[mapserver-users] Mapserver 6.4 does not draw dense line segments at lower zoom levels. Why?

[Steve Lime]

Hi! My guess is your v.5 style is being interpreted differently in v.6. For
example, what’s the purpose of the ANGLE 360? There were some big changes
between versions 5 and 6. For example you don’t have to use a circular
brush to draw a thick line. You should be able to do something much simpler
like:

  STYLE
    COLOR 0 0 255
    WIDTH 2
  END

—Steve


On Mon, Mar 2, 2020 at 4:48 PM Ei Fujioka <efujioka at duke.edu> wrote:

> Hello all,
>
> I'm upgrading a web site that I have been developing for many years. The
> web site uses Mapserver & Mapscript along with PHP. Mapserver layers are
> drawn on top of Google Maps using Javascript.
>
> What I'm struggling to figure out is that a line layer is not drawn at
> lower zoom levels with Mapserver & Mapscript 6.4 and PHP 5.4.16. When
> zooming in, the lines will start getting drawn but still not fully.
>
> The same layer was drawn at any zoom levels without any problem under
> Mapserver 5.2 and PHP 5.2.6.
>
> Are there any mapfile settings (new to Mapserver 6.4 or changed from
> Mapserver 5.2) that limit the number of line segments to be drawn at
> unit cell or affects how the lines are drawn at differently zoom levels?
> Are there any limits in Mapscript/PHP regarding data size to fetch or
> draw? The line data of the layer is stored in a PostgreSQL table which
> has a lot of records (~270,000 line segments). If the line layer does
> not have such a large number of records (e.g. ~10,000), it draws fine.
>
> Please take a look at an image (screenshots) that shows how the lines
> are drawn differently between Mapserver 5.2 and Mapserver 6.4:
> http://seamap.env.duke.edu/images/mapserver6_4_not_draw_lines.png
>
> The new web site is not publicly available yet, so I can't let you
> explore but the existing web site that draws the example line layer fine
> can be accessed at
> http://seamap.env.duke.edu/dataset/2001
> # Please turn on "Survey tracks" in the Layer selection.
>
>
> The snippet of the mapfile is below.
> Thanks for your help in advance!
>
> Ei Fujioka
> Duke University
>
>
> === Mapfile ===
> MAP
>    EXTENT -20001364 -15000982 20001253 15000982
>    IMAGETYPE "PNG"
>    NAME "OBIS-SEAMAP_OGC_SERVICES"
>    SIZE 256 256
>    STATUS ON
>    TRANSPARENT TRUE
>    UNITS METERS
>
>    OUTPUTFORMAT
>      NAME "PNG"
>      MIMETYPE "image/png"
>      DRIVER "AGG/PNG"
>      EXTENSION "png"
>      IMAGEMODE RGBA
>      TRANSPARENT TRUE
>    END # OUTPUTFORMAT
>
>    PROJECTION
>      "init=epsg:3857"
>    END # PROJECTION
>
> SYMBOL
>    NAME "solid_line"
>    TYPE ELLIPSE
>    POINTS
>      1 1
>    END
>      FILLED true
> END
>
>    WEB
>      IMAGEPATH "/var/www/tmp/"
>      IMAGEURL "/tmp/"
>      METADATA
>        "wms_srs"    "EPSG:3857 EPSG:4326"
>        "ows_enable_request"    "*"
>        "wms_title"    "Online Mapper"
>      END # METADATA
>    END # WEB
>
>    LAYER
>      CLASSITEM "classitem_dataset"
>      CONNECTION "user=xxx password=xxx dbname=xxx host=xxx"
>      CONNECTIONTYPE POSTGIS
>      DATA "geom from (SELECT ..., as classitem_dataset, 'solid_line' as
> symbol FROM z_tracks WHERE ...) AS foo USING UNIQUE oid USING SRID=4326"
>      METADATA
>        "wms_legend_graphic"    "true"
>        "gml_featureid"    "oid"
>        "title"    "Survey tracklines"
>        "gml_include_items"    "all"
>        "wms_title"    "Survey tracklines"
>      END # METADATA
>      NAME "survey_tracks"
>      PROJECTION
>        "init=epsg:4326"
>      END # PROJECTION
>      STATUS OFF
>      TILEITEM "location"
>      TOLERANCE 1
>      TYPE LINE
>      UNITS METERS
>      CLASS
>        NAME "class_0"
>        EXPRESSION "0_ON"
>        STYLE
>          ANGLE 360
>          COLOR 255 0 0
>          OUTLINECOLOR 255 0 0
>          SIZE 2
>          SYMBOL [symbol]
>        END # STYLE
>      END # CLASS
>
>      # In total 60 CLASS ... END are defined
>    END # LAYER
>
>
> --
> ========================
>    Ei Fujioka
>    Research Scientist
>    Nicholas School
>    Duke University
>
>    (919) 684-3518
>    efujioka at duke.edu
> ========================
>
> _______________________________________________
> mapserver-users mailing list
> mapserver-users at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/mapserver-users
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