function ContactEquation(bodyA, bodyB, maxForce){
    maxForce = typeof(maxForce) !== 'undefined' ? maxForce : 1e6;
    Equation.call(this, bodyA, bodyB, 0, maxForce);

    /**
     * @property restitution
     * @type {Number}
     */
    this.restitution = 0.0; // "bounciness": u1 = -e*u0

    /**
     * World-oriented vector that goes from the center of bi to the contact point.
     * @property {Vec3} ri
     */
    this.ri = new Vec3();

    /**
     * World-oriented vector that starts in body j position and goes to the contact point.
     * @property {Vec3} rj
     */
    this.rj = new Vec3();

    /**
     * Contact normal, pointing out of body i.
     * @property {Vec3} ni
     */
    this.ni = new Vec3();
}
Contact/non-penetration constraint equation
@class ContactEquation
@constructor
@author schteppe
@param {Body} bodyA
@param {Body} bodyB
@extends Equation