[OpenLayers-Dev] Re: vector layer with highest zIndex not overlaying other vector layers

[Andreas Hocevar]

Hi,

from what you describe, your use case screams for rendering features on the server and maintaining only a layer of selected features (using the GetFeature control) on the client. For this, however, you would need a WMS or something similar that can render your features on the server.

You may want to have a look at http://ol-performance.appspot.com/, especially the "Combine OGC Services Wisely" section which shows alternative ways of feature selection.

Also, don't expect too much performance improvements from the Cluster strategy. It will speed up rendering and panning for sure, but the real bottleneck is parsing the features as they arrive from the server. The cluster strategy is a great way to improve the perception of otherwise overcrowded maps, but it is not an all-purpose cure for performance issues.

Regards,
Andreas.

On Oct 3, 2010, at 15:57 , crb wrote:

> 
> Hi Andreas.  Thanks for the reply (and for the reply to my other post of the
> same day).
> 
> The reason for the extra layer for the selected features is because we want
> to show selected features at all scales, but the vector layer for our
> "locations" layer has too many features to display at all scales:  it drags
> IE to a crawl, rendering it unusable.  So for our "main", location features
> layer, we display only at the 10th zoom level and we display only the
> features within the maps current extent (requiring a callback to the server
> every time the extent changes) and we use a cluster strategy for it.  This
> helps with the locations layer (sort of -- I'll be posting again shortly in
> another thread regarding problems we're having with the cluster strategy)
> but so that the user can always see all the features that they've selected,
> we need a 2nd vector layer (or equivalent) to display only selected features
> at all scales.
> 
> Even given that, we've decided to hold off adding a 2nd selected features
> layer for to make sure we can get the cluster strategy working the way we
> need it first.  We'll likely revisit this, but we have to resolve our other
> issue first...
> -- 
> View this message in context: http://osgeo-org.1803224.n2.nabble.com/vector-layer-with-highest-zIndex-not-overlaying-other-vector-layers-tp5592538p5596175.html
> Sent from the OpenLayers Dev mailing list archive at Nabble.com.
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-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.