代碼

// 獲取當前三維范圍
function getCurrentExtent() {

    // 范圍對象
    var extent = {};
    
    // 得到當前三維場景
    var scene = viewer.scene;
    
    // 得到當前三維場景的橢球體
    var ellipsoid = scene.globe.ellipsoid;
    var canvas = scene.canvas;
    
    // canvas左上角
    var car3_lt = viewer.camera.pickEllipsoid(new Cesium.Cartesian2(0,0), ellipsoid);
    
    // canvas右下角
    var car3_rb = viewer.camera.pickEllipsoid(new Cesium.Cartesian2(canvas.width,canvas.height), ellipsoid);
    
    // 當canvas左上角和右下角全部在橢球體上
    if (car3_lt && car3_rb) {
        var carto_lt = ellipsoid.cartesianToCartographic(car3_lt);
        var carto_rb = ellipsoid.cartesianToCartographic(car3_rb);
        extent.xmin = Cesium.Math.toDegrees(carto_lt.longitude);
        extent.ymax = Cesium.Math.toDegrees(carto_lt.latitude);
        extent.xmax = Cesium.Math.toDegrees(carto_rb.longitude);
        extent.ymin = Cesium.Math.toDegrees(carto_rb.latitude);
    }
    
    // 當canvas左上角不在但右下角在橢球體上
    else if (!car3_lt && car3_rb) {
        var car3_lt2 = null;
        var yIndex = 0;
        do {
            // 這里每次10像素遞加，一是10像素相差不大，二是為了提高程序運行效率
            yIndex <= canvas.height ? yIndex += 10 : canvas.height;
            car3_lt2 = viewer.camera.pickEllipsoid(new Cesium.Cartesian2(0,yIndex), ellipsoid);
        }while (!car3_lt2);
        var carto_lt2 = ellipsoid.cartesianToCartographic(car3_lt2);
        var carto_rb2 = ellipsoid.cartesianToCartographic(car3_rb);
        extent.xmin = Cesium.Math.toDegrees(carto_lt2.longitude);
        extent.ymax = Cesium.Math.toDegrees(carto_lt2.latitude);
        extent.xmax = Cesium.Math.toDegrees(carto_rb2.longitude);
        extent.ymin = Cesium.Math.toDegrees(carto_rb2.latitude);
    }
    
    // 獲取高度
    extent.height = Math.ceil(viewer.camera.positionCartographic.height);
    return extent;
}