[Mapserver-dev] Rotated Map Rendering

[Daniel Morissette]

Steve Lime wrote:
> Will people really be moving between rotated and non rotated worlds? The
> more
> important question is will angles change throughout the course of
> interacting with
> an app. 

We could easily imagine a vehicle tracking app where the rotation of the 
map is driven by the direction of the vehicule.

However, even if for apps where the rotation doesn't change, I think it 
will be easier to make reusable code that works in both rotated and 
non-rotated if we go with #1 since all the code deals with extents 
before rotation.

(e.g. something like chameleon would have to have exceptions coded in it 
to deal with scale/extents changes induced by cases #2 and 3, but Iam 
hoping that #1 would save us from that)


> If so then thats a strong argument for 1. If angles are fixed
> then I still like
> 2, since at least scale would be constant from map to map.

Actually, my understanding was that only #1 would maintain scale (and 
cellsize) from map to map.  With #2 or #3, the scale would vary for a 
given extent depending on the rotation angle, and predicting the 
resulting scale would be a complex calculation. However with #2 and #3 I 
believe the scale/cellsize would be constant from map to map as long as 
the rotation angle doesn't change, but would still be hard to calculate.

Daniel
-- 
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  Daniel Morissette               dmorissette at dmsolutions.ca
  DM Solutions Group              http://www.dmsolutions.ca/
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