效果图

1.初始化场景

onMounted(() => {
  line()
})

let index = 0; //取索引值的点的位置
let num = 20; //从曲线上获取的数量
let points1, newLine1, bufferGeometry1;
let points2, newLine2, bufferGeometry2;



function line() {

}

2.场景中加入一条三维曲线

function line(){
  //创建一条平滑的三维曲线 给三个点  起始 中间  结尾
  const drawPointList1 = new THREE.CatmullRomCurve3([
    new THREE.Vector3(0, 20, -110),
    new THREE.Vector3(30, 35, -75),
    new THREE.Vector3(60, 20, 0)
  ])

  //平分为100段，分的越多曲线越丝滑
  points1 = drawPointList1.getPoints(101)

  //   创建曲线 设置材质
  let line1 = new THREE.Line(new THREE.BufferGeometry().setFromPoints(points1), new THREE.LineBasicMaterial({ color: "#fff" })); // 构建三维曲线

  //   加入场景
  scene.add(line1);

}

3.截取曲线片段并渲染材质

  newLine1 = new THREE.CatmullRomCurve3(points1.slice(index, index + num));//使用截取的片段点作为参数重新生成一条曲线
  newLine1.getSpacedPoints(1000); //细分成100个点
  var percentArr = [];
  for (var i = 0; i < newLine1.length; i++) {
    percentArr.push(i / newLine1.length);
  }
  var percentAttribue = new THREE.BufferAttribute(
    new Float32Array(percentArr),
    1
  );
  var colorArr = [];
  for (var i = 0; i < 101; i++) {
    var color1 = new THREE.Color(0xffffff);
    var color2 = new THREE.Color(0x59BE3E);
    var color = color1.lerp(color2, i / 101);
    colorArr.push(color.r, color.g, color.b);
  }
  bufferGeometry1 = new THREE.BufferGeometry().setFromPoints(newLine1);//创建用于管理几何体的顶点数据，并设置点队列
  bufferGeometry1.attributes.percent = percentAttribue;
  bufferGeometry1.attributes.color = new THREE.BufferAttribute(new Float32Array(colorArr), 3);
  const PointsMaterial = new THREE.PointsMaterial({  //创建点材质
    size: 1.0, //点大小
    vertexColors: true, //使用顶点颜色渲染
  });
  
  //加入场景
  scene.add(new THREE.Points(bufferGeometry1, PointsMaterial));

4.循环执行，使线动起来

function animate() {
  requestAnimationFrame(animate);
  renderer.render(scene, camera);
  moveOnCurve()
}

function moveOnCurve() {
  if (index <= 99) {
    index += 1
    bufferGeometry1.setFromPoints(new THREE.CatmullRomCurve3(points1.slice(index, index + num)).getSpacedPoints(100));
  } else {
    index = 0
  }
}