[Qgis-user] Small maths problem!

[Richard McDonnell]

Hi,
I am in need of some guidance, I am trying to create an "active 
hatch/Fill" as part of a style im working on. What I want is for a hatch 
to rotate depending on the orientation of a Polygon.
For example, here is the same entity rotated, with the hatch rotating.


The issue is I am working on a database, onto which I cant add any data 
(additional columns) to the tables, I would like to do this from within 
the styling.
You can use an expression to denote the angle, so I was hoping to do it 
that way.
I was looking to utilize the geometry of a bounding box, and calculate 
the angle of the diagonal, using something like

180*atan((ymax - ymin)/(xmax - xmin))/$pi + 90

But I am not having any luck....If there is no way at present to do 
this, Might I put it forward as a possible new feature?

Regards,

Richard.




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