[Qgis-user] (re)colloring overlapping parts of multipolygons

Richard Duivenvoorde rdmailings at duif.net
Sat Jun 19 13:23:55 PDT 2021


Thanks all for the tips,

I was indeed hoping I could stick to geometry generation only and then in one way or another split up the parts of the multipolygons...

But receiving the actual setup now (see attached), my conclusion is now indeed to do some processing steps, either vector or raster based... ( though doing the geometry generation was fun ;-) )

Again, thanks all for the input!

Richard

On 6/19/21 4:45 PM, Richard Duivenvoorde wrote:
> 
> 
> Hi List,
> 
> I'm experimenting to create 'flower'-shaped polygons for a point layer, denoting the signal coverage of several directional radio transmitters on a pole (fyi: to find/locate bats with small transmitters).
> 
> After some fiddling I came to the attached result for a point with 3 (but dynamic from attribute) transmitters using the following expression:
> 
>  collect_geometries(
>  array_foreach( string_to_array("azimuths"),
>  make_circle( make_point(
> 		$x + "bereik_m"/2 * cos(radians(@element)),
> 		$y + "bereik_m"/2* sin(radians(@element))), "bereik_m" )
> 		))
> 
> The result being a multipolygon with overlapping parts.
> 
> In this work the overlapping area'a are (apparently) the most interesting, as there the 'location' accuracy is highest.
> 
> So my question: is there a way to give the overlapping area's really different colors.
> I've been playing with the layer rendering options, but ideally the area's in which there is no, 2 parts, 3 parts, and 4 parts overlapping should be differently colored..
> 
> I could try to create more advanced expressions (or probably I would go for some python) for that, but I was hoping maybe there is another trick/idea to use current multi-polygons, without adding 'parts'
> 
> Any help/tip is appreciated.
> 
> Regards & TIA,
> 
> Richard Duivenvoorde
> 
> 
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