/**
 * Flade - Flash Dynamics Engine
 * Release 0.4 alpha 
 * RimParticle class
 * Copyright 2004, 2005 Alec Cove
 * 
 * This file is part of Flade. The Flash Dynamics Engine. 
 *	
 * Flade is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Flade is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Flade; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Flash is a registered trademark of Macromedia
 */

/*
 * The RimParticle is really just a second component of the wheel model.
 * The rim particle is simulated in a coordsystem relative to the wheel's 
 * center, not in worldspace
 */
RimParticle = function(r, mt) {
	
	this.curr = new Vector(r, 0);
	this.prev = new Vector(0, 0);
	
	this.vs = 0;			// variable speed
	this.speed = 0; 		// initial speed
	this.maxTorque = mt; 	
	this.wr = r;		
		
}
RimParticle.prototype.depth = 4000;


RimParticle.prototype.verlet = function(sysObj) {

	//clamp torques to valid range
	this.speed = Math.max(-this.maxTorque, Math.min(this.maxTorque, this.speed + this.vs));
	
	//apply torque
	//this is the tangent vector at the rim particle
	var dx = -this.curr.y;
	var dy = this.curr.x;
	
	//normalize so we can scale by the rotational speed
	var len = Math.sqrt(dx * dx + dy * dy);
	dx /= len;
	dy /= len;
	
	this.curr.x += this.speed * dx;
	this.curr.y += this.speed * dy;		

	var ox = this.prev.x;
	var oy = this.prev.y;
	var px = this.prev.x = this.curr.x;		
	var py = this.prev.y = this.curr.y;		
		
	this.curr.x += sysObj.coeffDamp * (px - ox);
	this.curr.y += sysObj.coeffDamp * (py - oy);	

	// hold the rim particle in place
	var clen = Math.sqrt(this.curr.x * this.curr.x + this.curr.y * this.curr.y);
	var diff = (clen - this.wr) / clen;
	
	this.curr.x -= this.curr.x * diff;
	this.curr.y -= this.curr.y * diff;
}