<script src="/js/threejs/threer92.js"></script>
<script src="/example/threejs/solarsystem/files/OrbitControls.js"></script>
var scene = new THREE.Scene();
var geometry = new THREE.BufferGeometry();
var arc = new THREE.ArcCurve(0, 0, R, 0, Math.PI, true);
var line1 = new THREE.LineCurve(new THREE.Vector2(R, 200, 0), new THREE.Vector2(R, 0, 0));
var line2 = new THREE.LineCurve(new THREE.Vector2(-R, 0, 0), new THREE.Vector2(-R, 200, 0));
var CurvePath = new THREE.CurvePath();
CurvePath.curves.push(line1, arc, line2);
var points = CurvePath.getPoints(200);
geometry.setFromPoints(points);
var material = new THREE.LineBasicMaterial({
var line = new THREE.Line(geometry, material);