Cartesian的翻译为"笛卡尔"，实际上Cartesian3是来储存点的X/Y/Z坐标的，其中的方法也是服务于这一点，请大家记住这一点。以下就简称之为C3。
一、经纬度转换为世界坐标
1.Cesium.Cartesian3.fromDegrees(longitude, latitude, height, ellipsoid, result)
2.var ellipsoid=viewer.scene.globe.ellipsoid;
var cartographic=Cesium.Cartographic.fromDegrees(lng,lat,alt);
var cartesian3=ellipsoid.cartographicToCartesian(cartographic);
二、 世界坐标转换为经纬度
1.var ellipsoid=viewer.scene.globe.ellipsoid;
var cartesian3=new Cesium.cartesian3(x,y,z);
var cartographic=ellipsoid.cartesianToCartographic(cartesian3);
var lat=Cesium.Math.toDegrees(cartograhphic.latitude);
var lng=Cesium.Math.toDegrees(cartograhpinc.longitude);
var alt=cartographic.height;
2.Cartographic.fromCartesian
三、屏幕坐标和世界坐标相互转换
1.var pick1= new Cesium.Cartesian2(0,0);
var cartesian = viewer.scene.globe.pick(viewer.camera.getPickRay(pick1),viewer.scene);
2.Cesium.SceneTransforms.wgs84ToWindowCoordinates(scene, Cartesian3);
Cartesian3的方法和属性：
.fromSpherical函数：Converts the provided Spherical into Cartesian3 coordinates
把球形转化为C3坐标
.fromElements函数：Creates a Cartesian3 instance from x, y and z coordinates.
使用X/Y/Z坐标给C3赋值
.clone函数：Duplicates a Cartesian3 instance.
复制C3实例并返回
.fromCartesian4对象：Creates a Cartesian3 instance from an existing Cartesian4. This simply takes the x, y, and z properties of the Cartesian4 and drops w.
函数方法与clone函数相同，即返回值为C3实例
.packedLength对象：The number of elements used to pack the object into an array.
返回值为3
.pack函数：Stores the provided instance into the provided array.
将提供的实例置入数组(可以为空)中，返回该数组
.unpack函数：Retrieves an instance from a packed array
从数组中根据位置检索一个实例并返回
array的数据结构：[ x , y , z , x , y , z , x , y , z , x ……]
.packArray函数：Flattens an array of Cartesian3s into an array of components.
由C3的数组转换为一维的数组，并返回
.unpackArray函数：Unpacks an array of cartesian components into an array of Cartesian3s.
由一维的数组转换为C3的数组，并返回
C3数组的数据结构：[C3_1 , C3_2 , C3_3 ……]
.fromArray对象：Creates a Cartesian3 from three consecutive elements in an array.
为unpack函数的返回值
.maximumComponent函数：Computes the value of the maximum component for the supplied Cartesian.
计算C3中X/Y/Z的最大值并返回
.minimumComponent函数：Computes the value of the minimum component for the supplied Cartesian.
计算C3中X/Y/Z的最小值并返回
.minimumByComponent函数：Compares two Cartesians and computes a Cartesian which contains the minimum components of the supplied Cartesians.
分别比较两个C3实例的X/Y/Z并返回一个各坐标均为最小的CS实例
.maximumByComponent函数：Compares two Cartesians and computes a Cartesian which contains the maximum components of the supplied Cartesians.
分别比较两个C3实例的X/Y/Z并返回一个各坐标均为最大的CS实例
.magnitudeSquared函数：Computes the provided Cartesian's squared magnitude.
计算X/Y/Z的平方和并返回
.magnitude函数：Computes the Cartesian's magnitude (length).
进行magnitudeSquared后的根号计算并返回
.distance函数：Computes the distance between two points.
计算两个点之间的距离
.distanceSquared函数：Computes the squared distance between two points. Comparing squared distances
计算两点之间的距离的平方根
.normalize函数：Computes the normalized form of the supplied Cartesian.
计算成为统一的C3格式
.dot函数：Computes the dot (scalar) product of two Cartesians.(物理意义是什么？经常用到)
计算两个Cartesian的点（标量）乘积
.multiplyComponents函数：Computes the componentwise product of two Cartesians.
计算两个C3实例的乘积(分量积)后的C3实例
.divideComponents函数：Computes the componentwise quotient of two Cartesians.
计算两个C3实例的相除(分量商)后的C3实例
.add函数：Computes the componentwise sum of two Cartesians.
计算两个C3实例的相加(分量和)后的C3实例
.subtract函数：Computes the componentwise difference of two Cartesians.
计算两个C3实例的相减(分量差)后的C3实例
.multiplyByScalar函数：Multiplies the provided Cartesian componentwise by the provided scalar.
计算C3实例与已知级别相乘并返回
.divideByScalar函数：Multiplies the provided Cartesian componentwise by the provided scalar.
计算C3实例与已知级别相除并返回
.negate函数：Negates the provided Cartesian.
计算C3实例的相反数并返回
.abs函数：Computes the absolute value of the provided Cartesian.
计算C3实例的绝对值并返回
.lerp函数：Computes the linear interpolation or extrapolation at t using the provided cartesians.
根据t的值和两个C3实例(对t来说，一个对应的值为0，一个为1)进行内插或外推
.angleBetween函数：Returns the angle, in radians, between the provided Cartesians.
以弧度制单位返回两个C3实例间的角度
.mostOrthogonalAxis函数：Returns the axis that is most orthogonal to the provided Cartesian.(还不是很懂)
返回与提供的C3实例正交的轴
.projectVector函数：Projects vector a onto vector b
把向量a投影到向量b上返回其结果
.equals函数：Compares the provided Cartesians componentwise and returns
比较两个C3实例是否相同
.equalsArray函数：private
比较C3实例是否与数组中某偏移量后的X/Y/Z相同
.equalsEpsilon函数：Compares the provided Cartesians componentwise and returns
根据一定的容忍度(误差圆)来判断两个C3实例是否相等
.cross函数：Computes the cross (outer) product of two Cartesians.(还不是很懂)
计算两个C3实例之间的叉积
.fromDegrees函数：Returns a Cartesian3 position from longitude and latitude values given in degrees.
由经纬度(角度单位)计算C3坐标并返回，通过调用fromRadians函数
.fromRadians函数：Returns a Cartesian3 position from longitude and latitude values given in radians.
由给定的经纬度(弧度单位)计算C3并返回
.fromDegreesArray函数：Returns an array of Cartesian3 positions given an array of longitude and latitude values given in degrees.
由给定的经纬度(角度单位)数组生成一个C3数组并返回
.fromRadiansArray函数：Returns an array of Cartesian3 positions given an array of longitude and latitude values given in radians.
由给定的经纬度(弧度单位)数组生成一个C3数组并返回
.fromDegreesArrayHeights函数：Returns an array of Cartesian3 positions given an array of longitude, latitude and height values where longitude and latitude are given in degrees.
由给定的坐标数据(角度单位)的数组生成一个C3数组并返回，数组数据结构如下
[-115.0, 37.0, 100000.0, -107.0, 33.0, 150000.0 ……]
.fromRadiansArrayHeights函数：Returns an array of Cartesian3 positions given an array of longitude, latitude and height values where longitude and latitude are given in radians.
由给定的坐标数据(角度单位)的数组生成一个C3数组并返回，数组数据结构如下
[-2.007, 0.645, 100000.0, -1.867, .575, 150000.0 ……]
.ZERO对象：An immutable Cartesian3 instance initialized to (0.0, 0.0, 0.0).
.UNIT_X对象：An immutable Cartesian3 instance initialized to (1.0, 0.0, 0.0).
.UNIT_Y对象：An immutable Cartesian3 instance initialized to (0.0, 1.0, 0.0).
.UNIT_Z对象：An immutable Cartesian3 instance initialized to (0.0, 0.0, 1.0).
.prototype.clone函数：Duplicates this Cartesian3 instance.
调用clone函数，复制这个C3实例并返回
.prototype.equals函数：Compares this Cartesian against the provided Cartesian componentwise and returns
调用equals函数，比较该实例与给定实例的相等关系
.prototype.equalsEpsilon函数：Compares this Cartesian against the provided Cartesian componentwise and returns
调用equalsEpsilon函数，比较该实例域给定实例在误差范围内(给定的容忍度)的比较结果
.prototype.toString函数：Creates a string representing this Cartesian in the format '(x, y, z)'.
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