Globe light position

[slaviczavik]

maplibre-gl-js version: v5.0.0-pre.9

browser: Chrome 131.0.6778.140 (arm64)

Steps to Trigger Behavior

1. Set globe projection.
2. Set light property with [1.15, 0, 0] position.
3. Globe is illuminated differently than extruded objects.

Link to Demonstration

See simple example with globe view and city view next to each other with same position.

Expected Behavior

Light position should be same for both views.

Actual Behavior

Looks like light is not correctly positioned for the globe view.

[HarelM]

Globe lighting is the light on "null island".
Extrusion lighting doesn't change from location to location and is somewhat "constant".

[daliborjanak]

From my test, it looks like that light is visible only with sky and the default is really strange for globe:

There is light set to the null island if you set just projection is style:

  "projection": {
    "type": "globe"
  },

but if you add also any sky parameter or only an empty object,

  "projection": {
    "type": "globe"
  },
  "sky": {},

then it turns on the light with a default that makes "night effect" on the visible side. Like this image:

So if you have any sky definition style then it is not usable for the globe. You have to set

  "projection": {
    "type": "globe"
  },
  "sky": {
    "atmosphere-blend": 0
  },

To see the globe without the "night effect". This is IMHO bug

If you set just light, then it doesn't work (another problem):

  "projection": {
    "type": "globe"
  },
  "light":{
    "anchor": "map",
    "color": "white",
    "intensity": 0.4,
    "position": [1.15,210,30], //default
  },

But empty sky with light works and the default is weird

  "projection": {
    "type": "globe"
  },
  "sky":{},
  "light":{
    "anchor": "map",
    "color": "white",
    "intensity": 0.4,
    "position": [1.15,210,30], //default
  },

[HarelM]

In order to see the atmosphere sky is needed to be set. If you add an empty sky object you'll get the sky default values for the sky properties.
Sky uses the light properties to define the atmosphere visibility.
I suggest playing with it a bit to better understand how this works.

[kikuchan]

Hi,
It seems that the axis of rotation of the lighting for globe projection with anchor: 'map' is wrong. (tilted 90 degrees?)

I've successfully got the proper lighting position by using following, a rotation correcting, function:

function lightPosition(lat: number, lng: number) {
  const sin = (d: number) => Math.sin(d * Math.PI / 180);
  const cos = (d: number) => Math.cos(d * Math.PI / 180);
  const acos = (v: number) => Math.acos(v) * 180 / Math.PI;
  const b = acos(cos(lat) * cos(lng));
  const a = acos(sin(lat) / sin(b));
  return [-1, a, b] as [number, number, number];
}

with subsolar point of the Sun:

{
  light: {
    anchor: 'map',
    position: lightPosition(subsolar.lat, subsolar.lng)
  }
}

The result:

I've also created a plugin to overlay a night shadow even on a 2D map, just FYI:
https://github.com/kikuchan/maplibre-gl-nightlayer

Thanks.