I have 3 layers that sometimes have overlapping features. I need to use a thin outline style to interpret the area within the polygon and want to be able to see on the map when the features overlap. Think of it as 3 identical polygons. How can I style this?
You can set each layer to render differently when there is an overlap with another layer. Go to the style, expand
layer rendering, then select
layer blending mode.
If you want to see overlaps with polygons from the same layer, you could (also) set the
feature blending mode to multiply.
I use the 'Line Pattern Fill' with a different colour and line fill rotation for each layer.
It can be useful to create a variable in the project properties to use as the spacing between lines, fill line weight etc, this will make it easier to adjust all layers by changing one or two variables instead of lots of variables for different layers.
See below for examples:
As another option, you may be able to add a layer dedicated to show the overlapping area, so that you can keep original three polygon layers, showing thin outlines only.
Run Build virtual vector tool (in
QGIS Processing Toolbox > Vector general), with
Create Unioned VRT option.
Put the newly created layer underneath and set color and transparency.