[mapserver-users] Mapserver tile edge rendering behaviour

[Johannes Paul]

ok I get it ... i use <metabuffer> within Mapcache and the missing border
of my polygon get rendered in the adjacent tile :)
I though that was a problem with Mapserver, but it is just standard
behaviour; it was just a matter of tiling options.
Thanks !
Johannes


On Thu, 12 Mar 2020 at 13:11, Johannes Paul <johannespaul92 at gmail.com>
wrote:

> Hi Steve,
> thanks for your answer.
> Basically, I have the planet emerged lands that are cut-off in square
> polygons. These polygons are stored in postgis, and I use mapcache with a
> mapserver WMS source to tile the layer.
> When I have a polygon ending exactly on the tile edge and the polygon does
> not have adjacent polygons on the top or on the left hand tile, I miss my
> polygon border.
> As explained I made a simple test with a mapserver WMS request where the
> requested bbox would be exactly the bbox of a square polygon, and mapserver
> doesn't render top and left borders of the polygon...
> Could you please tell me more about the options that could be used within
> mapcache or mapserver conf ?
> Thanks,
> Johannes
>
> On Thu, 12 Mar 2020 at 05:08, Steve Lime <sdlime at gmail.com> wrote:
>
>> MapServer uses the center of the pixel but does compensate for models
>> defined by other specs (e.g. WMS, which defines an extent as outer edge to
>> outer edge. Straight CGI (mode=map) will adjust the requested extent based
>> on the image size to ensure that square cells are being used. WMS allows
>> for non-square cells.
>>
>> It’s possible you’re seeing the effect because the requested extent and
>> image size are off just a bit. Would need a little more info to be sure.
>>
>> When tiling you can set edge buffers to deal with this sort of thing.
>> Generally you’d choose a value to match your widest symbol. How exactly
>> you’d deal with this depends on how you’re generating tiles (mapcache,
>> mode=tile, etc...).
>>
>> —Steve
>>
>> On Wed, Mar 11, 2020 at 8:59 AM Johannes Paul <johannespaul92 at gmail.com>
>> wrote:
>>
>>> Hello,
>>> I use a data source (postgis or shapefile, it doesn't matter, the
>>> behaviour is the same), that is made of a simple polygon created from a
>>> bbox, on which is applied a simple 'outlinecolor'.
>>> When calling my URL with a bbox that is *exactly* the size of that
>>> polygon, mapserver only renders the bottom and the right hand edges; top
>>> and left hand egdes are not drawn on my output image!?
>>> When forcing 'WIDTH 2', I do get a thin (1 pixel) outline on the top and
>>> left hand edges, and a thick (2 pixels) on the bottom and right hand edges.
>>> I expect this is related to where mapserver is taking the coordinate
>>> within the pixel (center? corner?), but I'm not sure ? Any option to
>>> overcome that behaviour ?
>>> Thanks in advance.
>>> Johannes
>>> _______________________________________________
>>> mapserver-users mailing list
>>> mapserver-users at lists.osgeo.org
>>> https://lists.osgeo.org/mailman/listinfo/mapserver-users
>>
>>
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