function rain() {
	
	this.isInit = false;
	
    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 = 1800,
		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() * window.innerWidth * 2 - window.innerWidth,
                pY = Math.random() * window.innerHeight * 3 - window.innerHeight,
                pZ = Math.random() * window.innerWidth * 2 - window.innerWidth;
                this.particle = new THREE.Vector3(pX, pY, pZ);

            // create a velocity vector
            this.particle.velocity = new THREE.Vector3(
                0, // x
                -Math.random(), // y
                0); // 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 < -200) {
				this.particle.y = Math.random() * window.innerHeight+10;
				this.particle.velocity.y = 0;
			}
			
			// update the velocity
			this.particle.velocity.y -= Math.random() * .1;
			
			// 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;
    }
	
}