谁能看看什么原因，模拟器上没问题，但是手机上不显示，也不报错

var THREE = require('./js/libs/three.js')

var pmwidth = canvas.width

var pmheight = canvas.height

var canvasa = wx.createCanvas()

var context = canvasa.getContext('webgl');

var scene = new THREE.Scene();

var camera = new THREE.PerspectiveCamera(75, pmwidth / pmheight, 0.1, 1000);

var renderer = new THREE.WebGLRenderer(context);

renderer.setSize(pmwidth, pmheight);

canvasa.appendChild(renderer.domElement);

var geometry = new THREE.CubeGeometry(1, 1, 1);

var material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });

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

scene.add(cube);

camera.position.z = 5;

var ctx

var bgcolor

function render() {

 requestAnimationFrame(render);

 renderer.clear();

 renderer.render(scene, camera);

 cube.rotation.y += 0.01;

 ctx = canvas.getContext('2d')

 bgcolor = ctx.createLinearGradient(0, 0, 0, pmheight)

 bgcolor.addColorStop(0, "#ff9a9e")

 bgcolor.addColorStop(1, "#fad0c4")

 ctx.fillStyle = bgcolor

 ctx.fillRect(0, 0, pmwidth, pmheight)

 ctx.drawImage(canvasa, 0, 0)

}

render();