[mapserver-users] GAP problem on MapServer 6.0.1

[Havard Tveite]

I have been able to reproduce this problem with trunk.
It seems to occur for gap lengths that are longer than
the length of the line.  In that case, the arrows are
rendered for each line segment from the middle of the
line to the end of the line.  Slightly different
behaviour for 6.0 and trunk.

I have filed a ticket (http://trac.osgeo.org/mapserver/ticket/4120).

Håvard

On 11/10/2011 9:49 AM, Håvard Tveite wrote:
> Dear Jackey Cheung,
>
> I am not sure what exactly you are trying to achieve.
> Your arrows seem to point in the direction of the lines.
> The topmost arrow in figure 1 is placed at a strange
> position - is that the problem?
>
> Some comments:
>
> The result shown in image 2 is expected.  The arrow
> symbols are in this case placed at the start points of
> the lines according to the centre point of the symbol's
> bounding rectangle (except 0,0 is always taken as the
> upper left corner of the bounding rectangle).
> When using a negative GAP, the direction of the symbol
> is the direction of the line at the (end)point.
> In version 6.2, ANCHORPOINT is introduced to make it
> possible to specify a different anchor point for the
> symbol (http://mapserver.org/trunk/mapfile/symbol.html).
>
> The centre point of the bounding box of your arrow_right
> symbol will be at (17.5,7) in the symbol's coordinate
> system, so the arrows will be placed somewhat shifted to
> the right (in the direction of the arrow).
> In 6.0, if you want the ends of the arrows to be aligned
> with the start of the lines (when using geomtransform
> start), you could use the following symbol:
>
> SYMBOL
>     NAME "arrow_right_shift"
>     TYPE VECTOR
>     POINTS
>       30 6
>       52 6
>       50 0
>       60 7 # why 7.5?
>       50 14
>       52 8
>       30 8
>       30 6
>     END
>     FILLED TRUE
> END
>
> In 6.2, you will be able to specify this using
> ANCHORPOINT 1 0.5
>
>
> Håvard
>
> On 11/10/2011 06:35 AM, Jackey Cheung wrote:
>> Hi all,
>>
>> We are trying to render line direction on 6.0.1. However, there are
>> something weird with it.
>>
>>
>> SYMBOL
>>     NAME			"arrow_right"
>>     TYPE VECTOR
>>     POINTS
>>       5 6
>>       27 6
>>       25 0
>>       35 7.5
>>       25 14
>>       27 8
>>       5 8
>>       5 6
>>     END
>>     FILLED  TRUE
>> END
>>
>>
>> LAYER
>>     NAME              "traffic_direction"
>>     STATUS            DEFAULT
>>     TYPE              LINE
>>     MAXSCALEDENOM     5000
>>
>>     CONNECTIONTYPE    POSTGIS
>>     PROCESSING        "CLOSE_CONNECTION=DEFER"
>>     CONNECTION        "host=xxxxxxx dbname=******* user=xxxxxxxxxx
>> password=************"
>>     DATA              "geom FROM view_render_traffic_direction USING
>> UNIQUE oid USING SRID=4326"
>>
>>     CLASS
>>       NAME            "Traffic Direction"
>>       STYLE
>>         ANGLE         AUTO
>>         SYMBOL        "arrow_right"
>>         SIZE          6
>>         COLOR         0 0 250
>>         GAP           -200
>>         #GEOMTRANSFORM "start"
>>       END
>>     END
>> END
>>
>>
>> The layer above is rendered as 1.PNG. We've checked that there are
>> only one line (ring) there, but arrows are rendered problematic.
>> Then we've tried to change GEOMTRANSFORM to "start" or "end", then
>> rings seem OK, but all arrows at intersections got crossed, as 2.PNG.
>> We've also tried to use OFFSET and GAP with positive and negative
>> combinations, but none can solve the problem.
>>
>> Can anyone shed some light for us? Thanks in advance.
>

-- 
Håvard Tveite
Department of Mathematical Sciences and Technology, UMB
Drøbakveien 31, POBox 5003, N-1432 Ås, NORWAY
Phone: +47 64965483 Fax: +47 64965401 http://www.umb.no/imt/