三.如何用曲线边画形状

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.set(3, 5, 8);
var renderer = new THREE.WebGLRenderer({
  antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

var controls = new THREE.OrbitControls(camera, renderer.domElement);

scene.add(new THREE.GridHelper(10, 10));

var Shape = new THREE.Shape();
Shape.absarc(2, 4, 2, Math.PI, Math.PI * 2);
Shape.lineTo(4, 0);
Shape.lineTo(0, 0);

var shapeGeom = new THREE.ShapeBufferGeometry(Shape);
var shapeMaterial = new THREE.MeshBasicMaterial({
  color: 0x00ff00,
  side: THREE.DoubleSide
});
var shapeMesh = new THREE.Mesh(shapeGeom, shapeMaterial);
scene.add(shapeMesh);

render();

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

body {
  overflow: hidden;
  margin: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/96/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>