On Nov 30, 2:27 pm, Chad Killingsworth
<chadkillingswo...@missouristate.edu> wrote:
> I put 3 tile layers on a map each as their own OverlayView. I also put
> the same 3 tile layers on a map in the same OverlayView. On an iPhone,
> there is a pretty significant performance difference between a single
> layer and 3 layers. However there was not a noticeable difference
> between 3 layers in a single OverlayView or in multiple OverlayViews.
The tile latency will mask the extra CPU usage, but, why compute
identical tile offsets in different OverlayViews ?
> This may be due to the fact that I throttle the bounds_changed event
> to only fire once a second.
Try using an "idle" event listener without timer interrupts.
> This leads me to believe that the vast
> majority of the performance degradation with multiple layers comes
> from the rendering and memory usage of that many DOMNodes and images
> rather than from the events.
The primary delay is the limited iPhone bandwidth.
> Of course at much higher numbers of
> layers there may indeed be a significant difference, however this
> seems to be a pretty specialized optimization.
>
> If I needed to display large numbers of tile layers simultaneously, I
> personally would pursue a server side solution rather than having the
> client render that many layers. Of course not everyone may have that
> option.
The tile sets may originate from different servers like:
www.polyarc.us/sparse
Even Google's own "HYBRID" tiles are split across hosts.
> Using my class, the performance of the map with 3 layers is
> acceptable. Beyond that, your mileage may vary.
A general solution ought to support Internet Explorer 6. It ought to
compensate for getBounds errors at low numbered zoom levels. It ought
to calculate tile offsets correctly for maps spanning the
International Date Line. The use of a timer interrupt just adds extra
overhead.
Peter,
Please provide a link, either V2 or V3, to what you are trying to do.
You ought to be able to build a proper URL for your server from the
examples.
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