function calcRollingFriction(body0, body1, frictionPosWorld, frictionDirectionWorld, maxImpulse) {
    var j1 = 0;
    var contactPosWorld = frictionPosWorld;

    // var rel_pos1 = new Vec3();
    // var rel_pos2 = new Vec3();
    var vel1 = calcRollingFriction_vel1;
    var vel2 = calcRollingFriction_vel2;
    var vel = calcRollingFriction_vel;
    // contactPosWorld.vsub(body0.position, rel_pos1);
    // contactPosWorld.vsub(body1.position, rel_pos2);

    body0.getVelocityAtWorldPoint(contactPosWorld, vel1);
    body1.getVelocityAtWorldPoint(contactPosWorld, vel2);
    vel1.vsub(vel2, vel);

    var vrel = frictionDirectionWorld.dot(vel);

    var denom0 = computeImpulseDenominator(body0, frictionPosWorld, frictionDirectionWorld);
    var denom1 = computeImpulseDenominator(body1, frictionPosWorld, frictionDirectionWorld);
    var relaxation = 1;
    var jacDiagABInv = relaxation / (denom0 + denom1);

    // calculate j that moves us to zero relative velocity
    j1 = -vrel * jacDiagABInv;

    if (maxImpulse < j1) {
        j1 = maxImpulse;
    }
    if (j1 < -maxImpulse) {
        j1 = -maxImpulse;
    }

    return j1;
}
Get the world transform of one of the wheels
@method getWheelTransformWorld
@param  {integer} wheelIndex
@return {Transform}