var line2 = new THREE.LineCurve(new THREE.Vector2(-R, 0, 0), new THREE.Vector2(-R, 200, 0));
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style>
body {
margin: 0;
overflow: hidden;
/* 隐藏body窗口区域滚动条 */
}
</style>
<!--引入three.js三维引擎-->
<script src="/js/threejs/threer92.js"></script>
<script src="/example/threejs/solarsystem/files/OrbitControls.js"></script>
</head>
<body>
<script>
//创建场景
var scene = new THREE.Scene();
var geometry = new THREE.BufferGeometry(); //声明一个几何体对象
// 绘制一个U型轮廓
var R = 80;//圆弧半径