[Qgis-developer] Renderer for vector field data

[Martin Dobias]

On Fri, Jan 8, 2010 at 2:11 AM, Chris Crook <ccrook at linz.govt.nz> wrote:
> I'm wanting a renderer for vector field data.  In my case this is earth
> deformation data - surface displacements - but it could as easily be
> hydrological flow, or other such data.
>
> Ideally this will display an arrow of length and orientation based on data
> values (x,y or length,orientation) at points, but with some independent
> overall scaling to allow all the vectors in a layer to be rescaled without
> recalculating the data.  To be perfect (!) it would also take account of the
> projection convergence when using on the fly projections (though I could
> live without that, at least initially!)

Hi Chris

yes this is all possible with new symbology (introduced in QGIS v1.4 -
will be announced shorly). There are python bindings so you shouldn't
have a problem to create such renderer in python. Unfortunately so far
there are no examples in python, for some code samples you might want
to look at c++ code in src/core/symbology-ng - there are several
renderer implementations and symbol layer types.

For an introduction check this wiki page:
http://www.qgis.org/wiki/Symbology-NG

If you'll need any further assistance, don't hesitate to write to the
mailing list, I'll try to give you some further guidance.

Regards
Martin