Add support for clamping Vector 3D Tile point features to Terrain or 3d Tiles

[gdiehlEB]

Fixes Issue #11544

Adds the global heightReference member as an option for Cesium3DTileset to support clamping Billboards and Labels of Vector 3D Tiles point features to Terrain or 3D Tiles.

TO-DO:

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have update the inline documentation, and included code examples where relevant
• Review and revise inline documentation
• I have performed a self-review of my code

[gdiehlEB]

@ggetz when you have time can you provide some feedback for this implementation? Thanks again for all of your help.

[ggetz]

Thanks @gdiehlEB, we'll do so shortly!

[ggetz]

@gdiehlEB Before we can review the code here, you'll need to have Contributor License Agreement covering you or the organization you are contributing on behalf of. Please ask EB to submit one and that you are listed on it.

[gdiehlEB]

@gdiehlEB Before we can review the code here, you'll need to have Contributor License Agreement covering you or the organization you are contributing on behalf of. Please ask EB to submit one and that you are listed on it.

@ggetz the corporate CLA has been submitted.

[ggetz]

Thanks @gdiehlEB!

We can test this out more properly once #11604 has been merged into main.

In the meantime, I don't think it's ideal to pass in scene from the top-level of Cesium3DTileset. I wonder if there is a way we can pass that in at a lower level instead.

[gdiehlEB]

Thanks for the feedback @ggetz! I had the same thought and have been looking for an alternative to passing the scene in, but I couldn’t find anywhere that the viewer instance was already available to access. If the heightReference is just set when creating the Cesium3DTileset instance similar to classificationType that seemed like the place to pass in the scene ie:

const tileset = await Cesium.Cesium3DTileset.fromUrl('/Apps/SampleData/lineworks/vector-tile.json', {
//clamp polylines
  classificationType: Cesium.ClassificationType.TERRAIN,
//clamp point features
  heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
//not ideal
  scene: viewer.scene
});

There may be another way that I am missing though. I saw that in the clamping sandcastle the Entity API is used and provides access to the viewer so no clues there.