How to use tile textures in a custom layer?

[su-noh]

Tile textures are not accessible from the custom layer, so activating a terrain with the function '.setTerrain()' on the map prevents the custom layer from interacting with the terrain correctly.

To fix this issue, you must be able to obtain the terrain texture from the custom layer and modify the texture of the tile before the terrain is rendered.

I was wondering if there is a way to get the tile texture correctly.

There was a similar discussion here, but I'm adding it because it doesn't match what I'm trying to find out. #2245

[HarelM]

In theory, you have the webgl context, you should be able to query it for what you need, don't you?

[IvanSanchez]

As far as I'm aware, having access to the context gives you access to the bound texture units, but not to any other textures that might be unbound.

[kubapelc]

You could try using the internal function map.terrain.getTerrainData(tileID), see how it is used in painter.ts and see how the returned terrain textures and uniforms are used in the shaders, mainly terrain.vertex.glsl. The source code of get_elevation() function that is used in the shaders is in _prelude.vertex.glsl. You can obtain a list of drawable tileIDs using the internal function map.terrain.sourceCache.getRenderableTiles() (but I'm not entirely sure that is the best function).

[X-plor3r]

It might be related to this.
I've tried to create a custom layer by using internal cache : terrain.sourceCache.getRenderableTiles() and terrain.getTerrainData(tile.tileID)
it seems to return some values but I'm unable to correctly display this layer. there is multiple duplications of the same elevation data in my tiles. I'm not sure what is happening (maybe parent tile / overzoom / ?)

here is the current code: https://jsbin.com/tarevad/edit?html,output

I tried to get some inspiration from here : https://maplibre.org/maplibre-gl-js/docs/examples/globe-custom-tiles/

Anyways, I missing something and any help would be welcome :) I'm not a fluent in shader or math ^^