[OSM-dev] [OSM-talk] 1) Messy Overlapping 2) Messy Layers 3) Bridges 4) Trunk/primary 5) Forum

[80n]

Moved from talk to dev.

On 2/11/07, Jochen Topf <jochen at remote.org> wrote:
>
> On Sun, Feb 11, 2007 at 12:09:42PM +0000, 80n wrote:
> > On 2/11/07, Tom Chance <tom at acrewoods.net> wrote:
> > >
> > >Ahoy,
> > >
> > >On Sunday 11 February 2007 00:53:25 Ben Robbins wrote:
> > >> 5 problems I have...please split up into seperate topics for
> > >reply.  Check
> > >> image for refernces..
> > >>
> > >> http://i57.photobucket.com/albums/g226/ben_robbins_/osm3things.png
> > >>
> > >> 1)  Where different highway types meet at junctions it usually
> renders
> > >> quite a messy overlap of the core where 1 of the cores renders later
> and
> > >> has a rounded end.  In just adding an additional tag (for the purpose
> of
> > >> the example I have added core=yes) you can make selected cores render
> > >again
> > >> later and clean up junctions.  What would a good tag for this be?
> > >or...are
> > >> there better methods of sorting out this asthetical fault?.
> > >
> > >If things look wrong in the slippy map or your own Osmarender renders,
> > >don't
> > >tag your way around the problems! Report the problems with mapnik and
> > >osmarender and wait for them to be fixed, but keep the tags in the
> > >database
> > >clean.
> >
> >
> > Actually this kind of experimentation and innovation should be
> encouraged.
> > If people play with rules files and demonstrate potential solutions,
> that's
> > a much more constructive approach than submitting a fault to trac and
> then
> > wondering when it will get fixed.
> >
> > I think the core=yes modification is quite interesting.  The end result
> > looks good and is an improvement - but maybe there is a better way to
> > implement it.  Now that Ben has demonstrated how good it looks, I think
> we
> > are at least one step closer to a solution.
>
> Generally there is no need for the core=yes element. As far as I can see
> the problem only occurs in T-shaped junctions (or topological similar)
> where the through road has a "lower classification" than the ending road.
> So if there is a primary road ending at a T-junction and the
> unclassified road goes through the same junction, you'll see the ugly
> round knob in the junction. But it certainly is computationally possible
> to find those T-junction cases and re-order the drawing of the ways.
>
> Problem is: This gets messy once we are not only looking at one junction
> but at a whole road network, and it gets really messy once we take layers
> into account. But I don't see how the core=yes helps here. It only makes
> things more complicated. Certainly for the person doing the tagging.


Ben's solution is to tag a short section of the unclassified road as
core=yes.  This causes it to be re-rendered after the core of other more
major roads have been rendered.

The approach is not dissimilar to the way that layers work, except its only
within the road rendering section.

It's elegant because it keeps the rendering engine simple, the results are
better and the presence of an extra tag is non-invasive.  Other renderers
can ignore it and osmarender can ignore it when a better solution is found.

I think I'd prefer the tag to be renderCoreLast=yes as this makes it a
little clearer than just core=yes.

It's unwise to be critical of people who are doing innovative things with
osmarender rules files unless we actually have something better to offer.  I
know Ben has a very fine eye for detail and cares a lot about the appearance
of his maps.  He has done something interesting here to solve a small
problem that we have not yet paid attention to in osmarender.


And another reason why the core-thing is an ugly hack that doesn't even
> work: It only works as long as the highway casing is always the same
> size. See the enclosed png for an illustration of the problem.
>
> The core of the problems seems to be that we assume that road junctions
> are point objects and have no size. But thats not the case once you draw
> roads which have a width.
>
> btw: The google map rendering has the same problem. Sometimes it is even
> worse, because sometimes they not only have the ugly round core thing,
> but the casing is drawn on top also. See for instance just south of the
> Golden Gate bridge the short stretch of highway 1. (Problem appears only
> in some zoom levels.)



Jochen
> --
> Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/
>   +49-721-388298
>
>
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