[mapserver-dev] SYMBOLTRANFORM for special symbols rendering

[Brent Fraser]

Ahh, this works:
http://mapserver.org/trunk/development/rfc/ms-rfc-78.html

this doesn't
http://mapserver.org/development/rfc/ms-rfc-78.html
(darn Google...)

Best Regards,
Brent Fraser


On 11/24/2011 11:57 AM, Alan Boudreault wrote:
> Mainly yes, but might be apply to any other cases. hmm.. I see the 
> graphic properly in the rfc...
>
> http://mapserver.org/trunk/development/rfc/ms-rfc-78.html
>
> Alan
>
> On 11-11-24 12:46 PM, Brent Fraser wrote:
>> Alan,
>>
>> I'm assuming this is mainly for Vector Field Rendering? (I get a broken
>> link for the graphic in the RFC)
>>
>> Best Regards,
>> Brent Fraser
>>
>>
>> On 11/24/2011 9:25 AM, Alan Boudreault wrote:
>>> Hi devs,
>>>
>>> A while ago, it has been discussed about a new way to render a symbol,
>>> which in this case is an arrow. The need is to be able to draw the
>>> body arrow (a line) scaled depending of a value (ie, the magnitude in
>>> vector field) but to not scale the arrow head.
>>>
>>> Mike, Daniel and Thomas discussed this problem in Denver during FOSS4G
>>> and they came up with the concept of ARROWBODY and ARROWHEAD. Those
>>> concepts are essentially to determine what need to be scaled.
>>> Following a discussion this morning.. here's the approach we would
>>> like to use:
>>>
>>> * We define two symbols: the arrow body and the arrow head.
>>> * The arrow head symbol needs to have the ANCHORPOINT set to the head.
>>> * We define 2 styles: one for the body and the other for the head.
>>> * The two style would use a new option: SYMBOLTRANSFORM, which is to
>>> draw the symbol correctly (scalable of not).
>>>
>>> Mapfile example:
>>>
>>> SYMBOL
>>> NAME "arrowbody"
>>> TYPE vector
>>> FILLED true
>>> POINTS
>>> 0 0
>>> 1 0
>>> END
>>> END
>>>
>>> SYMBOL
>>> NAME "arrowhead"
>>> TYPE vector
>>> FILLED true
>>> ANCHORPOINT 0.25 0
>>> POINTS
>>> 0 0.25
>>> 0.25 0
>>> 0 -0.25
>>> END
>>> END
>>>
>>>
>>> # in the layer definition....
>>>
>>> STYLE
>>> SYMBOLTRANSFORM arrowbody
>>> WITDH 1
>>> SIZE [uv_length]
>>> ANGLE [uv_angle]
>>> END
>>> STYLE
>>> SYMBOLTRANSFORM arrowhead
>>> SYMBOL "arrowhead"
>>> ANGLE [uv_angle]
>>> OFFSET [uv_length] 0
>>> SIZE 4
>>> END
>>>
>>> In the arrowhead, we *NEED* to pass the length of the arrowbody (via
>>> OFFSET), since it will be used to determine where the arrow head
>>> should be positioned. the SYMBOLTRANSFORM arrowhead option would tell
>>> the symbol renderer TO NOT scaled the symbol in length. In this
>>> example, we use the terminology arrowbody/arrowhead.... but we are
>>> going to use generic terms to use that feature in other cases.
>>>
>>> I'm glad to hear your comments and suggestions about that approach!
>>>
>>> Regards,
>>> Alan
>>> _______________________________________________
>>> mapserver-dev mailing list
>>> mapserver-dev at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/mapserver-dev
>>>
>>
>
>