Three.js半球

Question

我按照Create a concave half sphere with three.js的建议在Three.js中创建半球，我计划将一些鱼眼视频映射到。示例（镜头盖打开）here

我只是想让球体先显示出来，每当我尝试将它变成半球时它就会消失。

请在此处查看代码 http://codepen.io/bknill/pen/vXBWGv

var geometry = new THREE.SphereGeometry( 5000,16,16, Math.PI/2, Math.PI*2, 0, Math.PI);

var material = new THREE.MeshBasicMaterial( { color: 0x2980b9} );
material.side = THREE.BackSide;

var sphere = new THREE.Mesh( geometry, material );

scene.add( sphere );

任何人都可以先让我知道如何让这个半球出现吗？