局部坐标系使用

背景

已知一个中心点（Cartesian3），长（100 米），宽（70 米），计算矩形的顶点坐标

初次尝试

直接使用以下方式计算

const rectWidth = 100;

const rectHeight = 70;

const minX = center.x - rectWidth / 2;

const minY = center.y - rectHeight / 2;

const maxX = center.x + rectWidth / 2;

const maxY = center.y + rectHeight / 2;

结果结算出结果误差太大，导致矩形变形严重，完全不符合要求

使用局部坐标系

const rectWidth = 100;

const rectHeight = 70;

const origin = {
  x: 0,
  y: 0,
};

const minX = origin.x - this.rectWidth / 2;

const minY = origin.y - this.rectHeight / 2;

const maxX = origin.x + this.rectWidth / 2;

const maxY = origin.y + this.rectHeight / 2;

// 使用eastNorthUpToFixedFrame方法计算出已指定点（center）为原点的局部参考系转换矩阵
let localMatrix4 = this.cesium.Transforms.eastNorthUpToFixedFrame(center);

// 然后使用multiplyByPoint计算相对于原点的其他坐标的实际笛卡尔坐标
const westSouth = this.cesium.Matrix4.multiplyByPoint(
  localMatrix4,
  new this.cesium.Cartesian3(minX, minY, 0),
  new this.cesium.Cartesian3()
);

const westNorth = this.cesium.Matrix4.multiplyByPoint(
  localMatrix4,
  new this.cesium.Cartesian3(minX, maxY, 0),
  new this.cesium.Cartesian3()
);

const eastSouth = this.cesium.Matrix4.multiplyByPoint(
  localMatrix4,
  new this.cesium.Cartesian3(maxX, minY, 0),
  new this.cesium.Cartesian3()
);

const eastNorth = this.cesium.Matrix4.multiplyByPoint(
  localMatrix4,
  new this.cesium.Cartesian3(maxX, maxY, 0),
  new this.cesium.Cartesian3()
);