Add polygon areas by roof orientation condition

Question

I have a shapefile with building poligons and a raster file with the roof orientation (0-360º). I would like to assign the orientation to the building shapefile using QGIS. I converted the raster file to vector. My strategy rely on adding columns to the building shapefile assigning the 4 main orientations (N,W,S,E) areas.

One example. "dataframe.shp":

and vector file of the orientation (with the attribute table presenting the orientation values in º) '"orientation.shp"' :

With this, what I would like to obtain is 4 columns with the area for each main orientation for each building polygon.

Example of rational -> using field calculator for the south orientaion column:

CASE
    WHEN  "DN">135 and "DN"<225  THEN (SUM AREA OF each polgon within this range inside building polygon)
    Else 0
END

I dont know how to complete the conditional and assign it to each building polygon ('dataframe.shp'). Also, I am afraid that is infesiable for a large dataset.

Answer 1

You can use sum() with a filter, like this:

sum(area($geometry),filter:="DN">135 and "DN"<225 and intersects($geometry,get_feature('buildingpolygon',"buildingid",'thisbuildingid'))

Maybe even simpler if you add the building ids first via an intersection operation and then just use this in an group_by parameter, like:

sum(area($geometry),group_by:="buildingid",filter:="DN">135 and "DN"<225)