Occlusion Culling(遮挡剔除)

Occluder：遮挡者

Occludee：被遮挡者

参考1：https://baijiahao.baidu.com/s?id=1740429096190145270&wfr=spider&for=pc

参考2：https://www.bilibili.com/video/BV1qt411i7sC/

>>EllipsoidalOccluder：椭球的遮挡剔除

判断一个点是否在椭球的背面

var cameraPosition = new Cesium.Cartesian3(5.0, 6.0, 7.0);
var occluderEllipsoid = new Cesium.Ellipsoid(1.0, 1.1, 0.9);
var occluder = new Cesium.EllipsoidalOccluder(occluderEllipsoid, cameraPosition);

 参考：https://blog.csdn.net/u012425087/article/details/132382504