1、線框和mesh同時存在
var wireframeMaterial = new THREE.MeshBasicMaterial( { color: 0x000000, wireframe: true, transparent: true } );
//pn是一個mesh
var wireframe = new THREE.Mesh( pn.geometry, wireframeMaterial );
scene.add( wireframe );
2、只顯示線框
pn.material.wireframe = true;