Weird behaviour of shadows in THREE.js

Question

I am trying to render a set of photos, positioned in 3-dimensional space, which cast shadows on one another. I am starting with two rectangles, and here is my code

function loadScene() {
    var WIDTH = 1200,
        HEIGHT = 500,
        VIEW_ANGLE = 45,
        ASPECT = WIDTH / HEIGHT,
        NEAR = 0.1,
        FAR = 10000,

        world = document.getElementById('world'),
        renderer = new THREE.WebGLRenderer(),
        camera = new THREE.PerspectiveCamera(VIEW_ANGLE, ASPECT, NEAR, FAR),
        scene = new THREE.Scene(),
        texture = THREE.ImageUtils.loadTexture('image.jpg', {}, function() {
            renderer.render(scene, camera);
        }),
        material = new THREE.MeshLambertMaterial({map: texture}),
        solidMaterial = new THREE.MeshPhongMaterial({color: 0xCC0000}),
        rectangle = new THREE.PlaneGeometry(200, 120),
        mesh = new THREE.Mesh(rectangle, material),
        mesh1 = new THREE.Mesh(rectangle, material),
        spotLight = new THREE.SpotLight(0xFFFFFF, 1.3);

    camera.position.set(0, 0, 200);
    mesh.translateX(140);
    mesh.translateZ(-70);
    mesh.receiveShadow = true;
    mesh1.castShadow = true;
    spotLight.position.x = -100;
    spotLight.position.y = 230;
    spotLight.position.z = 230;
    spotLight.castShadow = true;

    scene.add(spotLight);
    scene.add(mesh);
    scene.add(mesh1);
    renderer.setSize(WIDTH, HEIGHT);
    renderer.shadowMapEnabled = true;
    renderer.render(scene, camera);
    world.appendChild(renderer.domElement);
}

Here solidMaterial is a solid red, and material is a textured material. What I get is the following:

• If I use material for both the meshes, the rectangles appear as expected, but without shadows. Same if I use solidMaterial for both.
• If I use material for mesh (the one farther away) and solidMaterial for mesh1, I see a red rectangle which casts shadow on a textured one. This is the only case that works as I would expect.
• If I use solidMaterial for mesh (the one farther away) and material for mesh1, I see a red rectangle with the shadow on it, but the textured rectangle in front is not drawn at all.

What is the correct use of shadows?

Answer 1

It turns out the shadow does not appear when the two rectangles have the same material. I wonder whether this a bug in THREE.js.

On the other hand, if I use two different material, the shadow appears as expected, even if they have the same texture.