[mapserver-users] GAP problem on MapServer 6.0.1

[Havard Tveite]

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.