[Mapserver-dev] Re: Rendering engine enhancements

[Jan Hartmann]

Arnulf Christl wrote:

> Hi,
> we still badly need hatching in polygons with an inclination. We 
> discussed this at the UM in Ottawa. Could someone please tell us where 
> to start in the code, we might be able to do it ourselves. Else: could 
> somebody just get this done and tell me what it will cost us?
> It has to be possible to get the inclination (in degree) from a database 
> and use it as an angle for hatching (most flexible soultion would be a 
> rotatable fill symbol, but also if you come up with something weirdo - I 
> don't care, we just need it soon.
> 
> Don't even start to think about projections - I did and it doesn't make 
> a lot of sense...
> 
> Best regards,
> Arnulf.

Hi Arnulf,

I'm not sure if this will work, but couldn't you use PostGIS with the 
GEOS topological operators? Just create a layer with parallel lines over 
the whole extent, and overlay this with your data layer, so as to cut 
off everything outside the polygons of interest.

I got this idea from something Steve Lime said at MUM2: adding the GEOS 
topological library to MapServer, with the explicit purpose of enabling 
this sort of cartographic functionality. This is a nice idea, for it 
would greatly expand MapServer's cartographic capabilities for all kinds 
of symbolizing. If you get something done along these lines with 
PosTGIS, please let us know. And if it works under PostGIS, but you are 
not able to use PostGIS in a production environment, perhaps some 
funding could be found to implement in in MapServer. Enhancing 
cartographic symbology this way would be interesting, both for 
developers and for paying end users. Having it implemented as a Proof of 
Concept under PostGIS would definitely make it easier to get such funding.

Jan