Tile height artifacts in sandcastle with Google 3D Photorealistic Tiles

[arobison]

What happened?

While exploring the Google tileset example in sandcastle, I noticed a rendering artifact where tiles would occasionally change the height at which they were rendered, creating a visual discontinuity:

The tiles that are at the incorrect height appear to be tied to camera position; moving the camera will change which tiles are popped up to the incorrect height.

Reproduction steps

1. Navigate to https://sandcastle.cesium.com/?id=google-photorealistic-3d-tiles
2. Wait for the tiles to begin streaming in
3. Manually click to move the camera to the Long Beach shipping yard (33.71657, -118.24779)
4. Drag the camera around and observe the tiles popping up and down
   ...

Sandcastle example

https://sandcastle.cesium.com/?id=google-photorealistic-3d-tiles

Environment

Browser: Microsoft Edge
CesiumJS Version: 1.139.1
Operating System: Windows 11

[ggetz]

Thanks @arobison! I'm curious if this is a data issue or a bug in CesiumJS itself. I would recommend trying to reproduce in another runtime like Cesium for Unreal and seeing if we see the same thing.

[j9liu]

@arobison @ggetz I'm also seeing this in Cesium for Unreal:

We've seen something similar in the past in Google Photorealistic 3D Tiles where tiles at different LODs were not at the same height as each other. However, that happened due to an update to the data itself, not with any renderer changes.

[arobison]

@LisaBosCesium @dkbraig do we have contacts at Google to ask about this?