DWF Viewer and map requests, scale dependent geometry

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DWF Viewer and map requests, scale dependent geometry

Joel Carranza
DWF Viewer and map requests, scale dependent geometry

The MapGuide client as of version 6.5 did a pretty good job in only asking for data when it really needed it. More specifically

- turning a layer off, and then back on, did not result in any server requests. The layer data was cached and reused whenever the layer was turned on

- Zooming in only slightly (perhaps a click of the zoom wheel) did not result in any server requests, unless required by layer scale dependencies

- "Zoom to Previous View" often did not result in an any server requests, if possible
The new DWF viewer does not seem to implement any of this functionality. When I flip a layer off and on, I see in the Apache logs that I am downloading the entire layer over again. When I zoom in a little bit, I am downloading a fresh copy of the entire map! The size and frequency of requests from the DWF viewer may make deployment in the field (over a wireless conection) impossible.

Is this a bug or a feature?
I am guessing that caching is less feasible when you are serving up scale dependent geometry (lines are less detailed the further zoomed out you are), but is there/will there be a way to tune these parameters on a per layer basis? What if I don't want my geometry simplified? Will this have effects on DWF viewer caching?

Joel Carranza
Gatekeeper Systems
626-449-3070 x114

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RE: DWF Viewer and map requests, scale dependent geometry

weltonw
Some notes:
 
1/ There is some potential for optimization here; for example the case where you zoom in slightly.  The server could detect this and not return all the graphics.
 
2/ Keep in mind that the new MapGuide is fundamentally different than the old.  All feature data lives on the server, and thus stylization of that data has to happen on the server.  Also, the client and server need to stay in synch as far as the session state goes.  If you change the view in any way on the client (pan/zoom, toggle a layer's visibility) then this *must* be communicated to the server.  Any optimizations that get performed would be around how the server responds to these updates.
 
3/ DWF Viewer currently does not cache data.  If the need is high enough we could add this support to a future version of the viewer.
 
Walt

        -----Original Message-----
        From: Joel Carranza [mailto:[hidden email]]
        Sent: Wed 3/22/2006 6:30 PM
        To: [hidden email]
        Cc:
        Subject: [mapguide-users] DWF Viewer and map requests, scale dependent geometry
       
       

        The MapGuide client as of version 6.5 did a pretty good job in only asking for data when it really needed it. More specifically

        - turning a layer off, and then back on, did not result in any server requests. The layer data was cached and reused whenever the layer was turned on

        - Zooming in only slightly (perhaps a click of the zoom wheel) did not result in any server requests, unless required by layer scale dependencies

        - "Zoom to Previous View" often did not result in an any server requests, if possible
        The new DWF viewer does not seem to implement any of this functionality. When I flip a layer off and on, I see in the Apache logs that I am downloading the entire layer over again. When I zoom in a little bit, I am downloading a fresh copy of the entire map! The size and frequency of requests from the DWF viewer may make deployment in the field (over a wireless conection) impossible.

        Is this a bug or a feature?
        I am guessing that caching is less feasible when you are serving up scale dependent geometry (lines are less detailed the further zoomed out you are), but is there/will there be a way to tune these parameters on a per layer basis? What if I don't want my geometry simplified? Will this have effects on DWF viewer caching?

        Joel Carranza
        Gatekeeper Systems
        626-449-3070 x114


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