Clamped billboard has incorrect bounding sphere in 2D and Columbus View

[hpinkos]

https://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Clamp%20to%20Terrain.html

• Switch to 2D or CV
• Double click the label to track it

The selection indicator is in the wrong place and the camera seems to be tracking wherever the selection indicator is pointing to

[hpinkos]

This also don't work for a clamped model. In fact, if you switch to the model demo in that ground clamping example you get crazy flickering between Mt Saint Helens and somewhere in Mexico

[rahwang]

Came up again in the forum here: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/z4o1l7bKtZs

[mramato]

This may actually be fixed by #5136 (still open). Someone should test out that branch for this issue.

[pjcozzi]

@rahwang we recently merged #5136 into master. Can you please test if this issue is fixed?

Try the hosted version from CI: http://cesium-dev.s3-website-us-east-1.amazonaws.com/cesium/master/

[rahwang]

Trying to access Sandcastle on the hosted version gives me a 404 for some reason, but I tried it locally and it doesn't look like the problem is fixed on master -- same behavior as before.

[hpinkos]

The problem has something to do with billboards with HeightReference.CLAMP_TO_GROUND. (Point entities use a billboard behind the scenes when the height reference option is used)
The bounding sphere in 2D/CV is way wrong.

Without CLAMP_TO_GROUND :

With CLAMP_TO_GROUND:

var viewer = new Cesium.Viewer('cesiumContainer');
var scene = viewer.scene;
var cesiumTerrainProviderMeshes = new Cesium.CesiumTerrainProvider({
    url : 'https://assets.agi.com/stk-terrain/v1/tilesets/world/tiles',
    requestWaterMask : true,
    requestVertexNormals : true
});
viewer.terrainProvider = cesiumTerrainProviderMeshes;
viewer.scene.globe.depthTestAgainstTerrain = true;

var billboards = scene.primitives.add(new Cesium.BillboardCollection({
    scene: scene 
}));
billboards.add({
    image : '../images/facility.gif',
    position : Cesium.Cartesian3.fromDegrees(-122.1958, 46.1915),
    heightReference : Cesium.HeightReference.CLAMP_TO_GROUND
});
billboards.debugShowBoundingVolume = true;

@bagnell any ideas?

[thw0rted]

Hello from the future! I am also suffering from this issue -- as a result, I can either clamp billboards, or use a terrain provider, but never both.

Is there any update on the problem? My first thought was to just "clamp" them myself using Scene#clampToHeightMostDetailed at billboard creation time, but the docs say it will throw if called in 2D mode.

[hpinkos]

Sorry @thw0rted, no I don't have an update. Instead of clamping, you can try using sampleTerrainMostDetailed to get a position for the billboard with the height of terrain.

[thw0rted]

I'm working up something like this now. Because of the way I work with data, it's going to be simpler to make Entities, then "fix" their height, rather than correcting the data before creating Entities. I'll let you know how it goes, but just fixing the CLAMP behavior in 2D would certainly simplify things...

[thw0rted]

Tentatively optimistic -- I think my implementation works, though right now I'm only dealing with those that have a ConstantPositionProperty. (I found out the hard way, ConstantPositionProperty#getValue throws without a time argument, even though it is ignored when the property is in a fixed reference frame...)

[chdenat]

Hello the earth, we're near 2025...

The only way I found to avoid floating point when you change from a scene mode to another is to change the billboard attribute heightReference (So you need to redraw all your Point entities)

Here, noRelief = no terrain or terrain is ellipsoid (flat)

heightReference: noRelief?Cesium.HeightReference.NONE:Cesium.HeightReference.CLAMP_TO_GROUND

So I think that changing the Cesium code somewhere, to avoid clamping to ground when there is no relief should be easy to do.