Three.js-Skybox显示黑色

我在Three.js中向简单场景添加skybox时遇到问题！

我用于skybox的代码是：

    var skyBox = new THREE.Mesh( new THREE.BoxGeometry( 1500, 1500, 1500 ), shaderMaterial );
        sceneCube.add( skyBox );

遮光板材料定义如下：

shader = THREE.ShaderLib[ "cube" ];
shader.uniforms[ "tCube" ].value = textureCube;
var shaderMaterial = new THREE.ShaderMaterial( {
    fragmentShader: shader.fragmentShader,
    vertexShader: shader.vertexShader,
    uniforms: shader.uniforms,
    depthWrite: false,
    side: THREE.BackSide
} );

我只想把一些简单的图像显示为Skybox，所以我用它来加载图像：

     var path = "Desert-";
            var format = '.png';
            var urls = [
                path + 'LEFT' + format, path + 'RIGHT' + format,
                path + 'TOP' + format, path + 'BOT' + format,
                path + 'FRONT' + format, path + 'BACK' + format
            ];
            textureCube = new THREE.CubeTextureLoader().load( urls );

运行我的代码不会在web控制台中引发任何错误。作为我使用的基本场景http://threejs.org/examples/#webgl_geometry_cube.

我真的很想在网上找到答案，但我在这里找不到我做错了什么。

谢谢你的帮助！

这里是我使用的完整代码（我发布这篇文章是因为我真的试图应用所有的解决方案，这些解决方案都发布在这里）。

<script>
        var camera, scene, renderer, cameraCube, sceneCube;
        var mesh, shader;
        init();
        animate();
        function init() {
            camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 2000 );
            camera.position.z = 400;
            cameraCube = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 2000 );

            scene = new THREE.Scene();
            sceneCube = new THREE.Scene();

            var path = "textures/Desert-";
            var format = '.png';
            var urls = [
                path + 'LEFT' + format, path + 'RIGHT' + format,
                path + 'TOP' + format, path + 'BOTTOM' + format,
                path + 'FRONT' + format, path + 'BACK' + format
            ];
            console.log(urls);
            textureCube = new THREE.CubeTextureLoader().load( urls );
            // Skybox
            shader = THREE.ShaderLib[ "cube" ];
            shader.uniforms[ "tCube" ].value = textureCube;
            var shaderMaterial = new THREE.ShaderMaterial( {
                fragmentShader: shader.fragmentShader,
                vertexShader: shader.vertexShader,
                uniforms: shader.uniforms,
                depthWrite: false,
                side: THREE.BackSide
            } );

            var skyBox = new THREE.Mesh( new THREE.BoxGeometry( 1500, 1500, 1500 ), shaderMaterial );
            sceneCube.add( skyBox );
            var texture = new THREE.TextureLoader().load( urls[3] );
            var geometry = new THREE.BoxBufferGeometry( 100, 100, 100 );
            var material = new THREE.MeshBasicMaterial( { map: texture } );
            mesh = new THREE.Mesh( geometry, material );
            scene.add( mesh );
            renderer = new THREE.WebGLRenderer();
            renderer.setPixelRatio( window.devicePixelRatio );
            renderer.setSize( window.innerWidth, window.innerHeight );
            document.body.appendChild( renderer.domElement );
            //
            window.addEventListener( 'resize', onWindowResize, false );
        }
        function onWindowResize() {
            camera.aspect = window.innerWidth / window.innerHeight;
            camera.updateProjectionMatrix();

            renderer.setSize( window.innerWidth, window.innerHeight );
        }
        function animate() {
            requestAnimationFrame( animate );
            mesh.rotation.x += 0.005;
            mesh.rotation.y += 0.01;
            renderer.render( sceneCube, cameraCube );
            renderer.render( scene, camera );
        }