Turn off skyAtmosphere after sunset?

CesiumJS
1

I’m using Cesium for out-the-window visualization in a flight simulator. I’d like to hide/destroy the skyAtmosphere at night.

Any suggestions on how to determine if the sun has set?

Thanks, Matt.

2

We actually had some code laying around to do something close to this. Here’s a Sandcastle example that uses the camera position to determine whether the sun is visible at that location and turns on/off atmosphere. Just replace viewer.scene.camera.position with whatever position you want. Eventually, we’ll probably have some cool built in visualization for this in Cesium itself.

var viewer = new Cesium.Viewer(‘cesiumContainer’);

var transformMatrix = new Cesium.Matrix4();

var toSun = new Cesium.Cartesian3();

var toMoon = new Cesium.Cartesian3();

viewer.clock.onTick.addEventListener(function(clock) {

var position = viewer.scene.camera.position;

var up = viewer.scene.globe.ellipsoid.geodeticSurfaceNormal(position);

var time = clock.currentTime;

Cesium.Transforms.computeTemeToPseudoFixedMatrix(time, transformMatrix);

Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(time, toSun);

Cesium.Matrix3.multiplyByVector(transformMatrix, toSun, toSun);

Cesium.Cartesian3.normalize(toSun, toSun);

viewer.scene.skyAtmosphere.show = Cesium.Cartesian3.dot(up, toSun) > 0.0;

});

3

Thanks!

I also found a nice little library for calculating the sun position:

https://github.com/mourner/suncalc

my code:

function updateSkyAtmosphere() {

var dateNow = Cesium.JulianDate.toDate(viewer.clock.currentTime);

var sunPos = SunCalc.getPosition(dateNow, acState.lat, acState.lng);

viewer.scene.skyAtmosphere.show = sunPos.altitude > 0;

}

4

I just tested this out yesterday and it worked great! I was trying to hack around in non-native ways, but this ended up being great.

However, i do think it’d be great to have a dynamic SkyAtmosphere property to change with sun altitude, similar to how you can do this for Atmosphere with scene.atmosphere.dynamicLighting = DynamicAtmosphereLightingType.SUNLIGHT;

I believe you guys already have something in place for Cesium Unreal, but it could be valuable for JS