Low resolution tiles loading with low VFOV (<=10°) and high pitch

[jo-chemla]

maplibre-gl-js version: 5.18.0

browser: brave latest, chrome latest

Steps to Trigger Behavior

1. Open CSB https://codesandbox.io/p/sandbox/s73fvs
2. It loads esri raster basemap with a pretty high pitch
3. Use buttons to set VFOV to 10° or 40° and notice low resolution tiles loading when high pitch and low VFOV

This might be the kind of bite @HarelM was referring to on PR #4914 (review) exposing Add setVerticalFieldOfView() to public API ?

When using a low VFOV (1-10°), at any pitch larger than 0 - but it becomes more noticeable with the pitch increasing - it seems that the tile selection heuristic wrongly uses lower resolution tiles - for basemaps TMS layers, terrain, etc. See the screencast attached.

2026-02-18.-.09-41-56_8mblocal_7179df13.mp4

Link to Demonstration

MRE CodeSandbox code and preview here https://codesandbox.io/p/sandbox/s73fvs

Expected Behavior

Independent of the pitch / VFOV values, the same resolution TMS tiles should be loaded. Also happens for terrain.

Actual Behavior

Only low resolutions tiles are loaded / higher res are discarded when the camera has a low VFOV and high pitch.

[HarelM]

This is probably related to covering tiles algorithm, which is complicated by itself.
Feel free to investigate what can solve this.

[jo-chemla]

Thanks for getting back. This was actually already exposed sometime ago in #2444 and #4940 (2023-04 and 2024-10) and theoretically fixed in #4779
Do you think there might have been a rollback of the suggested fix with v5 tile loading strategy being updated?

[HarelM]

The relevant fix introduced render tests, these are usually kept without changes to make sure old bugs do not resurface.
It might be that the fix did not cover all use cases.
Cc: @NathanMOlson