topic Re: Rendering flickers when using Cluster in ArcGIS API for Silverlight Questions

Rendering flickers when using Cluster

BjørnarSundsbø — Sun, 23 Jan 2011 16:03:17 GMT

I tried creating a custom clusterer (derived from GraphicsClusterer) to do the same as the FlareClusterer but without the flare effect. I then noticed that when I change the geometry of Graphics (realtime update from server where the Graphic geometry changes). Whenever this happens, all the Graphic objects on the screen flickers. The FlareClusterer gives the same effect. When removing any clusterer from the layer the rendering is smooth.

I can't use clustering if it causes this kind of flickering. Is this the way clusterers works, or is there some inefficiencies in the clusterer that causes this? There are less than 15 graphics in all the layers being displayed, so this should not really cause poor performance.

It appears as if the whole layer is cleared when clustering is reapplied after a change of geometry, and then redrawn, instead of only the features that have been affected by the change. I would think that would leave an even better performance perception. And/or when clustering is enabled, draw to a backbuffer in an ascync call, and then replace the entire content of the layer.

Clustering as it is does not not perform well in a dynamic context. Are there any workarounds for this, or plans for improving this feature?

I use the latest release (2.1).

Re: Rendering flickers when using Cluster

dotMorten_esri — Mon, 24 Jan 2011 15:53:05 GMT

If you change the geometry, the clusters needs to be recalculated and rerendered. This is per design.

Re: Rendering flickers when using Cluster

BjørnarSundsbø — Mon, 24 Jan 2011 18:26:10 GMT

I assumed so, but do you plan to do anything about the flickering.

Re: Rendering flickers when using Cluster

dotMorten_esri — Mon, 24 Jan 2011 23:46:58 GMT

Because the entire cluster set gets invalidated, the clusters needs to be completely re-rendered. This will cause a quick flicker. If you have data that frequently update, I suggest you don't use clustering (especially considering you said you only have 15 points)

Re: Rendering flickers when using Cluster

BjørnarSundsbø — Tue, 25 Jan 2011 06:09:53 GMT

I have quite a few more features than 15. Just wanted to illustrate I got the flickering even with so few features. There will be frequent updates (every 5 - 45 second per feature). Clustering has been disabled because of the flickering.

Re: Rendering flickers when using Cluster

BjørnarSundsbø — Thu, 01 Dec 2011 12:17:54 GMT

Because of the number of items and refresh frequency of a layer, the flickering when a geometry changes is not acceptable for our users, and is considered a bug.

Is this an issue you can put on your todo-list? I tried to report it in the version 2.2 beta program, but it was not followed up.

Re: Rendering flickers when using Cluster

DavidPilcher — Thu, 26 Jun 2014 02:36:38 GMT

It appears this problem still exists. Is it not possible to redraw without flickering?