Applying different textures on a THREE.js OBJLoader loaded object - three.js

Question

I have a square shape .obj model and 2 textures. How do I apply one texture on it's top face and another on rest of faces?

Answer 1

There are a ton of ways to do what you're asking all with varying complexity depending on your needs. It looks like you want to apply two materials to your object and not two textures.
It looks this way because it seems you want the textures to be interchangeable so there's no way you're going to combine the images and keep resolution and OBJ & THREE.Material only support one set of uv attributes so you can't use a single material and multiple textures. So multiple materials it is...
Multiple materials
If you have two materials (2 THREE.Materials which correlate to 2 WebGL programs) then each face needs to know what material it's assigned to.
While the THREE.js multi material API has been in flux for quite a while and there are differences between THREE.Geometry and THREE.BufferGeometry, fortunately for you THREE.OBJLoader supports material groups out of the box. To get this into THREE.js, you want to apply multiple materials in your 3D editor to your object and then export the OBJ to get everything. Doing it by hand is a little harder and requires calling addGroup as shown in the docs/the link above.
In THREE.js you simply pass in all the materials as an array to your object demonstrated in this answer. I also updated your fiddle to do the same thing. Relevant code shown below
var loadingManager = new THREE.LoadingManager();
var ObjLoader = new THREE.OBJLoader(loadingManager);
var textureLoader = new THREE.TextureLoader(loadingManager);
//Material 1 with first texture
var material = new THREE.MeshLambertMaterial({map: textureLoader.load('https://dl.dropboxusercontent.com/s/nvnacip8fhlrvm4/BoxUV.png?dl=0')});
//Material 2 with second texture
var material2 = new THREE.MeshLambertMaterial({map:
textureLoader.load('https://i.imgur.com/311w7oZ.png')});
ObjLoader.load(
'https://dl.dropboxusercontent.com/s/hiazgei0rxeirr4/cabinet30.obj?dl=0',
function ( object ) {
var geo = object.children[0].geometry;
var mats = [material, material2];
//These are just some random groups to demonstrate multi material, you need to set these up so they actually work for your object, either in code or in your 3D editor
geo.addGroup(0,geo.getAttribute("position").count/2,0);
geo.addGroup(geo.getAttribute("position").count/2,
geo.getAttribute("position").count/2,1);
//Mesh with multiple materials for material parameter
obj = new THREE.Mesh(geo, mats);
obj.position.y = 3;
});