从Cesium.Ray和Cesium.Cartesian3创建Cesium.HeadingPitchRoll

Question

是否可以从一个Cesium.Ray和一个Cesium.HeadingPitchRoll创建一个Cesium.HeadingPitchRoll

如果是这样的话，我们会怎么做呢？

编辑1：

const hpr = Cesium.HeadingPitchRoll.fromDegrees(0, 0, 0)
const matrix3 = Cesium.Matrix3.fromHeadingPitchRoll(hpr)

// The UNIT_X vector is "forward" in Cesium.  We'll multiply the rotation
// matrix by that unit vector, to get our direction vector.
const direction = Cesium.Matrix3.multiplyByVector(
  matrix3,
  Cesium.Cartesian3.UNIT_X,
  new Cesium.Cartesian3()
)

const origin = Cesium.Cartesian3.fromDegrees(i.longitude, i.latitude, i.altitude)

// Now we can construct the Ray.
const ray = new Cesium.Ray(origin, direction)

const finalPoint = Cesium.Ray.getPoint(ray, i.altitude)
const e = map.viewer.entities.add({
  name: i.id,
  polyline: {
    positions: [origin, finalPoint],
    width: 4,
    arcType: Cesium.ArcType.NONE,
    material: new Cesium.PolylineArrowMaterialProperty(Cesium.Color.RED),
  },
})

当HPR设置为(0,0,0)时，结果是：

​

​

当音高为0时，我会期望光线与地平线平行，而不是像+45度那样。

Answer 1

是的，这是可能的。这两种对象包含不同类型的信息，因此请注意，在转换过程中不要丢失数据。

• 一个Ray有一个origin (笛卡尔位置)和一个direction，它只是一个单位向量，与一个完全的方向不一样。
• HeadingPitchRoll是一个全方位的方向。航向和俯仰一起工作，以确定一个特定的“前进”方向，而滚动表示围绕该方向矢量的旋转。此滚轮旋转不影响方向，因此不会对光线产生影响。

下面是代码：

// A Cesium Ray consists of an "origin" and a "direction".
// The origin is just a Cartesian3 from anywhere.
var origin = new Cesium.Cartesian3(1.0, 2.0, 3.0);

// For this question, "direction" comes from a HeadingPitchRoll.
// Let's establish an HPR here.
var heading = Cesium.Math.toRadians(0);  // YOUR VALUE HERE
var pitch = Cesium.Math.toRadians(0);    // YOUR VALUE HERE
var roll = Cesium.Math.toRadians(0);     // This one does nothing.

var hpr = new Cesium.HeadingPitchRoll(heading, pitch, roll);

// Next we need a direction vector from the HPR.  We'll use
// a rotation matrix (3x3) to do the conversion.
var matrix3 = Cesium.Matrix3.fromHeadingPitchRoll(hpr);

// The UNIT_X vector is "forward" in Cesium.  We'll multiply the rotation
// matrix by that unit vector, to get our direction vector.
var direction = Cesium.Matrix3.multiplyByVector(matrix3, Cesium.Cartesian3.UNIT_X,
    new Cesium.Cartesian3());

// Now we can construct the Ray.
var ray = new Cesium.Ray(origin, direction);

console.log('Ray: ' + JSON.stringify(ray));

如果您在这里显示的默认零标题/螺距下运行此操作，您将再次获得单元X向量：

雷：{“原点”：{“x”：1，"y":2，"z":3}，“方向”：{“x”：1，"y":0，“z”：0}

但如果你把音高设为45度：

var heading = Cesium.Math.toRadians(0);
var pitch = Cesium.Math.toRadians(45);

你会看到X方向朝+Z方向倾斜。

射线：{“原点”：{“x”：1，"y":2，"z":3}，“方向”：{“x”：0.7071067811865476，"y":0，“z”：0.7071067811865475}

正航向将X矢量旋转到-Y (顺时针方向，如上面+Z所示)。

var heading = Cesium.Math.toRadians(45);
var pitch = Cesium.Math.toRadians(0);

射线：{“原点”：{“x”：1，"y":2，"z":3}，“方向”：{“x”：0.7071067811865476，"y":-0.7071067811865475，“z”：0}

编辑：这个问题被修改了一点。该射线的方向需要在地球中心的固定框架，而不是局部向上的框架，为预期的用途。

这里有一个更长的演示，展示了如何处理这个问题。你也可以在沙堡上做观看现场演示。

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

const i = {
  id: 'test',
  longitude: -79,
  latitude: 40,
  altitude: 500
};

// Create the origin and hpr.
const origin = Cesium.Cartesian3.fromDegrees(i.longitude, i.latitude, i.altitude)

let hpr = Cesium.HeadingPitchRoll.fromDegrees(0, 0, 0)

// Cesium uses East-North-Up axes, where East is zero.  If you want North == Zero,
// you must subtract 90 degrees' worth of radians (pi/2).
hpr.heading -= Cesium.Math.PI_OVER_TWO

// We'll get the orientation, which is a quaternion.  This is specific to the
// location on the planet.  Also it comes in handy later for the 3D model vis.
const orientation = Cesium.Transforms.headingPitchRollQuaternion(origin, hpr);

// Get a Matrix3 version of that Quaternion.
const matrix3 = Cesium.Matrix3.fromQuaternion(orientation);

// The UNIT_X vector is "forward" in Cesium.  We'll multiply the rotation
// matrix by that unit vector, to get our direction vector.
const direction = Cesium.Matrix3.multiplyByVector(
  matrix3,
  Cesium.Cartesian3.UNIT_X,
  new Cesium.Cartesian3()
)


// Now we can construct the Ray.
const ray = new Cesium.Ray(origin, direction)

const finalPoint = Cesium.Ray.getPoint(ray, i.altitude)
const e = viewer.entities.add({
  name: i.id,
  polyline: {
    positions: [origin, finalPoint],
    width: 4,
    arcType: Cesium.ArcType.NONE,
    material: new Cesium.PolylineArrowMaterialProperty(Cesium.Color.RED),
  },
})

// Optionally, show an aircraft model with this HPR.
const m = viewer.entities.add({
  position: origin,
  orientation: orientation,
  model: {
    uri: "../SampleData/models/CesiumAir/Cesium_Air.glb",
    minimumPixelSize: 64,
  }
})

viewer.zoomTo(e)