cesiumjs学习笔记之二——空间数据可视化
Cesium提供Entity API来绘制空间数据，例如点、标记、标签、线、3D模型、形状、立体形状（volume）。
Entity API简介
Cesium提供两类API：
- （1）面向图形开发人员的底层API，通常称为“Primitive API”。该API暴露最小限度的抽象，使用图形学术语，具有很大的灵活性，需要具有图形学编程的知识
- （2）高级别的数据驱动的API，称为“Entity API”。该API使用一致性设计的、高级别的对象来管理一组相关性的可视化对象，其底层使用Primitive API
下面是Entity API的简单例子，用红色半透明区域标记出美国怀俄明州：
var viewer = new Cesium.Viewer('cesiumContainer'); //创建一个查看器（Viewer widget）
var wyoming = viewer.entities.add({ //添加一个实体，仅需要传递一个简单JSON对象，返回值是一个Entity对象
name : 'Wyoming',
polygon : {
hierarchy : Cesium.Cartesian3.fromDegreesArray([//一组地理坐标
-109.080842,45.002073,
-105.91517,45.002073,
-104.058488,44.996596,
-104.053011,43.002989,
-104.053011,41.003906,
-105.728954,40.998429,
-107.919731,41.003906,
-109.04798,40.998429,
-111.047063,40.998429,
-111.047063,42.000709,
-111.047063,44.476286,
-111.05254,45.002073]),
material : Cesium.Color.RED.withAlpha(0.5), //材质
outline : true, //是否显示轮廓
outlineColor : Cesium.Color.BLACK //轮廓的颜色
}
});
viewer.zoomTo(wyoming);//缩放、平移视图使实体可见
形状与立体（Shapes and Volumes）
支持的形状与立体列表
（1）立方体(Boxes)：
var blueBox = viewer.entities.add({
name : 'Blue box',
//中心的位置
position: Cesium.Cartesian3.fromDegrees(-114.0, 40.0, 300000.0),
box : {
//长宽高
dimensions : new Cesium.Cartesian3(400000.0, 300000.0, 500000.0),
material : Cesium.Color.BLUE
}
});
var redBox = viewer.entities.add({
name : 'Red box with black outline',
position: Cesium.Cartesian3.fromDegrees(-107.0, 40.0, 300000.0),
box : {
dimensions : new Cesium.Cartesian3(400000.0, 300000.0, 500000.0),
material : Cesium.Color.RED,
outline : true, //显示轮廓
outlineColor : Cesium.Color.BLACK
}
});
var outlineOnly = viewer.entities.add({
name : 'Yellow box outline',
position: Cesium.Cartesian3.fromDegrees(-100.0, 40.0, 300000.0),
box : {
dimensions : new Cesium.Cartesian3(400000.0, 300000.0, 500000.0),
fill : false, //不显示填充
outline : true,
outlineColor : Cesium.Color.YELLOW
}
});（2）圆和椭圆(CirclesEllipses)
var viewer = new Cesium.Viewer('cesiumContainer');
//浮空的绿色圆形
var greenCircle = 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, //浮空
material : Cesium.Color.GREEN
}
});
//红色椭圆形，位于地表，带轮廓
var redEllipse = viewer.entities.add({
//不带高度
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
}
});
//蓝色椭圆柱，旋转了角度
var blueEllipse = viewer.entities.add({
position: Cesium.Cartesian3.fromDegrees(-95.0, 40.0, 100000.0),
name : 'Blue translucent, rotated, and extruded ellipse',
ellipse : {
semiMinorAxis : 150000.0,
semiMajorAxis : 300000.0,
extrudedHeight : 200000.0, //拉伸
rotation : Cesium.Math.toRadians(45), //旋转
material : Cesium.Color.BLUE.withAlpha(0.7),
outline : true
}
});
viewer.zoomTo(viewer.entities);(3)走廊(Corridor)
var redCorridor = 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
}
});
var greenCorridor = viewer.entities.add({
name : 'Green corridor at height with mitered corners',
corridor : {
positions : Cesium.Cartesian3.fromDegreesArray(
[ -90.0, 40.0,
-95.0, 40.0,
-95.0, 35.0
]),
height: 100000.0,
width : 200000.0,
cornerType: Cesium.CornerType.MITERED,
material : Cesium.Color.GREEN
}
});
var blueCorridor = viewer.entities.add({
name : 'Blue extruded corridor with beveled corners and outline',
corridor : {
positions : Cesium.Cartesian3.fromDegreesArray(
[ 80.0, 40.0,
-85.0, 40.0,
-85.0, 35.0
]),
height : 200000.0,
extrudedHeight : 100000.0,
width : 200000.0,
cornerType: Cesium.CornerType.BEVELED,
material : Cesium.Color.BLUE.withAlpha(0.5),
outline : true,
outlineColor : Cesium.Color.BLUE
}
});(4)圆柱和圆锥(Cylinder Cones)
var greenCylinder = viewer.entities.add({
name : 'Green cylinder with black outline',
position: Cesium.Cartesian3.fromDegrees(-100.0, 40.0, 200000.0),
cylinder : { //圆柱
length : 400000.0,
topRadius : 200000.0,
bottomRadius : 200000.0,
material : Cesium.Color.GREEN,
outline : true,
outlineColor : Cesium.Color.DARK_GREEN
}
});
var redCone = viewer.entities.add({
name : 'Red cone',
position: Cesium.Cartesian3.fromDegrees(-105.0, 40.0, 200000.0),
cylinder : {//圆锥
length : 400000.0,
topRadius : 0.0,
bottomRadius : 200000.0,
material : Cesium.Color.RED
}
});(5)多边形(Polygons)
var redPolygon = viewer.entities.add({
name : '贴着地表的多边形',
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
}
});
var greenPolygon = viewer.entities.add({
name : '绿色拉伸多边形',
polygon : {
hierarchy : Cesium.Cartesian3.fromDegreesArray([-108.0, 42.0,
-100.0, 42.0,
-104.0, 40.0]),
extrudedHeight: 500000.0,
material : Cesium.Color.GREEN
}
});
var orangePolygon = viewer.entities.add({
name : '每个顶点具有不同拉伸高度的橘色多边形',
polygon : {
hierarchy : Cesium.Cartesian3.fromDegreesArrayHeights(
[-108.0, 25.0, 100000,
-100.0, 25.0, 100000,
-100.0, 30.0, 100000,
-108.0, 30.0, 300000]),
extrudedHeight: 0,
perPositionHeight : true,
material : Cesium.Color.ORANGE,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});
var bluePolygon = viewer.entities.add({
name : '具有挖空效果的蓝色多边形',
polygon : {
hierarchy : {
positions : Cesium.Cartesian3.fromDegreesArray(
[-99.0, 30.0,
-85.0, 30.0,
-85.0, 40.0,
-99.0, 40.0]),
holes : [{
positions : Cesium.Cartesian3.fromDegreesArray([
-97.0, 31.0,
-97.0, 39.0,
-87.0, 39.0,
-87.0, 31.0
]),
holes : [{
positions : Cesium.Cartesian3.fromDegreesArray([
-95.0, 33.0,
-89.0, 33.0,
-89.0, 37.0,
-95.0, 37.0
]),
holes : [{
positions : Cesium.Cartesian3.fromDegreesArray([
-93.0, 34.0,
-91.0, 34.0,
-91.0, 36.0,
-93.0, 36.0
])
}]
}]
}]
},
material : Cesium.Color.BLUE,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});（6）多段线(Polylines)
var redLine = viewer.entities.add({
name : '沿着地球表面的红线',
polyline : {
positions : Cesium.Cartesian3.fromDegreesArray(
[-75, 35,
-125, 35]),
width : 5,
material : Cesium.Color.RED
}
});
var glowingLine = viewer.entities.add({
name : '具有发光效果的线',
polyline : {
positions : Cesium.Cartesian3.fromDegreesArray(
[-75, 37, -125, 37]
),
width : 10,
material : new Cesium.PolylineGlowMaterialProperty({
glowPower : 0.2,
color : Cesium.Color.BLUE
})
}
});
var orangeOutlined = viewer.entities.add({
name : '具有一定高度的线',
polyline : {
positions : Cesium.Cartesian3.fromDegreesArrayHeights(
[-75, 39, 250000,-125, 39, 250000]
),
width : 5,
material : new Cesium.PolylineOutlineMaterialProperty({
color : Cesium.Color.ORANGE,
outlineWidth : 2,
outlineColor : Cesium.Color.BLACK
})
}
});
var yellowLine = viewer.entities.add({
name : '不贴着地表的线',
polyline : {
positions : Cesium.Cartesian3.fromDegreesArrayHeights(
[-75, 43, 500000,-125, 43, 500000]
),
width : 3,
followSurface : false, //是否贴着地表
material : Cesium.Color.PURPLE
}
});（7）多段线体(Polyline Volumes)
var viewer = new Cesium.Viewer('cesiumContainer');
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;
}
function computeStar(arms, rOuter, rInner) {
var angle = Math.PI / arms;
var length = 2 * arms;
var positions = new Array(length);
for (var i = 0; i < length; i++) {
var r = (i % 2) === 0 ? rOuter : rInner;
positions[i] = new Cesium.Cartesian2(
Math.cos(i * angle) * r, Math.sin(i * angle) * r);
}
return positions;
}
var redTube = 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
}
});
var greenBox = viewer.entities.add({
name : 'Green box with beveled corners and outline',
polylineVolume : {
positions : Cesium.Cartesian3.fromDegreesArrayHeights(
[-90.0, 32.0, 0.0,
-90.0, 36.0, 100000.0,
-94.0, 36.0, 0.0]),
shape :[new Cesium.Cartesian2(-50000, -50000),
new Cesium.Cartesian2(50000, -50000),
new Cesium.Cartesian2(50000, 50000),
new Cesium.Cartesian2(-50000, 50000)],
cornerType : Cesium.CornerType.BEVELED,
material : Cesium.Color.GREEN,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});
var blueStar = viewer.entities.add({
name : 'Blue star with mitered corners and outline',
polylineVolume : {
positions : Cesium.Cartesian3.fromDegreesArrayHeights(
[-95.0, 32.0, 0.0,
-95.0, 36.0, 100000.0,
-99.0, 36.0, 200000.0]),
shape : computeStar(7, 70000, 50000),
cornerType : Cesium.CornerType.MITERED,
material : Cesium.Color.BLUE,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});
viewer.zoomTo(viewer.entities);（8）矩形(Rectangles)
//红色矩形 var redRectangle = viewer.entities.add({ name : 'Red translucent rectangle with outline', rectangle : { coordinates : Cesium.Rectangle.fromDegrees(-110.0, 20.0, -80.0, 25.0), material : Cesium.Color.RED.withAlpha(0.5), outline : true, outlineColor : Cesium.Color.RED } }); //绿色旋转、拉伸的矩形 var greenRectangle = viewer.entities.add({ name : 'Green translucent, rotated, and extruded rectangle', rectangle : { coordinates : Cesium.Rectangle.fromDegrees(-100.0, 30.0, -90.0, 40.0), material : Cesium.Color.GREEN.withAlpha(0.5), rotation : Cesium.Math.toRadians(45), extrudedHeight : 300000.0, height : 100000.0, outline : true, outlineColor : Cesium.Color.GREEN }});
9）球和椭球(Spheres Ellipsoids)
var blueEllipsoid = viewer.entities.add({ name : 'Blue ellipsoid', position: Cesium.Cartesian3.fromDegrees(-114.0, 40.0, 300000.0), ellipsoid : { //可以指定三个轴的半径 radii : new Cesium.Cartesian3(200000.0, 200000.0, 300000.0), material : Cesium.Color.BLUE } }); var redSphere = viewer.entities.add({ name : 'Red sphere with black outline', position: Cesium.Cartesian3.fromDegrees(-107.0, 40.0, 300000.0), ellipsoid : { //正球体 radii : new Cesium.Cartesian3(300000.0, 300000.0, 300000.0), material : Cesium.Color.RED, outline : true, outlineColor : Cesium.Color.BLACK } }); var outlineOnly = viewer.entities.add({ name : 'Yellow ellipsoid outline', position: Cesium.Cartesian3.fromDegrees(-100.0, 40.0, 300000.0), ellipsoid : { radii : new Cesium.Cartesian3(200000.0, 200000.0, 300000.0), fill : false, outline : true, outlineColor : Cesium.Color.YELLOW, slicePartitions : 24, //横向切割线 stackPartitions : 36 //纵向切割线 } });(10)墙(Walls)
//东西方向的横墙
var redWall = viewer.entities.add({
name : 'Red wall at height',
wall : {
positions : Cesium.Cartesian3.fromDegreesArrayHeights(
[-115.0, 44.0, 200000.0,//坐标点
-90.0, 44.0, 200000.0]
),
minimumHeights : [100000.0, 100000.0], //按坐标点的最小高度数组
material : Cesium.Color.RED
}
});
//四边围墙
var greenWall = 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,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});
//曲折的墙
var blueWall = viewer.entities.add({
name : 'Blue wall with sawtooth heights and outline',
wall : {
//坐标点，不指定高度
positions : Cesium.Cartesian3.fromDegreesArray(
[-115.0, 50.0,
-112.5, 50.0,
-110.0, 50.0,
-107.5, 50.0,
-105.0, 50.0,
-102.5, 50.0,
-100.0, 50.0,
-97.5, 50.0,
-95.0, 50.0,
-92.5, 50.0,
-90.0, 50.0]),
maximumHeights : [ //上高
100000, 200000, 100000, 200000, 100000, 200000,
100000, 200000, 100000, 200000, 100000],
minimumHeights : [ //下高
0, 100000, 0, 100000, 0, 100000, 0, 100000, 0,
100000, 0],
material : Cesium.Color.BLUE,
outline : true,
outlineColor : Cesium.Color.BLACK
}
});材质（Material）与轮廓（Outline）
多数形状均支持通过一致的方式来设置属性、控制外观：
- （1）fill：布尔型，用于指定目标形状是否被填充
- （2）outline：布尔型，用于指定是否绘制形状的边缘
- （3）material：如果fill为true，该属性可以控制填充的材质类型
一个例外是多段线，可以设置outlineWidth 、outlineColor、glowPower 等属性。
高度与拉伸（Extrusion）所有的形状均默认均是沿着地表的，目前圆形、椭圆、矩形可以在一定高度浮空显示，或者拉伸为Volume。
需要注意：Cesium总是使用米、弧度、秒为度量单位。下面是一个例子：
wyoming.polygon.height = 200000; //设置高度
wyoming.polygon.extrudedHeight = 250000; //设置拉伸高度除非显式禁用，点击实体后会显示SelectionIndicator小器件，以及一个信息框。通过设置Entity.description，可以在信息框中显示任何HTML内容。
镜头控制zoomTo方法可以立即定位到某个位置，而flyTo则是通过动画方式转移到某个位置，这两个方法均可以传递EntityCollection对象，并且均是异步方法，返回一个Promises对象
默认情况下，镜头是朝北、45度倾斜查看地球。下面的代码可以让镜头朝东、倾斜三十度查看：
//镜头顺时针旋转九十度，即东向
var heading = Cesium.Math.toRadians(90);
//镜头倾斜30度俯视
var pitch = Cesium.Math.toRadians(-30);
viewer.zoomTo(wyoming, new Cesium.HeadingPitchRange(heading, pitch)).then(function(result){
//执行完毕后，进行的动作
if (result) { //如果镜头切换成功，则result=true
viewer.selectedEntity = wyoming;
}
});有时需要镜头跟踪某个实体（使居中）而不是地球，可以使用如下代码：
wyoming.position = Cesium.Cartesian3.fromDegrees(-107.724, 42.68);
viewer.trackedEntity = wyoming; //跟踪某个实体。如果调用zoomTo、flyTo自动取消跟踪管理Entity
EntityCollection对象是一个从Entity Id到Entity的关联数组，其提供例如add、remove、removeAll之类的常规函数，用于添加或者删除某个Entity：
//添加一个实体，并且提供ID
viewer.entities.add({
id : '182bdba4-2b3e-47ae-bf0b-83f6fde285fd'
});
//获取一个实体
var entity = viewer.entities.getById('uniqueId')
//获取一个实体，如果不存在则创建之
var entity = viewer.entities.getOrCreateEntity('uniqueId');
//当添加、删除、修改EntityCollection中的Entity时，可以获得事件通知
function onChanged(collection, added, removed, changed){
//add、removed、changed是增删改的Entity数组
for(var i = 0; i < added.length; i++) {
}
}
viewer.entities.collectionChanged.addEventListener(onChanged);
//大批量操作时，临时禁用事件可以提高性能
viewer.entities.suspendEvents();
//执行各种Entity操作
viewer.entities.resumeEvents();点、图标和标签
添加一个点、标签或者图标很简单：
var viewer = new Cesium.Viewer( 'cesiumContainer' );
var citizensBankPark = viewer.entities.add( {
name : 'Citizens Bank Park',
position : Cesium.Cartesian3.fromDegrees( -75.166493, 39.9060534 ),
point : { //点
pixelSize : 5,
color : Cesium.Color.RED,
outlineColor : Cesium.Color.WHITE,
outlineWidth : 2
},
label : { //文字标签
text : 'Citizens Bank Park',
font : '14pt monospace',
style : Cesium.LabelStyle.FILL_AND_OUTLINE,
outlineWidth : 2,
verticalOrigin : Cesium.VerticalOrigin.BOTTOM, //垂直方向以底部来计算标签的位置
pixelOffset : new Cesium.Cartesian2( 0, -9 ) //偏移量
}
billboard : { //图标
image : 'http://localhost:81/images/2015/02-02/Philadelphia_Phillies.png',
width : 64,
height : 64
},
} );
viewer.zoomTo( viewer.entities );3D模型
Cesium支持glTF格式的3D模型，glTF是WebGL、OpenGL ES、 OpenGL的一种运行时模型格式，在Cesium中创建3D模型很简单：
var viewer = new Cesium.Viewer('cesiumContainer');
var entity = viewer.entities.add({
position : Cesium.Cartesian3.fromDegrees(-123.0744619, 44.0503706),
model : {
uri : '../../SampleData/models/CesiumGround/Cesium_Ground.gltf'
},
scale : 1,//和原始大小相比的缩放比例
minimumPixelSize :100 //最小尺寸，防止太小而看不见
});
viewer.trackedEntity = entity;
默认情况下，模型竖直放置、并且面向东面。可以指定四元组（Quaternion）给Entity.orientation属性，以改变放置的方向：
var viewer = new Cesium.Viewer('cesiumContainer');
var position = Cesium.Cartesian3.fromDegrees(-123.0744619, 44.0503706); //位置
var heading = Cesium.Math.toRadians(45.0);//绕垂直于地心的轴旋转
var pitch = Cesium.Math.toRadians(15.0); //绕纬度线旋转
var roll = Cesium.Math.toRadians(0.0); //绕经度线旋转
var orientation = Cesium.Transforms.headingPitchRollQuaternion(position, heading, pitch, roll);
var entity = viewer.entities.add({
position : position,
orientation : orientation,
model : {
uri : '../../SampleData/models/CesiumGround/Cesium_Ground.gltf'
}
});
viewer.trackedEntity = entity;属性 系统
Cesium提供了一些快捷方式来设置属性，例如outline:true，但是尝试使用e.polygon.outline这样的形式来获取轮廓时，会得到一个ConstantProperty对象，如果不使用快捷方式，则需要编写更多的代码，例如：
polygon.outline = new Cesium.ConstantProperty(true);
polygon.outlineColor = new Cesium.ConstantProperty(Cesium.Color.BLACK);所有属性的实例均是Property的子类型，引入属性类层次而不是使用基本类型的原因是，某些属性是随着时间而变化的。
要得到属性的原始值，需要调用Property.getValue()方法，例如：
//获取当前时间点，多边形轮廓是否存在
polygon.outline.getValue(viewer.clock.currentTime)原文：http://www.2cto.com/kf/201607/525153.html
所有发生在我们身上的事件都是一个经过仔细包装的礼物。只要我们愿意面对它有时候有点丑恶的包装，带着耐心和勇气一点一点的拆开包装的话，我们会惊喜的看到里面珍藏的礼物。
----遇见未知的自己
