EntityClustering crashes when DataSource is removed

[vividos]

I'm using some parts of code from the Clustering Sandcastle demo. In my application I have several DataSources (one CustomDataSource, and potentially some CzmlDataSources). I'd like to cluster the elements in the data sources (mostly pins, but also points and labels) and I'm creating one Cesium.EntityCluster object:

https://github.com/vividos/WhereToFly/blob/5cb867c4c9e89e7c6ab0660f5dcd2b13f05b0a45/src/App/Resources/Assets/map/mapView3D.js#L390

I'm setting the EntityCluster object for my CustomDataSource:
https://github.com/vividos/WhereToFly/blob/5cb867c4c9e89e7c6ab0660f5dcd2b13f05b0a45/src/App/Resources/Assets/map/mapView3D.js#L265

Now when adding CZML files to my map view, I'm also setting the clustering property of the just loaded CzmlDataSource:
https://github.com/vividos/WhereToFly/blob/5cb867c4c9e89e7c6ab0660f5dcd2b13f05b0a45/src/App/Resources/Assets/map/mapView3D.js#L963

Clustering works well, and I can even switch it on/off globally.

Now the map view crashes and stops rendering when I remove a CZML data source again:
https://github.com/vividos/WhereToFly/blob/5cb867c4c9e89e7c6ab0660f5dcd2b13f05b0a45/src/App/Resources/Assets/map/mapView3D.js#L1125

As soon as the scene is re-rendered, the following call stack is shown (CesiumUnminified is used here):

An error occurred while rendering. Rendering has stopped.
TypeError: Unable to get property '_textureAtlas' of undefined or null reference
TypeError: Unable to get property '_textureAtlas' of undefined or null reference
   at Billboard.prototype.setImage (.../Cesium/Cesium.js:158459:5)
   at image.set (.../Cesium/Cesium.js:158149:11)
   at BillboardVisualizer.prototype.update (.../Cesium/Cesium.js:93141:9)
   at DataSourceDisplay.prototype.update (.../Cesium/Cesium.js:204161:9)
   at Viewer.prototype._onTick (.../Cesium/Cesium.js:300870:5)
   at Event.prototype.raiseEvent (.../Cesium/Cesium.js:14081:9)
   at Clock.prototype.tick (.../Cesium/Cesium.js:50418:5)
   at CesiumWidget.prototype.render (.../Cesium/Cesium.js:294541:7)
   at render (.../Cesium/Cesium.js:293797:13)

(I shortened the paths a bit).

I also tried setting the clustering property to undefined or to a newly created Cesium.EntityCluster object, but the crash stays the same.

I even tried to "force a re-cluster", just like shown in the sandcastle demo, setting pixelRange to 0 and back to the last value.

From the documentation I got the idea that sharing EntityCluster objects is possible, but maybe I'm just doing something wrong. Thanks for helping in advance!

Browser: This occurs in the UWP WebView (I think it's based on Edge, but I'm not sure), and in the Android WebView, which uses the installed Chrome.

Operating System: Windows 10 / Android 11

[vividos]

I debugged my case here today, and I think that sharing EntityCluster objects is currently not supported by DataSource objects. The reason for this is this line:

cesium/Source/DataSources/DataSourceDisplay.js

Lines 454 to 455 in b333448

	var entityCluster = dataSource.clustering;
	primitives.remove(entityCluster);

Here, the EntityCluster is removed from the PrimitiveCollection when the DataSource is removed from the DataSourceCollection in the viewer. Since the PrimitiveCollection destroys all primitives, the EntityCluster is also destroyed. In the next render loop, the EntityCluster is accessed by other DataSource objects, which is destroyed now.

My workaround for this is to make my only EntityCluster instance un-destroyable (by setting a new empty destroy() function). That seems to work.

The fix would be to give the EntityCluster object some sort of sharedInstance property and when true, not remove it from the primitives collection (or don't add it in the first place, but give it a distinct Display object that takes care of rendering).

Alternatively the documentation should be changed to clarify that EntityCluster object indeed can't be shared among data sources, but that would prevent clustering from working across data sources. The documentation can be found here:

cesium/Source/DataSources/DataSource.js

Line 84 in b333448

* Gets or sets the clustering options for this data source. This object can be shared between multiple data sources.

[srothst1]

@vividos Thank you for submitting such a detailed issue. I am currently implementing a solution. To ensure that my solution solves the correct bug, it would be helpful if you provided a sandcastle demo that outlines the specific problem. Let me know if this is possible.

[vividos]

Here's a Sandcastle that shows the error; I thought the bug was triggered only by clicking on the "Remove data source A" button, but it crashes immediately after init, since there's no way to let the data source know that the EntityCluster object is shared.

https://sandcastle.cesium.com/#c=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

[srothst1]

@vividos Thanks for sharing the sandcastle demo with me - there are clearly a few issues here. It seems like updating entityCluster may not be sufficient to solve the entire problem.