[postgis-devel] ST_AsMVTGeom() feature size limit

[Paul Ramsey]

I can see that using a tolerance of 0 would result in fewer vertices dropped, but isn't the problem I'm seeing a result of 

int preserve_collapsed = LW_FALSE;

??

The original order of 
- remove repeated points
- simplify
- grid
was a performance thing as I recall... 

I'm quite loath to change things without the major users of the tiling coming on board and saying "yeah, great idea!"

P

> On May 18, 2021, at 4:59 PM, Darafei Komяpa Praliaskouski <me at komzpa.net> wrote:
> 
> Hello,
> 
> I had a similar complaint previously and the recommendation I got was that if I want to show more finely grained data on the vector tiles, I should be raising the `extent` value.
> 
> There is a Simplify call at the end of ST_AsMVT that uses the wrong epsilon. It should be 0 instead of 0.5px. Please check this fix: https://github.com/postgis/postgis/pull/463/files - I'd be happy if it gets committed. :)
> 
> On Wed, May 19, 2021 at 1:31 AM Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> I was interested to find that ST_AsMVTGeom drops features that fall below 1/2 a pixel in size.
> 
> postgis30=# select st_astext(st_asmvtgeom('LINESTRING(10 10, 11 10)', 'LINESTRING(0 0, 16384 16384)'::geometry));
>  st_astext 
> -----------
> 
> (1 row)
> 
> There's no configuration option to avoid this behaviour, and if you map a large enough area that your feature size falls below a pixel you end up with big blanks in your map. Have there been no complaints about this before?
> 
> P.
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> 
> -- 
> Darafei "Komяpa" Praliaskouski
> OSM BY Team - http://openstreetmap.by/
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