【Cesium入门教程】第七课：Primitive图元

Cesium丰富的空间数据可视化API分为两部分：primitive API面向三维图形开发者，更底层一些。

Entity API是数据驱动更高级一些。

// entity
// 调用方便，封装完美
// 是基于primitive的封装// primitive
// 更接近底层
// 可以绘制高级图形
// 由Geometry(几何形状)、(Appearance)外观组成

const primitive = new Cesium.Primitive({geometryInstances: new Cesium.GeometryInstance({geometry: new Cesium.EllipseGeometry({center: Cesium.Cartesian3.fromDegrees(-100.0, 20.0),semiMinorAxis: 500000.0,semiMajorAxis: 1000000.0,rotation: Cesium.Math.PI_OVER_FOUR,vertexFormat: Cesium.VertexFormat.POSITION_AND_ST}),}),appearance: new Cesium.EllipsoidSurfaceAppearance({material: Cesium.Material.fromType('Stripe')})
})
viewer.scene.primitives.add(primitive);

组合图形

<h1 id="m7WFT">组合图形</h1>
```javascript
const rectangleInstance = new Cesium.GeometryInstance({geometry: new Cesium.RectangleGeometry({rectangle: Cesium.Rectangle.fromDegrees(-140.0, 30.0, -100.0, 40.0),vertexFormat: Cesium.PerInstanceColorAppearance.VERTEX_FORMAT}),id: 'rectangle',attributes: {color: new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5)}
});const ellipsoidInstance = new Cesium.GeometryInstance({geometry: new Cesium.EllipsoidGeometry({radii: new Cesium.Cartesian3(500000.0, 500000.0, 1000000.0),vertexFormat: Cesium.VertexFormat.POSITION_AND_NORMAL}),modelMatrix: Cesium.Matrix4.multiplyByTranslation(Cesium.Transforms.eastNorthUpToFixedFrame(Cesium.Cartesian3.fromDegrees(-95.59777, 40.03883)), new Cesium.Cartesian3(0.0, 0.0, 500000.0), new Cesium.Matrix4()),id: 'ellipsoid',attributes: {color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.AQUA)}
});viewer.scene.primitives.add(new Cesium.Primitive({geometryInstances: [rectangleInstance, ellipsoidInstance],appearance: new Cesium.PerInstanceColorAppearance()
}));

点击事件

<h1 id="qr6o4">点击事件：</h1>
<h3 id="XXD1c">添加地形图层后去画点</h3>
```javascript
let viewer = new Cesium.Viewer('cesiumContainer', {terrainProvider: Cesium.createWorldTerrain()
})let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction((event) => {//返回一个笛卡尔坐标let position = viewer.scene.pickPosition(event.position);//如果有这个坐标if (Cesium.defined(position)) {console.log(position)viewer.entities.add({position: position,point: {color: Cesium.Color.BLUE,pixelSize: 20,},})console.log(viewer.entities)}
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

事件注销

handler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_CLICK)//移除左键点击事件

申明变量

let pickModel

鼠标移动事件

//添加建筑物
const city = viewer.scene.primitives.add(new Cesium.Cesium3DTileset({url: Cesium.IonResource.fromAssetId(75343),})
);
viewer.flyTo(city)let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction((event) => {//拾取模型const pick = viewer.scene.pick(event.endPosition);if (pick) {if (pickModel) {pickModel.color = Cesium.Color.WHITE;}pick.color = Cesium.Color.ORANGERED;pickModel = pick;}
}, Cesium.ScreenSpaceEventType.MOUSE_MOVE);

注销事件

handler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_CLICK)//移除左键点击事件