Getting the same fill patterns on different layers to match (set common base point) in QGIS

Question

I got a similar problem as described here: Using multiple line fill patterns with common base point in QGIS

I want two layers with the same symbology to overlap seamlessly. However, it looks like this:

However, in my case, the symbologies are on two or more different layers, so a geometry-generator doesn't seem to do the trick.

Any suggestions?

Answer 1

I did solve it with the solution from @jake:

You can use a geometry generator that adds a common point to all geometries, so all patterns have the same origin: union($geometry, make_point(-180,-90)). The coordinates used in make_point() need to be to the south west of all of your features.

Answer 2

You can aggregate the geometries of each layer and than combine them using collect_geometries(). The final expression could look like this - replace 'poly1', 'poly2' etc. with the names of your polygon layers:

collect_geometries( 
    aggregate('poly1', 'collect', $geometry),
    aggregate('poly2', 'collect', $geometry),
    aggregate('poly3', 'collect', $geometry)
)

Screenshot 1: original polygons (3 layers):

Screenshot 2: the collected polygons with a common line-pattern: