[Qgis-user] Small maths problem!

[Richard McDonnell]

Andy,
That might just work, I will give it a go...Will let you know how I get 
on, at the moment, I have the style saved to the database, it will be 
interesting to see how that all works!!
Regards,

Richard.



On 23/07/2015 12:36, Andrew Harfoot wrote:
> 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.
>>
>>
>>
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>
> -- 
> Andy Harfoot
>
> GeoData Institute
> University of Southampton
> Southampton
> SO17 1BJ
>
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>
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