[postgis-users] function to check if a polygon is convex

[Martin Davis]

Yes, that's a way to check if a polygon is convex.  Not the most efficient,
but currently there's no more direct way (pretty sure).

On Wed, Mar 2, 2022 at 1:38 PM B H <hemantbist at gmail.com> wrote:

>
> select st_equals(st_convexhull(wkb_geometry), wkb_geometry) is true  for
> all st_isvalid convex polygons I tried on).
> Is this a correct way to check for convexity of the polygon?
>
>
> On Wed, Mar 2, 2022 at 1:15 PM B H <hemantbist at gmail.com> wrote:
>
>> Hi,
>> How do I check if the polygon is convex in postgis?
>>
>> Things I have tried before sending this email
>>  I could not find any function  like st_is_convex.
>> I searched in google but  I could not find any user defined postgres
>> function to check for convexity of polygon either.
>> select st_convexhull(wkb_geometry) = wkb_geometry  -- this returns false
>> for convex polygons also.
>>
>> Other libraries e.g. CGAL seem to have it. So I am hoping that something
>> is already available in postgis that I am missing.
>>
>> https://doc.cgal.org/Manual/3.1/doc_html/cgal_manual/Partition_2_ref/Function_convex_partition_is_valid_2.html
>> Best,
>> HB
>>
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