一、什么是实体

官网解释

• Entity instances aggregate multiple forms of visualization into a single high-level object. They can be created manually and added to Viewer#entities or be produced by data sources, such as CzmlDataSource and GeoJsonDataSource.
• 实体实例将多种形式的可视化聚合到单个高级对象中。它们可以手动创建并添加到 Viewer#实体中，也可以由数据源(如CzmlDataSource和GeoJsonDataSource)生成。
• 我的理解就是一个实例化出来的物体对象，它可以是多边形，可以是立方体，也可以是模型。

二、创建实体并添加到场景

（一）创建场景

• 这个在前面系列中已经讲过了，很简单

（二）创建实体并添加到场景

• 可以先创建再添加

• 也可以直接创建+添加

  // 单点
  viewer.entities.add({
  position : Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883),
  point : {
  pixelSize : 10,
  color : Cesium.Color.YELLOW
  }
  });

  // polyline - 线
  viewer.entities.add({
  name: 'Red line on the surface',
  polyline: {
  positions: Cesium.Cartesian3.fromDegreesArray([
  75, 35,
  125, 35
  ]),
  width: 5,
  material: Cesium.Color.RED
  }
  });

  // polylineVolume - 折线
  function computeCircle(radius) {
  var positions = [];
  for (var i = 0; i < 360; i++) {
  var radians = Cesium.Math.toRadians(i);
  positions.push(new Cesium.Cartesian2(radius * Math.cos(radians), radius * Math.sin(radians)));
  }
  return positions;
  }
  viewer.entities.add({
  name: 'Red tube with rounded corners',
  polylineVolume: {
  positions: Cesium.Cartesian3.fromDegreesArray([
  85.0, 32.0,
  85.0, 36.0,
  89.0, 36.0
  ]),
  shape: computeCircle(60000.0),
  material: Cesium.Color.RED
  }
  });

  // Polygon - 面
  viewer.entities.add({
  name: 'Red polygon on surface',
  polygon: {
  hierarchy: Cesium.Cartesian3.fromDegreesArray([
  115.0, 37.0,
  115.0, 32.0,
  107.0, 33.0,
  102.0, 31.0,
  102.0, 35.0
  ]),
  material: Cesium.Color.RED
  }
  });

  // Circle - 圆
  viewer.entities.add({
  position: Cesium.Cartesian3.fromDegrees(111.0, 40.0, 150000.0),
  name: 'Green circle at height',
  ellipse: {
  semiMinorAxis: 300000.0,
  semiMajorAxis: 300000.0,
  height: 200000.0,
  material: Cesium.Color.GREEN, // 单色
  // material: Cesium.Color.RED.withAlpha(0.5), // 透明色
  // material: "./sampledata/images/globe.jpg", // 图片
  fill: true,
  outline: true, // 必须设置height，否则ouline无法显示
  outlineColor: Cesium.Color.BLUE.withAlpha(0.5),
  outlineWidth: 10.0 // 不能设置，固定为1
  }
  });

  // box - 盒子
  viewer.entities.add({
  name: 'Blue box',
  position: Cesium.Cartesian3.fromDegrees(homePOsition[0], homePOsition[1], 0),
  box: {
  dimensions: new Cesium.Cartesian3(400000.0, 300000.0, 500000.0),
  material: Cesium.Color.BLUE
  }
  });

  // Ellipse - 椭圆
  viewer.entities.add({
  position: Cesium.Cartesian3.fromDegrees(103.0, 40.0),
  name: 'Red ellipse on surface with outline',
  ellipse: {
  semiMinorAxis: 250000.0,
  semiMajorAxis: 400000.0,
  material: Cesium.Color.RED.withAlpha(0.5),
  outline: true,
  outlineColor: Cesium.Color.RED
  }
  });

  // Corridor - 走廊
  viewer.entities.add({
  name: 'Red corridor on surface with rounded corners and outline',
  corridor: {
  positions: Cesium.Cartesian3.fromDegreesArray([
  100.0, 40.0,
  105.0, 40.0,
  105.0, 35.0
  ]),
  width: 200000.0,
  material: Cesium.Color.RED.withAlpha(0.5),
  outline: true,
  outlineColor: Cesium.Color.RED
  }
  });

  // Cylinder - 圆柱
  viewer.entities.add({
  name: 'Green cylinder with black outline',
  position: Cesium.Cartesian3.fromDegrees(100.0, 40.0, 200000.0),
  cylinder: {
  length: 400000.0,
  topRadius: 200000.0,
  bottomRadius: 200000.0,
  material: Cesium.Color.GREEN.withAlpha(0.5),
  outline: true,
  outlineColor: Cesium.Color.DARK_GREEN
  }
  });

  // Cone - 圆锥
  viewer.entities.add({
  name: 'Red cone',
  position: Cesium.Cartesian3.fromDegrees(105.0, 40.0, 200000.0),
  cylinder: {
  length: 400000.0,
  topRadius: 0.0,
  bottomRadius: 200000.0,
  material: Cesium.Color.RED
  }
  });

  // rectangle - 矩形
  viewer.entities.add({
  name: 'Red translucent rectangle with outline',
  rectangle: {
  coordinates: Cesium.Rectangle.fromDegrees(80.0, 20.0, 110.0, 25.0),
  material: Cesium.Color.RED.withAlpha(0.5),
  outline: true,
  outlineColor: Cesium.Color.RED
  }
  });

  // Sphere - 球体
  viewer.entities.add({
  name: 'Red sphere with black outline',
  position: Cesium.Cartesian3.fromDegrees(107.0, 40.0, 300000.0),
  ellipsoid: {
  radii: new Cesium.Cartesian3(300000.0, 300000.0, 300000.0),
  material: Cesium.Color.RED.withAlpha(0.5),
  outline: true,
  outlineColor: Cesium.Color.BLACK
  }
  });

  // ellipsoid - 椭球体
  viewer.entities.add({
  name: 'Blue ellipsoid',
  position: Cesium.Cartesian3.fromDegrees(114.0, 40.0, 300000.0),
  ellipsoid: {
  radii: new Cesium.Cartesian3(200000.0, 200000.0, 300000.0),
  material: Cesium.Color.BLUE
  }
  });

  // wall - 墙
  viewer.entities.add({
  name: 'Green wall from surface with outline',
  wall: {
  positions: Cesium.Cartesian3.fromDegreesArrayHeights([
  107.0, 43.0, 100000.0,
  97.0, 43.0, 100000.0,
  97.0, 40.0, 100000.0,
  107.0, 40.0, 100000.0,
  107.0, 43.0, 100000.0
  ]),
  material: Cesium.Color.GREEN
  }
  });

这一段代码参考来源