Change texture of loaded .obj in three.js at runtime

Question

I'm trying to swap image texture at runtime on a loaded three.js .obj. Here's the code straight from three.js examples with slight modification:

        var container, stats;
        var camera, scene, renderer;
        var mouseX = 0, mouseY = 0;
        var windowHalfX = window.innerWidth / 2;
        var windowHalfY = window.innerHeight / 2;


        init();
        animate();


        function init() {

            container = document.createElement( 'div' );
            document.body.appendChild( container );

            camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 2000 );
            camera.position.z = 100;

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

            var ambient = new THREE.AmbientLight( 0x101030 );
            scene.add( ambient );

            var directionalLight = new THREE.DirectionalLight( 0xffeedd );
            directionalLight.position.set( 0, 0, 1 );
            scene.add( directionalLight );

            //manager
            var manager = new THREE.LoadingManager();
            manager.onProgress = function ( item, loaded, total ) {

                console.log( item, loaded, total );

            };

            //model
            var loader = new THREE.OBJLoader( manager );
            loader.load( 'obj/female02/female02.obj', function ( object ) {
                object.traverse( function ( child ) {

                    if ( child instanceof THREE.Mesh ) {
                        //create a global var to reference later when changing textures
                        myMesh = child;
                        //apply texture
                        myMesh.material.map = THREE.ImageUtils.loadTexture( 'textures/ash_uvgrid01.jpg');
                        myMesh.material.needsUpdate = true;
                    }

                } );


                object.position.y = - 80;
                scene.add( object );

            } );

            //render
            renderer = new THREE.WebGLRenderer();
            renderer.setSize( window.innerWidth, window.innerHeight );
            container.appendChild( renderer.domElement );

            document.addEventListener( 'mousemove', onDocumentMouseMove, false );
            window.addEventListener( 'resize', onWindowResize, false );

        }

        function newTexture() {
            myMesh.material.map = THREE.ImageUtils.loadTexture( 'textures/land_ocean_ice_cloud_2048.jpg');
            myMesh.material.needsUpdate = true;
        }

        function onWindowResize() {

            windowHalfX = window.innerWidth / 2;
            windowHalfY = window.innerHeight / 2;

            camera.aspect = window.innerWidth / window.innerHeight;
            camera.updateProjectionMatrix();

            renderer.setSize( window.innerWidth, window.innerHeight );

        }

        function onDocumentMouseMove( event ) {

            mouseX = ( event.clientX - windowHalfX ) / 2;
            mouseY = ( event.clientY - windowHalfY ) / 2;

        }

        //animate
        function animate() {

            requestAnimationFrame( animate );
            render();

        }

        function render() {

            camera.position.x += ( mouseX - camera.position.x ) * .05;
            camera.position.y += ( - mouseY - camera.position.y ) * .05;

            camera.lookAt( scene.position );

            renderer.render( scene, camera );

        }

The only thing I added was the newTexture function and a reference to the mesh as myMesh. Here's the original example (http://threejs.org/examples/webgl_loader_obj.html). The function doesn't throw any errors but the .obj does not update. I know I'm just missing something fundamental here..

Update: Per the excellent answer below, here's the correct code with some additions to swap texture via an input field:

  var container, stats;
  var camera, scene, renderer;
  var mouseX = 0, mouseY = 0;
  var windowHalfX = window.innerWidth / 2;
  var windowHalfY = window.innerHeight / 2;
  var globalObject;

  init();
  animate();

  function init() {
      container = document.createElement('div');
      document.body.appendChild(container);

      camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 1, 2000);
      camera.position.z = 100;

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

      var ambient = new THREE.AmbientLight( 0x101030 );
      scene.add( ambient );

      var directionalLight = new THREE.DirectionalLight( 0xffeedd );
      directionalLight.position.set( 0, 0, 1 );
      scene.add( directionalLight );

      //manager
      var manager = new THREE.LoadingManager();
      manager.onProgress = function (item, loaded, total) {
        console.log( item, loaded, total );
      };

    //model
    var loader = new THREE.OBJLoader( manager );
    loader.load( 'obj/female02/female02.obj', function (object) {
        //store global reference to .obj
        globalObject = object;

      object.traverse( function (child) {
          if ( child instanceof THREE.Mesh ) {
              child.material.map = THREE.ImageUtils.loadTexture( 'textures/grid.jpg');
              child.material.needsUpdate = true;
          }
      });

      object.position.y = - 80;
      scene.add( object );
    });

    //render
    renderer = new THREE.WebGLRenderer();
    renderer.setSize( window.innerWidth, window.innerHeight );
    container.appendChild( renderer.domElement );

    document.addEventListener( 'mousemove', onDocumentMouseMove, false );
    window.addEventListener( 'resize', onWindowResize, false );
  }

  function onWindowResize() {
    windowHalfX = window.innerWidth / 2;
    windowHalfY = window.innerHeight / 2;
    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
    renderer.setSize( window.innerWidth, window.innerHeight );
  }

  function onDocumentMouseMove( event ) {
    mouseX = ( event.clientX - windowHalfX ) / 2;
    mouseY = ( event.clientY - windowHalfY ) / 2;
  }

  //animate
  function animate() {
    requestAnimationFrame( animate );
    render();
  }

  function render() {
    camera.position.x += ( mouseX - camera.position.x ) * .05;
    camera.position.y += ( - mouseY - camera.position.y ) * .05;
            camera.lookAt( scene.position );
            renderer.render( scene, camera );
  }

  function newTexture() {
    var newTexturePath = "textures/" + document.getElementById("texture").value + "";

    globalObject.traverse( function ( child ) {
      if (child instanceof THREE.Mesh) {
          //create a global var to reference later when changing textures
          child;
          //apply texture
          child.material.map = THREE.ImageUtils.loadTexture(newTexturePath);
          child.material.needsUpdate = true;
      }
    });
  }

Answer 1

The problem here is that there are multiple child meshes in the object variable. By having only one myMesh global variable, you are storing only the last child mesh. Thus when you try to update the texture using this global variable, only one of the meshes gets a texture update, probably a small hidden part that is not clearly visible.

The solution would be to either:

• Store a myMeshes array global variable and push myMesh into it every time there is one. Then in your newTexture() function, iterate through all items in this array and update their maps/materials.
• Or, store the object variable (the one returned from OBJLoader's callback) into one single global variable. Then in your newTexture() function, iterate through all the meshes like how it is done in the code (using traverse() and if statement), and update their maps/materials.

Lastly, calling newTexture() somewhere in your code would also help ;)