Cesium using dynamic plotting points, lines, polygons, circles, rectangles

Copy the following code to https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/?src=Drawing%20on%20Terrain.html View Demo.

var activeShapePoints = [];
var activeShape;
var floatingPoint;

//查看器
var viewer = new Cesium.Viewer('cesiumContainer', {
    selectionIndicator: false,
    infoBox: false,
    terrainProvider: Cesium.createWorldTerrain()
});

var handler = new Cesium.ScreenSpaceEventHandler(viewer.canvas);

//双击鼠标左键清除默认事件
viewer.cesiumWidget.screenSpaceEventHandler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_DOUBLE_CLICK);
//绘制点
function createPoint(worldPosition) {
    var point = viewer.entities.add({
        position: worldPosition,
        point: {
            color: Cesium.Color.WHITE,
            pixelSize: 5,
            heightReference: Cesium.HeightReference.CLAMP_TO_GROUND
        }
    });
    return point;
}
//初始化为线
var drawingMode = 'line';
//绘制图形
function drawShape(positionData) {
    var shape;
    if (drawingMode === 'line') {
        shape = viewer.entities.add({
            polyline: {
                positions: positionData,
                clampToGround: true,
                width: 3
            }
        });
    }
    else if (drawingMode === 'polygon') {
        shape = viewer.entities.add({
            polygon: {
                hierarchy: positionData,
                material: new Cesium.ColorMaterialProperty(Cesium.Color.WHITE.withAlpha(0.7))
            }
        });
    } else if (drawingMode === 'circle') {
        //当positionData为数组时绘制最终图，如果为function则绘制动态图
        var value = typeof positionData.getValue === 'function' ? positionData.getValue(0) : positionData;
        //var start = activeShapePoints[0];
        //var end = activeShapePoints[activeShapePoints.length - 1];
        //var r = Math.sqrt(Math.pow(start.x - end.x, 2) + Math.pow(start.y - end.y, 2));
        //r = r ? r : r + 1;
        shape = viewer.entities.add({
            position: activeShapePoints[0],
            name: 'Blue translucent, rotated, and extruded ellipse with outline',
            type:'Selection tool',
            ellipse: {
                semiMinorAxis: new Cesium.CallbackProperty(function () {
                    //半径 两点间距离
                    var r = Math.sqrt(Math.pow(value[0].x - value[value.length - 1].x, 2) + Math.pow(value[0].y - value[value.length - 1].y, 2));
                    return r ? r : r + 1;
                }, false),
                semiMajorAxis: new Cesium.CallbackProperty(function () {
                    var r = Math.sqrt(Math.pow(value[0].x - value[value.length - 1].x, 2) + Math.pow(value[0].y - value[value.length - 1].y, 2));
                    return r ? r : r + 1;
                }, false),
                material: Cesium.Color.BLUE.withAlpha(0.5),
                outline: true
            }
        });
    } else if (drawingMode === 'rectangle') {
        //当positionData为数组时绘制最终图，如果为function则绘制动态图
        var arr = typeof positionData.getValue === 'function' ? positionData.getValue(0) : positionData;
        shape = viewer.entities.add({
            name: 'Blue translucent, rotated, and extruded ellipse with outline',
            rectangle : {
                coordinates :  new Cesium.CallbackProperty(function () {
                    var obj=Cesium.Rectangle.fromCartesianArray(arr);
                    //if(obj.west==obj.east){ obj.east+=0.000001};
                    //if(obj.south==obj.north){obj.north+=0.000001};
                    return obj;
                }, false),
                material : Cesium.Color.RED.withAlpha(0.5)
            }
        });
    }
    return shape;
}
//鼠标左键
handler.setInputAction(function (event) {
    // We use `viewer.scene.pickPosition` here instead of `viewer.camera.pickEllipsoid` so that
    // we get the correct point when mousing over terrain.
    var earthPosition = viewer.scene.pickPosition(event.position);
    // `earthPosition` will be undefined if our mouse is not over the globe.
    if (Cesium.defined(earthPosition)) {
        if (activeShapePoints.length === 0) {
            floatingPoint = createPoint(earthPosition);
            activeShapePoints.push(earthPosition);
            var dynamicPositions = new Cesium.CallbackProperty(function () {
                return activeShapePoints;
            }, false);
            activeShape = drawShape(dynamicPositions);//绘制动态图
        }
        activeShapePoints.push(earthPosition);
        createPoint(earthPosition);
    }
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);
//鼠标移动
handler.setInputAction(function (event) {
    if (Cesium.defined(floatingPoint)) {
        var newPosition = viewer.scene.pickPosition(event.endPosition);
        if (Cesium.defined(newPosition)) {
            floatingPoint.position.setValue(newPosition);
            activeShapePoints.pop();
            activeShapePoints.push(newPosition);
        }
    }
}, Cesium.ScreenSpaceEventType.MOUSE_MOVE);

// Redraw the shape so it's not dynamic and remove the dynamic shape.
function terminateShape() {
    activeShapePoints.pop();//去除最后一个动态点
    if(activeShapePoints.length){
       drawShape(activeShapePoints);//绘制最终图
    }
    viewer.entities.remove(floatingPoint);//去除动态点图形（当前鼠标点）
    viewer.entities.remove(activeShape);//去除动态图形
    floatingPoint = undefined;
    activeShape = undefined;
    activeShapePoints = [];
}

handler.setInputAction(function (event) {
    terminateShape();
}, Cesium.ScreenSpaceEventType.RIGHT_CLICK);

var options = [{
    text: 'Draw Lines',
    onselect: function () {
        terminateShape();
        drawingMode = 'line';
    }
}, {
    text: 'Draw Polygons',
    onselect: function () {
        terminateShape();
        drawingMode = 'polygon';
    }
}, {
    text: 'Draw Circle',
    onselect: function () {
        terminateShape();
        drawingMode = 'circle';
    }
}, {
    text: 'Draw Rectangle',
    onselect: function () {
        terminateShape();
        drawingMode = 'rectangle';
    }
}];

Sandcastle.addToolbarMenu(options);
// Zoom in to an area with mountains
viewer.camera.lookAt(Cesium.Cartesian3.fromDegrees(-122.2058, 46.1955, 1000.0), new Cesium.Cartesian3(5000.0, 5000.0, 5000.0));
viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);

Reference https://github.com/K-UTIL/cesiumjs-demo/blob/master/Source/demo.js
https://blog.csdn.net/weixin_33774883/article/details/87495638