【Cesium ：问题】Cesium4种获取鼠标点击位置和解决viewer.scene.pickPosition(e.position)不准的问题。

 

一、Cesium4种获取鼠标点击位置

Cesium获取鼠标点击位置：4种

1获取鼠标点的对应椭球面位置：世界坐标（Cartesian3）

通过 viewer.scene.camera.pickEllipsoid(movement.position, ellipsoid)获取，可以获取当前点击视线与椭球面相交处的坐标，其中ellipsoid是当前地球使用的椭球对象：viewer.scene.globe.ellipsoid。

var viewer = new Cesium.Viewer('cesiumContainer');

var handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function (movement) {
     var position = viewer.scene.camera.pickEllipsoid(movement.position, viewer.scene.globe.ellipsoid);
     console.log(position);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

2获取加载地形后对应的经纬度和高程：地标坐标

通过viewer.scene.globe.pick(ray, scene)获取，可以获取点击处地球表面的世界坐标，不包括模型、倾斜摄影表面。其中ray=viewer.camera.getPickRay(movement.position)。

var viewer = new Cesium.Viewer('cesiumContainer');

var handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function (movement) {
     var ray=viewer.camera.getPickRay(movement.position);
     var position = viewer.scene.globe.pick(ray, viewer.scene);
     console.log(position);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

3获取倾斜摄影或模型点击处的坐标：场景坐标

通过viewer.scene.pickPosition(movement.position)获取，根据窗口坐标，从场景的深度缓冲区中拾取相应的位置，返回笛卡尔坐标。

var viewer = new Cesium.Viewer('cesiumContainer');

var handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function (movement) {
     var position = viewer.scene.pickPosition(movement.position);
     console.log(position);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

4获取点击处屏幕坐标 ：屏幕坐标（鼠标点击位置距离canvas左上角的像素值）

var viewer = new Cesium.Viewer('cesiumContainer');

var handler= new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function (movement) {
     console.log(movement.position);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

 

二、解决viewer.scene.pickPosition(e.position)在没有3dTile模型下的笛卡尔坐标不准问题。

解决方法：viewer.scene.globe.depthTestAgainstTerrain = true; //默认为false

参考博客：Cesium的拾取问题总结

别人的试验结论：
1. globe.pick的结果相对稳定准确，不论地形深度检测开启与否，不论加载的是默认地形还是别的地形数据；
2. scene.pickPosition只有在开启地形深度检测，且不使用默认地形时是准确的。
注意点：
1. globe.pick只能求交地形； 2. scene.pickPosition不仅可以求交地形，还可以求交除地形以外其他所有写深度的物体。
所以使用时可以二者结合来使用。

var viewer = new Cesium.Viewer('cesiumContainer', {
    selectionIndicator : false,
    infoBox : false,
    // 注释时相当于使用默认地形，解开注释相当于使用全球地形
    //terrainProvider: Cesium.createWorldTerrain()
});

// 深度开启或关闭
viewer.scene.globe.depthTestAgainstTerrain = true; 

var scene = viewer.scene;
if (!scene.pickPositionSupported) {
    console.log('This browser does not support pickPosition.');
}

var handler;

Sandcastle.addToolbarButton('Pick position', function() {
    var modelEntity = viewer.entities.add({
        name : 'milktruck',
        position : Cesium.Cartesian3.fromDegrees(-123.0744619, 44.0503706),
        model : {
            uri : '../../SampleData/models/CesiumMilkTruck/CesiumMilkTruck-kmc.gltf'
        }
    });
    viewer.zoomTo(modelEntity);

    var labelEntity = viewer.entities.add({
        label : {
            show : false,
            showBackground : true,
            font : '14px monospace',
            horizontalOrigin : Cesium.HorizontalOrigin.LEFT,
            verticalOrigin : Cesium.VerticalOrigin.TOP,
            pixelOffset : new Cesium.Cartesian2(15, 0)
        }
    });

    var tempRay = new Cesium.Ray();
    var tempPos = new Cesium.Cartesian3();

    // Mouse over the globe to see the cartographic position
    handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
    handler.setInputAction(function(movement) {

        var foundPosition = false;

        var scene = viewer.scene;
        if (scene.mode !== Cesium.SceneMode.MORPHING) {
            //var pickedObject = scene.pick(movement.endPosition);
            if (true) {
                labelEntity.label.text = '';

                var cartesian = viewer.scene.pickPosition(movement.endPosition);

                if (Cesium.defined(cartesian)) {
                    var cartographic = Cesium.Cartographic.fromCartesian(cartesian);
                    var longitudeString = Cesium.Math.toDegrees(cartographic.longitude).toFixed(2);
                    var latitudeString = Cesium.Math.toDegrees(cartographic.latitude).toFixed(2);
                    var heightString = cartographic.height.toFixed(2);

                    labelEntity.label.text +=
                        'Lon: ' + ('   ' + longitudeString).slice(-7) + '\u00B0' +
                        '\nLat: ' + ('   ' + latitudeString).slice(-7) + '\u00B0' +
                        '\nAlt: ' + ('   ' + heightString).slice(-7) + 'm';        
                }

                var ray = scene.camera.getPickRay(movement.endPosition, tempRay);
                var cartesian2 = scene.globe.pick(ray, scene, tempPos);

                if (Cesium.defined(cartesian2)) {
                    var cartographic2 = Cesium.Cartographic.fromCartesian(cartesian2);
                    var longitudeString2 = Cesium.Math.toDegrees(cartographic2.longitude).toFixed(2);
                    var latitudeString2 = Cesium.Math.toDegrees(cartographic2.latitude).toFixed(2);
                    var heightString2 = cartographic2.height.toFixed(2);

                    labelEntity.label.text += 
                        '\nLon2: ' + ('   ' + longitudeString2).slice(-7) + '\u00B0' +
                        '\nLat2: ' + ('   ' + latitudeString2).slice(-7) + '\u00B0' +
                        '\nAlt2: ' + ('   ' + heightString2).slice(-7) + 'm';           
                }

                if (cartesian || cartesian2) {
                    labelEntity.position = cartesian || cartesian2;
                    labelEntity.label.show = true;  

                    labelEntity.label.eyeOffset = new Cesium.Cartesian3(0.0, 0.0, 0);
                    labelEntity.label.disableDepthTestDistance  = Number.POSITIVE_INFINITY;

                    foundPosition = true;            
                }
            }
        }

        if (!foundPosition) {
            labelEntity.label.show = false;
        }
    }, Cesium.ScreenSpaceEventType.MOUSE_MOVE);
});

Sandcastle.reset = function() {
    viewer.entities.removeAll();
    handler = handler && handler.destroy();
};