conflict between elevation for MousePosition & terrain layer

[landryb]

Description

If one defines a wms layer to be used for elevation info via MousePosition plugin, then it's also used for terrain via GeoserverBILProvider, while i think it should be enabled for the terrain only if another terrain layer wasnt configured.

I've also witnessed bad crashes (not 100% reproductible) with the following STR:

• enable mouseposition -> client queries the wms layer for bil data
• enabled 3d mode -> either the browser goes OOM, or there's a backtrace in the console log about 'cesium widget' being undefined.. if i can reproduce it will report backtrace.

How to reproduce

configure ms2 with a terrain provider and an addltional layer for elevation/MousePosition:

          "terrainProvider": {
              "type": "cesium",
              "url": "https://3d.craig.fr/terrain",
              "requestVertexNormals": true
          }
...
            "name": "Map",
            "cfg": {
              "additionalLayers": [{
                "type": "wms",
                "url": "https://wms.craig.fr/mnt",
                "visibility": true,
                "title": "Elevation",
                "name": "mnt_raw",
                "format": "image/bil",
                "useForElevation": true,
                "nodata": -9999,
                "littleendian": true,
                "hidden": true
             }],
...
              "name": "MousePosition",
              "cfg": {
                "editCRS": true,
                "showLabels": true,
                "showElevation": true,
                "showToggle": true,
                "filterAllowedCRS": ["EPSG:4326", "EPSG:3857"],
                "additionalCRS": {}
              }

• enable Mouseposition, the WMS server with BIL data is queried for elevation info
• switch to 3d mode, the WMS server with BIL data is still queried/hammered for terrain info

Expected Result

I would expect the cesium terrain provider to be used in priority for the terrain/relief (as its super fast, and optimized/native for cesium), instead of the WMS/BIL layer (which can be very resource consuming)

Current Result

the WMS/BIL server is used for the terrain/relief. The TerrainProvider layer info is fetched (eg there are hits on layer.json) but not used (zero hits on terrain tiles)

Other useful information

two ideas:

• add the WMS elevation layer as GeoserverBILProvider in cesium only if type is ellipsoid (eg the default, no terrain specified there)
• add a new flag (defaulting to true or false) to the additional layer allowing to enable/disable the layer for terrain, and keep/use it only for elevation/mouseposition (eg there's useForElevation, maybe useForTerrain ?)

[landryb]

@tdipisa @allyoucanmap i see that #8323 allows for much improved terrain support, in this context what will happen for the additionalLayers used in the mouseposition plugin ? will we be able to use the additional wms layer only for elevation info (and not terrain) ?

[tdipisa]

@landryb

will we be able to use the additional wms layer only for elevation info (and not terrain) ?

No, we have anyway already defined a new issue for this. I'm going to close this issue in favor of #8579.