unwanted tile boundaries

[Ken-ichi]

Hello again,

With Mike's help I got Tilestache to render things (yay), but now I'm
finding that my attempts to style polygon borders end up styling the
borders of their tiles as well. I assume this is because Tilestache
is rendering the portion of the polygon that lies within the tile,
including the tile border, but is there a way to avoid this with
Polymaps or through Tilestache configuration? None of the Polymaps
examples seem to show this, so I was wondering if I'm just missing
some Tilestache vector provider configuration or something. I would
like the polygons to appear seamless across tiles.

My apologies if this is a Polymaps issue, but the Polymaps Google
Group seems dominated by spammers.

Here's my code and a screenshot:

https://gist.github.com/1091334
http://dl.dropbox.com/u/15717/tile_boundaries.png

-ken-ichi

[Nathaniel Kelso]

> Ken,

I find it convenient to render boundary lines in addition to feature
polygons to work around this.

Alternatively, you can use TileStache tiles as feature index only,
then pull appropriate feature geojson and render on map. See:

http://www.washingtonpost.com/wp-srv/special/nation/census/2010/

Sent from my handsful device.

[Ken-ichi]

Thanks for the suggestions, Nathaniel, but surely there's another way
around this issue, right? The Polymaps examples that use vector tiles
don't seem to do anything like this, so presumably the tile server
they're using returns somewhat different data. For example:

http://polymaps.org/ex/statehood.html

I was hoping there was a way to get Tilestache to do the same.

-ken-ichi

[Michal Migurski]

Hi Ken-ichi,

Polymaps buffers their vector tiles out somewhat, and uses masks to hide the edges that you can see. I talked to Nate about a way to correct for this in Tilestache, and my plan is to change the Vector provider to make it easy to generate buffered, clipped tiles. Basically you'd get a bit of extra data around the edges but Polymaps would hide that from you. I think this would have the correct effect and be more like the Polymaps example.

-mike.

----------------------------------------------------------------
michal migurski- mi...@stamen.com
415.558.1610

[Ken-ichi]

Hey Mike,

That would be great! So I take it you don't actually use Tilestache
to serve vector tiles of polygon data in your current projects? Seems
like the borders are a serious limitation.

-ken-ichi

[Michal Migurski]

Hi Ken-ichi,

We do use it, but so far mostly just for line strings instead of polygons so we've not run into this problem. I made the change, still would like to address Marko's concern with the points before pushing version 1.18.0:
https://github.com/migurski/TileStache/commit/16916e2e

-mike.

[Ken-ichi]

Beautiful, this works great. I had hacked some buffering in myself
just for testing, but this is much better. Thanks!

-ken-ichi