向量点乘

向量点乘

• 概述

概述

使用three.js画两条线，通过点乘来计算夹角

1. 画两条线段

  let v1 = new THREE.Vector3(0, 0, 0);
  let v2 = new THREE.Vector3(10, 2, 0);
  let v3 = new THREE.Vector3(0, 10, 0);
  let geometry1 = new THREE.Geometry();
  geometry1.vertices.push(v1, v2);
  let material1 = new THREE.LineBasicMaterial({
    color: 0x0000ff
  });
  let line1 = new THREE.Line(geometry1, material1);
  scene.add(line1);

  let geometry2 = new THREE.Geometry();
  geometry2.vertices.push(v1, v3);
  let material2 = new THREE.LineBasicMaterial({
    color: 0xff0000
  });
  let line2 = new THREE.Line(geometry2, material2);
  scene.add(line2);

效果：

2. 使用点乘来计算夹角余弦值和角度。

  // 返回三角形顶点p1对应夹角余弦值
  let dot = v2.clone().normalize().dot(v3.clone().normalize());
  console.log(dot);  // 结果为0
  console.log(Math.acos(dot)*180/Math.PI); // 结果为90