QuantizedMesh: skip loading low resolution tiles when camera initialised close to mesh

[Ylannl]

Description

I'm working on a project that uses the WMTS and GeoJSON overlays on a quantised mesh. This works well, except for the initialisation phase in case the camera is initialised close to the terrain:

https://github.com/user-attachments/assets/456ed008-e730-4f2c-8e66-7040da3bf0b8

It takes quite long to load all the tiles all the way up to the desired state for the current camera postion (with the exception of the 3D Tiles with building models). This is especially the case with a slow connection/slow server, eg. I was able to improve this situation somewhat by moving the quantised mesh to a more responsive server. However, it is still very noticeable, seeing the low resolution tiles gradually being replaced by the higher resolution ones. It is also noticeable when you zoom in very fast (eg. from globe level to city level).

Solution

I get the impression that it always starts loading from the root (coarsest/lowest resolution tile) and then gradually refines without skipping any tree levels. Maybe even also for the overlays? Is this correct? And is there a way skip those intermediate levels with the existing codebase and immediately load the high resolutions tiles? If not, I think this would be a nice optimisation to implement. It would give the user a more responsive experience + save bandwidth. Do you agree? If yes, how could this implemented best? I'm willing to contribute code.

Alternatives

Moving all the tile sources to faster servers, using CDN etc? This will, however, not tackle the root cause of the problem, only make it less noticeable.

Additional context

No response

[gkjohnson]

Hi @Ylannl! Yes currently the tiles renderer loads all tiles from the root of the tile set down to the target ones. This has become more noticeable specifically as tile overlays are added and servers become slow to respond. I've been thinking this through for a bit now and looking at how Cesium is handling it and will hopefully be able to work on this in the coming months. Handling this correctly and adjusting the traversal algorithm is not so straight forward. Hopefully we'll be able to avoid things like sudden pops and gaps in tile geometry loading but we'll see.