Improve Cesium Viewer performance when clamping to 3d Tiles with HeightReference.CLAMP_TO_3D_TILE

[gdiehlEB]

Feature

Current state:
Clamping billboards & labels to a 3d tile with HeightReference.CLAMP_TO_3D_TILE drops the FPS of the cesium viewer when zooming / moving the camera. Above a certain number of points the FPS drops to 0 (viewer freezes), and the presence of labels lowers the threshold for this. This does not happen when clamping to terrain with HeightReference.CLAMP_TO_TERRAIN.

Feature Request: If possible, support clamping a larger number of billboards & labels to 3d tiles without noticeable performance impact in the Cesium viewer.

[ggetz]

Thanks for opening this request @gdiehlEB! Would you be able to give us the a rough number of billboards and labels you're typically dealing with?

[jilliandonnae]

Just to update this issue with info discussed in Slack:

• @gdiehlEB shared a typical use case site (customer site so it was shared privately)
• Linework layer appears to have 332 billboards, 83 of these with label

[ggetz]

Also reported with clamping models to Google's 3D Tiles in #12055