Three.js - Camera collision with scene - three.js

Question

This is my first question in StackOverflow, but I've been browsing it for some years now, so I kindly ask you to bear with me. :)
I've been experimenting with Three.js to create a 3D world, and everything looked fine until I needed to control the camera. Since I'm using this lib to avoid having to do matricial calculations myself I found and added TrackballControls to my code aswell. It worked fine but then my camera could pass through the 3D shapes, and also below terrain. Unfortunately, although the movement is exactly what I needed, it didn't serve the purpose of allowing camera to respect collision.
My scene is simply the ground (thin BoxGeometry) and a cube (normal-sized BoxGeometry), and a rotating sphere that shares directionalLight position for a "sun light" effect. Some people here suggested adding Physijs to the code and simulate() physics within the scene, and adding a BoxMesh to the camera to make the physics apply to it aswell, but it simply didn't work (scene turned blank).
My working code so far (without Physijs) is:
window.onload = function() {
var renderer, scene, camera, ground, box, sphere, ambient_light, sun_light, controls;
var angle = 0;
var clock = new THREE.Clock();
init();
render();
function init(){
// Create renderer and add it to the page
renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize( window.innerWidth, window.innerHeight );
renderer.setClearColor( 0xffffff );
renderer.shadowMapEnabled = true;
document.body.appendChild( renderer.domElement );
// Create a scene to hold our awesome 3D world
scene = new THREE.Scene();
/*** 3D WORLD ***/
// Objects
ground = new THREE.Mesh(
new THREE.BoxGeometry(50, 1, 50),
new THREE.MeshLambertMaterial({ color: 0x33CC33 }),
0 // mass
);
ground.receiveShadow = true;
scene.add( ground );
box = new THREE.Mesh(
new THREE.BoxGeometry( 10, 10, 10 ),
new THREE.MeshLambertMaterial({ color: 0xDD3344 })
);
box.position.y = 5;
box.castShadow = true;
scene.add( box );
sphere = new THREE.Mesh(
new THREE.SphereGeometry( 3, 32, 32 ),
new THREE.MeshBasicMaterial({ color: 0xFFBB00 })
);
sphere.position.set( 1, 15.5, 5 );
scene.add( sphere );
// Light
ambient_light = new THREE.AmbientLight( 0x333333 );
ambient_light.mass = 0;
scene.add( ambient_light );
sun_light = new THREE.DirectionalLight( 0xBBBBBB );
sun_light.position.set( 1, 15.5, 5 );
sun_light.castShadow = true;
sun_light.shadowCameraNear = 1;
sun_light.shadowCameraFar = 100;
sun_light.shadowCameraLeft = -50;
sun_light.shadowCameraRight = 50;
sun_light.shadowCameraTop = -50;
sun_light.shadowCameraBottom = 50;
sun_light.shadowBias = -.01;
scene.add( sun_light );
// Create a camera
camera = new THREE.PerspectiveCamera(
45, // FOV
window.innerWidth / window.innerHeight, // Aspect Ratio
1, // Near plane
1000 // Far plane
);
camera.position.set( 30, 30, 30 ); // Position camera
camera.lookAt( box.position ); // Look at the scene origin
scene.add(camera);
// After swapping THREE.Mesh to Physijs.BoxMesh, this is where I'd attach a BoxMesh to the camera
window.addEventListener( 'resize', onWindowResize, false );
controls = new THREE.TrackballControls( camera );
controls.rotateSpeed = 4.0;
controls.panSpeed = 0.3;
controls.staticMoving = true; // No sliding after-effects
}
function render() {
// use requestAnimationFrame to create a render loop
angle += .007;
var oscillateZ = Math.sin(angle * (Math.PI*4));
var oscillateX = -Math.cos(angle * (Math.PI*4));
//console.log(oscillateZ);
sphere.position.setZ( sphere.position.z + oscillateZ );
sphere.position.setX( sphere.position.x + oscillateX );
sun_light.position.setZ( sun_light.position.z + oscillateZ );
sun_light.position.setX( sun_light.position.x + oscillateX );
requestAnimationFrame( render );
controls.update();
renderer.render( scene, camera );
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize( window.innerWidth, window.innerHeight );
}
};
Can you guys enlighten me? Thank you for your time!
#Edit
Physijs attempt