[Qgis-user] Small maths problem!

[Andrew Harfoot]

Just a thought Richard, but if you don't need to edit the data, could 
you not use a join to add a (precalculated) rotation field on the fly, 
either on the DB side, or in QGIS?

Cheers,

Andy

On 23/07/2015 09:10, Richard McDonnell wrote:
> 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.
>
>
>
> OPW - Ag féachaint don am atá le teacht - Ag caomhnú ón am atá thart
> OPW - Looking to the future - Caring for the past
> <http://www.opw.ie/>
> Email Disclaimer: http://www.opw.ie/en/disclaimer/
>
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user


-- 
Andy Harfoot

GeoData Institute
University of Southampton
Southampton
SO17 1BJ

Tel:  +44 (0)23 8059 2719
Fax:  +44 (0)23 8059 2849

www.geodata.soton.ac.uk

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20150723/eaccd080/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 6095 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20150723/eaccd080/attachment.png>