fourth bullet under
https://tools.ietf.org/html/rfc7946#section-3.1.6

Dan

On Wed, Feb 8, 2017 at 2:35 PM, Sandro Santilli <strk at kbt.io> wrote:

> On Wed, Feb 08, 2017 at 11:35:01AM -0500, Daniel Baston wrote:
> > Sorry, I'm not sure I understand which direction you're asking me to
> > pursue.  Are you asking that I write some new functions ST_IsCW and
> > ST_IsCCW that apply _only_ to LineStrings, and then rename the four
> > functions proposed in the PR to something else?
>
> I'd love ST_IsCW, ST_IsCCW, ST_ForceCW and ST_ForceCCW that only apply
> to _closed_ LineStrings, raising an error on anything else.
>
> As for polygons, the only missing functionality I see would be an
> ST_IsRHR, to be a companion to ST_ForceRHR.
>
> I still hadn't checked what ST_ForceLHR does. Hopefully it's just
> the reverse of ST_ForceRHR, in which case we could just make sure
> to make it available even when SFCGAL is not in place.
>
> That said, I remember this whole thing started in an attempt to
> reduce the confusion with the "Right Hand Rule" concept. As I
> agree with you about NOT changing semantic of a very old function,
> I don't see how adding more functions help.
>
> --strk;
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