[mapserver-dev] Rendering Railroads is slow

[Stephen Woodbridge]

Hi Thomas,

I've been playing with your osm style map and I have noticed the 
rendering railroads tends to be very slow. This is with single line and 
cross ties or with double rail and cross ties.

I realize that part of this is probably because there is much more 
detail involved than rendering other objects, but ...

Any thoughts on how to speed this up. Unfortunately there are not any 
attributes the would allow me to thin the data as I zoom out. One 
thought I had was to add a length attribute and try filtering out very 
short segments, but this runs the risk of gaps. I'll try doubling the 
gap to cut down on the number of cross ties and see how that looks.

Any other thoughts?

Thanks,
   -Steve W

25K scale:

   LAYER
     NAME "RailRoads Z2"
     GROUP "rr"
     STATUS DEFAULT
     DATA "NA/RailRds"
     TYPE LINE
     ##LABELITEM "NAME"
     MAXSCALE 25100.0
     MINSCALE 10100.0
     TRANSPARENCY ALPHA
     CLASS
       NAME "Railroads"
##      STYLE
##        COLOR _white_clr
##        WIDTH 2
##        OUTLINECOLOR _rail_clr
##        OUTLINEWIDTH 1
##      END
       STYLE
         COLOR _rail_clr
         WIDTH 4
##        ANTIALIAS TRUE
       END
       STYLE
         COLOR _white_clr
         WIDTH 2
##        ANTIALIAS TRUE
       END
       STYLE
         SYMBOL 'railway6'
         COLOR _rail_clr
         SIZE 6
       END
     END
   END


[Wed May 13 00:07:29 2009].929243 msDrawMap(): Layer 0 (World), 0.005s
[Wed May 13 00:07:29 2009].931190 msDrawMap(): Layer 2 (CountryZ2), 0.002s
[Wed May 13 00:07:29 2009].932168 msDrawMap(): Layer 4 (Urban Areas Z2), 
0.001s
[Wed May 13 00:07:29 2009].933675 msDrawMap(): Layer 5 (Land Use A), 0.001s
[Wed May 13 00:07:29 2009].933923 msDrawMap(): Layer 6 (Land Use B), 0.000s
[Wed May 13 00:07:29 2009].934913 msDrawMap(): Layer 7 (Province), 0.001s
[Wed May 13 00:07:29 2009].935931 msDrawMap(): Layer 8 (Water p), 0.001s
[Wed May 13 00:07:29 2009].936762 msDrawMap(): Layer 9 (Municipality), 
0.001s
[Wed May 13 00:07:29 2009].936919 msDrawMap(): Layer 10 (Linear Water), 
0.000s
[Wed May 13 00:07:30 2009].773755 msDrawMap(): Layer 12 (RailRoads Z2), 
0.837s
[Wed May 13 00:07:30 2009].866461 msDrawMap(): Layer 16 (tunnels-close), 
0.093s
[Wed May 13 00:07:31 2009].200775 msDrawMap(): Layer 17 (streets-close), 
0.334s
[Wed May 13 00:07:31 2009].309649 msDrawMap(): Layer 18 
(highways-close), 0.109s
[Wed May 13 00:07:31 2009].309785 msDrawMap(): Layer 19 (copyright), 0.000s
[Wed May 13 00:07:31 2009].309810 msDrawLabelCache(): 
labelcache_map_edge_buffer = -10
[Wed May 13 00:07:32 2009].410001 msDrawMap(): Drawing Label Cache, 1.100s
[Wed May 13 00:07:32 2009].410053 msDrawMap() total time: 2.488s
[Wed May 13 00:07:32 2009].589924 msSaveImage() total time: 0.180s
[Wed May 13 00:07:32 2009].590427 mapserv request processing time 
(loadmap not incl.): 2.668s

250K scale:

   SYMBOL
     NAME "railway6"
     TYPE truetype
     FONT arial
     CHARACTER "|"
     GAP -6
   END


   LAYER
     NAME "RailRoads Z1"
     GROUP "rr"
     STATUS DEFAULT
     DATA "NA/RailRds"
     TYPE LINE
     MAXSCALE  500100.0
     MINSCALE   25100.0
     TRANSPARENCY ALPHA
     CLASS
       NAME "Railroads"
       STYLE
         COLOR _dark_gray_clr
         WIDTH 1
##        ANTIALIAS TRUE
       END
       STYLE
         SYMBOL 'railway6'
         COLOR _dark_gray_clr
         SIZE 5
       END
     END
   END


[Wed May 13 00:03:27 2009].45043 msDrawMap(): Layer 0 (World), 0.006s
[Wed May 13 00:03:27 2009].47580 msDrawMap(): Layer 2 (CountryZ2), 0.002s
[Wed May 13 00:03:27 2009].48592 msDrawMap(): Layer 4 (Urban Areas Z2), 
0.001s
[Wed May 13 00:03:27 2009].58275 msDrawMap(): Layer 5 (Land Use A), 0.010s
[Wed May 13 00:03:27 2009].60404 msDrawMap(): Layer 6 (Land Use B), 0.002s
[Wed May 13 00:03:27 2009].61885 msDrawMap(): Layer 7 (Province), 0.001s
[Wed May 13 00:03:27 2009].66543 msDrawMap(): Layer 8 (Water p), 0.005s
[Wed May 13 00:03:27 2009].86803 msDrawMap(): Layer 9 (Municipality), 0.020s
[Wed May 13 00:03:27 2009].87221 msDrawMap(): Layer 10 (Linear Water), 
0.000s
[Wed May 13 00:03:29 2009].919242 msDrawMap(): Layer 11 (RailRoads Z1), 
2.832s
[Wed May 13 00:03:30 2009].357593 msDrawMap(): Layer 14 (highways-far), 
0.438s
[Wed May 13 00:03:30 2009].460126 msDrawMap(): Layer 15 (highways-far), 
0.102s
[Wed May 13 00:03:30 2009].460882 msDrawMap(): Layer 19 (copyright), 0.001s
[Wed May 13 00:03:30 2009].460920 msDrawLabelCache(): 
labelcache_map_edge_buffer = -10
[Wed May 13 00:03:31 2009].372635 msDrawMap(): Drawing Label Cache, 0.912s
[Wed May 13 00:03:31 2009].372693 msDrawMap() total time: 4.336s
[Wed May 13 00:03:31 2009].887170 msSaveImage() total time: 0.514s
[Wed May 13 00:03:31 2009].887664 mapserv request processing time 
(loadmap not incl.): 4.851s