/* ContactPointAdd, ContactPointRemove, ContactPointPersist */
        public override function PreSolve(contact:b2Contact, oldManifold:b2Manifold):void
        {
            var u1:ShapeUserData = contact.GetFixtureA().GetUserData();
            var u2:ShapeUserData = contact.GetFixtureB().GetUserData();
            if (u1 == null || u2 == null) return;

            var cr:int = rdPtr.collReg[u1.collType][u2.collType] | rdPtr.collReg[u2.collType][u1.collType];
            cr &= 0xff; //char cr;

            if (cr == 1)
            {
                /* Prepare collision data global to all points */
                var collData:CollData = new CollData();
                collData.body1 = u1.body;
                collData.body2 = u2.body;
                collData.collPoint.SetZero();
                collData.shape1 = u1.ID;
                collData.shape2 = u2.ID;
                collData.type1 = u1.collType;
                collData.type2 = u2.collType;

                /* Get world manifold (so we can convert local to global contact points) */
                var worldManifold:b2WorldManifold = new b2WorldManifold();
                contact.GetWorldManifold(worldManifold);

                /* Find differences between the two manifold point vectors */
                var newPoints:Vector.<b2ManifoldPoint> = contact.GetManifold().m_points;
                var oldPoints:Vector.<b2ManifoldPoint> = oldManifold.m_points;

                /* Find new or old points */
                var point:b2ManifoldPoint;
                var c:CollideCallback;
                var i:int = 0;

                for each(point in newPoints)
                {
                    /* ContactPointAdd */
                    if(!findPoint(oldPoints, point))
                    {
                        c = new CollideCallback(21);
                        c.data = collData.clone();
                        /* Collision point = average of global for both bodies of manifold local point */

                        trace(newPoints.length, worldManifold.m_points.length);

                        c.data.collPoint = worldManifold.m_points[i];
                        c.data.collPoint.Multiply(rdPtr.scale);
                        /* TODO copy velocity etc. */
                        if(c.data.collPoint.x != 0 && c.data.collPoint.y != 0)
                            rdPtr.addCallback(c);
                    }
                    /* ContactPointPersist */
                    else
                    {
                        c = new CollideCallback(24);
                        c.data = collData.clone();
                        c.data.collPoint = point.m_localPoint;
                        /* TODO copy velocity etc. */
                        rdPtr.addCallback(c);
                    }

                    /* Keep track of wolrd point */
                    ++i;
                }

                /* Find removed points */
                for each(point in oldPoints)
                {
                    /* ContactPointRemove */
                    if(!findPoint(newPoints, point))
                    {
                        c = new CollideCallback(27);
                        c.data = collData.clone();
                        c.data.collPoint = point.m_localPoint;
                        /* TODO copy velocity etc. */
                        rdPtr.addCallback(c);
                    }
                }
            }
        }