Hi Matt, Thanks, you found a bug :). You can restrict the visibility of layers either by setting scale limits on the actual Layer or by using Min/Max ScaleDenominators in Style Rules. The latter is what is used in osm.xml, and it appears I forgot to add support for this in nik2img. The inspection of every rule for every style in a layer was commented and only the general layer visibility was being reported which is not what you are looking for. So, grab nik2img trunk and this should now be fixed [1].
Dane [1] http://code.google.com/p/mapnik-utils/source/detail?r=1101 On Apr 3, 2011, at 11:37 PM, Matt Kenny wrote: > Hello, > > If this isn't the proper mailing list to post this question, I > apologize in advance. > > I'm currently working with a group of individuals from the Cascadia > Users of Geospatial Open Source (CUGOS) OS-Geo Chapter on creating our > own OSM planet server. We currently have the planet file imported and > updating, and are performing basic rendering using mod_tile + renderd > with mapnik2. > > I'm experiencing some strange behavior in regards to rendering tiles > at low zoom-levels (e.g. Zoom Level 4). Specifically, it appears that > a number of layers are being rendered at these small-scales which > should actually not be rendered based on the 'MaxScaleDenominator' > values in my mapnik2 stylesheet. As all these layers are being > rendered across such a large spatial extent, render times are > extremely long. > > Utilizing Dane Springmeyer's nik2img.py [1] utility in combination > with the osm.xml stylesheet [2] (our version is upgraded for mapnik2 > syntax), I've produced the following log file [3]. AFAIK, a number of > these layers should not be rendering (reported as visible) at > zoom-scale 4. For example, the reported MapScaleDenominator via the > nik2img log is, '22363290.3714'. With this in mind, I went ahead and > searched my osm stylesheet for the 'MaxScaleDenominator' for one of > the layers I assumed should not be rendering at zoom-scale 4, > 'piers-area'. The following snippet shows that the MaxScaleDenominator > parameter has a value much lower then the the reported > MapScaleDenominator at zoom-scale 4. > > <Style name="piers-area"> > <Rule> > <MaxScaleDenominator>200000</MaxScaleDenominator> > <PolygonSymbolizer fill="#f2efe9"/></Rule> > </Style> > > Additionally, this same behavior is occurring using a different > stylesheet, the osm-bright style by AJ Ashton of Development Seed. The > nik2img logfile for the same location and zoom can be found here [4]. > > So... after all that, my questions are essentially: > * Is it correct in assuming that all these layers should _not_ be > listed as visible when rendering an image via nik2img at such a low > zoom-level? > * If so, what might be causing the disconnect between the layers > that nik2img is reporting as visible for this mapscale versus the > layers' own MaxScaleDenominator values in my stylesheets? Could it be > a projection issue? Maybe something I'm introducing during the use of > upgrade_map_xml.py to convert mapnik -> mapnik2 syntax? > > Thanks for any advice. I'd be happy to provide any further > supplementary/clarifying info. > > -Matt > > [1]: http://code.google.com/p/mapnik-utils/wiki/Nik2Img > [2]: http://svn.openstreetmap.org/applications/rendering/mapnik > [3]: http://pastebin.com/QDQ701nZ > [4]: http://pastebin.com/6HMpMvWb > -- > m a t t h e w k e n n y > http://www.mkgeomatics.com > > _______________________________________________ > dev mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/dev _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
