function rain() {
	
	this.isInit = false;
	this.MASS = 0.9;
	
    this.init = function() {
	
		// modify lighting
		this.HSL = light.color.getHSL();
		light.color.setHSL(this.HSL.h, this.HSL.s, 0.2);
	
		if(this.isInit === true) return;
	
		// create the particle variables
		this.particleCount = 8000,
		this.particles = new THREE.Geometry(),
		this.pMaterial = new THREE.ParticleBasicMaterial({
			color: 0xFFFFFF,
			size: 15,
			map: THREE.ImageUtils.loadTexture(
				"./images/raindrop.png"
			),
			blending: THREE.AdditiveBlending,
			transparent: true,
			opacity: 1
		});

        // now create the individual particles
        for (var p = 0; p < this.particleCount; p++) {

            // create a particle with random
            // position values, -250 -> 250
			var pX = (Math.random() * 10000) - 5000,
				pY = Math.random() * window.innerHeight * 6 - window.innerHeight,
				pZ = (Math.random() * 10000) - 5000;
				this.particle = new THREE.Vector3(pX, pY, pZ);	

            // create a velocity vector
			this.particle.velocity = new THREE.Vector3(
				(windForce.x * this.MASS), 	// x
				-Math.random() * this.MASS, // y
				(windForce.z * this.MASS) 	// z
			); 

            // add it to the geometry
            this.particles.vertices.push(this.particle);
        }

        // create the particle system
        this.particleSystem = new THREE.ParticleSystem(
            this.particles,
            this.pMaterial);

        this.particleSystem.sortParticles = true;
		this.isInit = true;
    }

	this.system = function(){
		return this.particleSystem;
	}

    this.update = function() {

		// add some rotation to the system
		//particleSystem.rotation.y += 0.01;
		
		var pCount = this.particleCount;
		while(pCount--) {
			// get the particle
			this.particle = this.particles.vertices[pCount];
			
			// check if we need to reset
			if(this.particle.y < -10) {
				this.particle.y = (window.innerHeight*6)+(Math.random() * 100);
				this.particle.velocity.y = 0;
				this.particle.x = (Math.random() * 10000) - 5000;
				this.particle.z = (Math.random() * 10000) - 5000;
			}
			
			// update the velocity
			this.particle.velocity.y -= Math.random() * 0.01;
			this.particle.velocity.x = windForce.x * (1-this.MASS);
			this.particle.velocity.z = windForce.z * (1-this.MASS)
			
			// and the position
			this.particle.addVectors( 
				this.particle,
				this.particle.velocity);
		}
		
		// flag to the particle system that we've
		// changed its vertices.
		this.particleSystem.geometry.__dirtyVertices = true;
    }
	
}