cesium中orientation可以设置朝向，由position和HeadingPitchRoll共同决定，类型为headingPitchRollQuaternion，值是一个四元数。

一、设置orientation

// entity位置
let position = Cesium.Cartesian3.fromDegrees(113.295660, 38.1905, 0);

// orientation
let orientation = Cesium.Transforms.headingPitchRollQuaternion(
        position,
        new Cesium.HeadingPitchRoll(Cesium.Math.toRadians(10), Cesium.Math.toRadians(20), Cesium.Math.toRadians(30)),
      );

二、orientation转hpr，得到对应的HeadingPitchRoll

// 四元数计算三维旋转矩阵
let mtx3 = Cesium.Matrix3.fromQuaternion(orientation, new Cesium.Matrix3());

// 四维转换矩阵
let mtx4 = Cesium.Matrix4.fromRotationTranslation(mtx3, position, new Cesium.Matrix4());

// 计算HeadingPitchRoll，结果为弧度
let hpr = Cesium.Transforms.fixedFrameToHeadingPitchRoll(
        mtx4,
        Cesium.Ellipsoid.WGS84,
        Cesium.Transforms.eastNorthUpToFixedFrame,
        new Cesium.HeadingPitchRoll(),
      );

// 转成角度
let heading = Cesium.Math.toDegrees(hpr.heading);
let pitch= Cesium.Math.toDegrees(hpr.pitch);
let roll= Cesium.Math.toDegrees(hpr.roll);