如何使用Aframe更改.mtl文件中的材质

Question

我正在使用aframe加载.obj和.mtl，一切似乎都很好。但是，我无法更改子节点的材料。有人曾经克服过这个吗？

这是我到目前为止所做的事情

 < a - entity id = "model" position = "0 0 0" 

< a - entity obj - model = "obj: #tree-obj; mtl: #tree-mtl" position = "-.35 
0 .55" rotation = "0 -20 0" scale = "1. 1. 1." > < /a-entity>

< /a-entity>

遍历子项的Java脚本代码

var tex = THREE.ImageUtils.loadTexture( "tex.jpg" );
    var cover = new THREE.MeshPhongMaterial( {
            name:"set2",
            map:tex,
            specular: 0x0f8191,
            emissive: null,
            emissiveIntensity : null,

   } )



  var el = this.el;


         el.object3D.traverse(function( child ) { if (child.material.name == "set2")  {

                                                            child.material = cover;

                                        child.castShadow = true;
                                        child.receiveShadow = true;
                                        child.material.needsUpdate=true;
                            }    
    });

请告诉我我错过的地方。