I want to know how to judge the point on the back of the sphere.

1. A concise explanation of the problem you're experiencing.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

4. The Cesium version you're using, your operating system and browser.

Not very good at English, all rely on google, thank you for your help

var projectedPoint = new Cesium.Cartesian3.fromDegrees(lon, lat, 0);
    var trans = Cesium.SceneTransforms.wgs84ToWindowCoordinates(mapApp.cesMap.scene_, projectedPoint);
    var ray = mapApp.cesMap.camera_.cam_.getPickRay(trans);
    var position = mapApp.cesMap.globe_.pick(ray, mapApp.cesMap.scene_);
    if (Cesium.defined(position)) {
        var cartographic = Cesium.Ellipsoid.WGS84.cartesianToCartographic(position);
        var lat2 = Cesium.Math.toDegrees(cartographic.latitude);
        var lon2 = Cesium.Math.toDegrees(cartographic.longitude);
//juge lat , lat2 lon,lon2
//low efficiency!!!!!!!!!

Can you explain more what you’re trying to do? What kind of application are you working on?