Blurred map when using terrain / Strange Tile LOD resolution

[kaij]

Display of terrain texture is blurry (see picture top left corner) or contains low resolution (see video). It seems like the wrong resolution is being displayed. It is not related to loading speed, but to the strategy how

Currently, I have no idea where to look in the code. Maybe any of you have an idea what I could check or what could trigger this behaviour? Could it maybe also be related to the terrain / satellite texture provider (maptiler)?

maplibre-gl-js version: 5.0.0
browser: Chrome

Steps to Trigger Behavior

1. Create map with terrain
2. move camera by dragging or programmatically

Link to Demonstration

See video and image.

terrain-load.mov

Expected Behavior

Map with evenly distributed tile resolutions and satellite map, no tiling effect on the texture.

Actual Behavior

As can be seen in the image and video, there is a tiling effect on the texture and in the video top left, a mountain that is ~500m behind is completely blurred out.

[HarelM]

There is a very long discussion around tile loading in this PR:

• Fix level of detail at high pitch #4779

I think the current behavior is better than what it used to be.
I think you might be able to override the strategy as part of the source definition, but I'm not sure this was thoroughly tested, so you'll need to dig into this your own.

The behavior I see in the video seems reasonable to me (I might be missing something obvious), so I'll be converting this issue to a discussion.
If you think there's an issue here that needs to be fixed, please provide a minimal reproduction as was requested in the temple and better explain the issue.
The following style.json can help seeing the different tiles that are loaded according to the relevant zoom level:
https://github.com/maplibre/demotiles/blob/gh-pages/debug-tiles/style.json

[kaij]

Thanks for the quick response and this background information! In #4779 it states "... it is assumed that all tiles are at the same elevation as the center point. ...". This would very likely be the reason for the massive blur in the high up mountains. I agree this is something I should look into and see if it can be improved with a custom strategy. I guess also by allowing pitch values >90deg the problem should be seen increasingly.

[kubapelc]

The tiling you see in the video is mostly in your satellite data. Also since terrain will draw near tiles at a higher zoom level, it seems like the satellite map you use has a slightly different color tint on each zoom level.

If you want to play around with how tile lod or zoom level is determined, I think the relevant function is calculateTileZoom in covering_tiles.ts. I think it should affect terrain as well, but I'm not entirely sure.

[kaij]

Thanks @kubapelc! I'll get a look at this function.