[Qgis-developer] New angular renderer

[Hugentobler Marco]

Hi all,

In the long term it would be good to have a new plugin type for renderers to make it easier to add support for special needs in visualisation. Up to now, we have provider plugins, GUI plugins and in the diagram branch there are overlay plugins. A renderer plugin would basically provide methods to return a renderer and a method that returns a dialog to enter the settings for this renderer. The QGIS main application could then (at runtime) look what renderers are available and embed their specialised dialog types into the vector layer properties.

Cartographic signatures may differ in colour, shape, texture, saturation, direction and size and each one may describe a different variable. Therefore I think it would be a good way of code reusing if renderers could be connected such that we have a chain where renderer A sets colour according to variable X and renderer B direction according to variable Y (and maybe more...). I'm also going to ask people at my workplace (we have some cartographic experts here) how they would handle such multivariate visualisation.

In the short time, it could be a general renderer option. As Tim suggests, it could be integrated in the new symbology dialogs in Tims patch? I already tested them and like their layout very much.

>b) implement SVG css and a convention for our svg files to that we can
>dynamically colour them

+1

>a) get rid of the 'fixed' symbols (currently the only ones that allow colouring)

I'd vote to keep them. Because they describe the so-called 'well-known symbols' that are usefull to be compatible with several standards, e.g. SLD.


Regards,
Marco  


-----Ursprüngliche Nachricht-----
Von: qgis-developer-bounces at lists.qgis.org im Auftrag von Tim Sutton
Gesendet: Mo 10.12.2007 16:31
An: Michaël Douchin
Cc: qgis-developer
Betreff: Re: [Qgis-developer] New angular renderer
 
Hi

2007/12/10, Michaël Douchin <michael.douchin at laposte.net>:
> Hi !
> I think this renderer goes in a good direction
> I am personaly trying to find a way to draw arrows for each of my point
> , with the angle corresponding of the wind direction. I think this
> fonctionnality should not be used as a "unique value", "continuous
> renderere", etc. symbol type, but separatly, as it is done for the
> labels : we must be able for example to draw the points with
> * a colour depending of one column (eg "boat speed" from green to red),
> * a label representing another column (eg "name of the boat"),
> * and another symbol like arrows (or anything else) drawn from the point
> with its angle contained in another column (eg "wind direction"). The
> best would be to have the possibility of changing the length of the
> arrow with another column (eg "wind speed").
>
> What do you think ?

Yes that makes sense to me too - so basically make symbol rotation an option
on all renderertypes when they are rendering point symbols.

For dynamically colouring symbols my hope / plan was that we can

a) get rid of the 'fixed' symbols (currently the only ones that allow colouring)
b) implement SVG css and a convention for our svg files to that we can
dynamically colour them

Anybody looking for a bit of diversion? - the above would be a great
contribution...



Regards

Tim

>
> Michael
>
> Magnus Homann a écrit :
> > I got inspired be the eVis plugin (great!) and took the liberty of
> > hacking a new renderer, called angular renderer.
> > With it, you can select a column that determines which angle the symbol
> > should have:
> >
> > Screenshot:
> > http://img264.imageshack.us/my.php?image=angularif2.png
> >
> > It's very much like the single symbol renderer, only this extra field
> > for determining which column keeps the direction angle.
> > In fact, my changes should maybe be incorporated into Single Symbol instead?
> >
> > Looking at the rendering implementation, perhaps it would be good to
> > make a renderer interface similar to plugin/provider, so that qgis finds
> > a catalog of renderers? Is this perhasp the same thing that is being
> > done in diagram-branch? Don't know much about that, though.
> >
> > I can see a couple of options
> > a) Change Single Symbol to include angle.
> > b) Add another hard-coded renderer for angular symbol (as shown in
> > screenshot)
> > c) Make the interface for renderers a bit more general, but still
> > require them to be compiled with Qgis. A new renderer requires just two
> > more files.
> > d) Create a new render DLL interface.
> > e) Make renderer and diagram overlay the same stuff (no idea if this is
> > possible).
> >
> > The order is how I prefer to do it. a) -c) I can manage myself, but
> > d)-e) requires knowledge and stamina I might not possess. :-)
> >
> > Magnus Homann
> >
> > _______________________________________________
> > Qgis-developer mailing list
> > Qgis-developer at lists.qgis.org
> > http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-developer
> >
> >
> >
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>


-- 
Tim Sutton
QGIS Project Steering Committee Member - Release  Manager
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