It generates vector tiles based on WMS requests. MapCache computes the proper
extent based on the requested tile and then kicks off a WMS call for vector
tile. The pull request creates support for a new generic “raw” format. MapCache
doesn’t know much about files in this format, just a mime-type, so things like
metatiling, image processing or tile assembly aren’t supported. You do get the
cache management though. The raw format is not specific to vector tiles so you
could use it for other formats like GeoJSON or UTFGrid.
Anyway, in my mapcache.xml file I have the following setup:
<!—define a new raw format to use for MapBox vector tiles -->
<format name="MVT" type="RAW">
<extension>mvt</extension>
<mime_type>application/vnd.mapbox-vector-tile</mime_type>
</format>
<!—this WMS source fetches MapBox vector tiles (.mvt) -->
<source name="wms_mvt" type="wms">
<http>
<url>http://mapserver.localhost/cgi-bin/mapserv?</url>
</http>
<getmap>
<params>
<LAYERS>sna,wma,lakes,major_roads,places</LAYERS>
<FORMAT>application/vnd.mapbox-vector-tile</FORMAT>
<MAP>/Users/sdlime/work/mvt-demo/demo.map </MAP>
</params>
</getmap>
</source>
<!—and finally the tileset -->
<tileset name="mvt">
<source>wms_mvt</source>
<grid>g</grid>
<cache>disk</cache>
<format>MVT</format>
</tileset>
Then, if you look at the simple.json file in my demo repo you just change the
source for the vector tiles layer to reference MapCache (I was running as
FastCGI) instead of MapServer (mode=tile), so from:
"tiles":
["http://mapserver.localhost/cgi-bin/mapserv?map=/Users/sdlime/work/mvt-demo/demo.map&mode=tile&tilemode=gmap&tile={x}+{y}+{z}&layers=all&map.imagetype=mvt";],
to:
"tiles":
["http://mapserver.localhost/cgi-bin/mapcache.fcgi/gmaps/mvt@g/{z}/{x}/{y}.mvt";]
One thing to note is that you can control the resolution that each tile is
created at. Each tile has a grid associated with it and that is used to convert
the features to a grid-based coordinate system. The higher the resolution of
that grid the more detail is represented in the tile. The default is 4096x4096.
You can change that value via the MVT output format, for example:
OUTPUTFORMAT
NAME “mvt”
DRIVER MVT
FORMATOPTION “EXTENT=512”
END
A smaller resolution or extent will generally result in smaller tiles.
--Steve
From: Miha Požauko [mailto:[email protected]]
Sent: Tuesday, June 26, 2018 3:09 AM
To: Lime, Steve D (MNIT) <[email protected]>
Cc: [email protected]
Subject: Re: [mapserver-users] Status of MVT vector tiles?
I found that pull request before thanks, will play around with it some more.
When you say it relies on WMS requests does that mean it generates raster tiles
or vector tiles in PBD file format? I don't have mine mapcache example working
yet so i don't know what to expect.
About canceled requests i found related "issue" discussed on leaflet forum:
https://github.com/Leaflet/Leaflet.VectorGrid/issues/136
But i don't see a problem with that because all entities are loaded on my map.
I will have to find that secret souce yes, will try to optimize my map file for
different scales. Pregenerated vector tiles would also help.
Thanks for your answers. Will track your github for further updates.
Miha
V V pon., 25. jun. 2018 ob 23:57 je oseba Lime, Steve D (MNIT)
<[email protected]<mailto:[email protected]>> napisala:
Will do. I have a working MapCache example on my dev box that I can share
pieces from. First step is to get MapCache working with the pull-request I
submitted some time ago. It relies on WMS requests to MapServer for the MVT
tiles. Pull request is at:
https://github.com/mapserver/mapcache/pull/166
Regarding the canceled requests:
I'm not sure what up with those. However, I don't believe those are a server
issue, rather a client-based. You can see the same behavior on other sites
using vector tiles from other services
(https://openmaptiles.com/downloads/dataset/osm/#0.23/0/-26) in Chrome
DevTools. Could be related to pre-fetching resources.
Regarding a unresponsive browser:
There's likely a secret sauce in terms of the matching min/max scales you
should offer a layer at, whether you should manage multiple resolutions of your
data on the server and other filtering. The demo is very naïve in that regard
so you can end up with big tiles. At this point it's not something I can offer
a ton of help with - I don’t have a production MVT application yet.
Steve
-----Original Message-----
From: mapserver-users
[mailto:[email protected]<mailto:[email protected]>]
On Behalf Of mp-surv
Sent: Saturday, June 23, 2018 6:28 PM
To: [email protected]<mailto:[email protected]>
Subject: Re: [mapserver-users] Status of MVT vector tiles?
Hey Steve.
I have a working demo using your data and when zooming out not all vector
tiles load and browser becomes unresponsive (image below). To avoid
overloading my computer when zooming out and causing my browser to crash I
would like to use mapcache, but I'm struggling to set it upt. Can you please
give a working example using mapache?
<http://osgeo-org.1560.x6.nabble.com/file/t368111/Capture.png>
I can see there are also a lot of canceled requests but they are not causing
my browser to crash. Do you know what produces them?
Thanks.
--
Sent from: http://osgeo-org.1560.x6.nabble.com/Mapserver-User-f4226646.html
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Lp,
Miha
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