public static int GetIslandId(PersistentManifold lhs)
        {
            CollisionObject rcolObj0 = lhs.GetBody0() as CollisionObject;
            int             islandId = rcolObj0.GetIslandTag();

            if (islandId >= 0)
            {
                return(islandId);
            }

            CollisionObject rcolObj1 = lhs.GetBody1() as CollisionObject;

            return(rcolObj1.GetIslandTag());
        }
        public void BuildIslands(IDispatcher dispatcher, CollisionWorld collisionWorld)
        {
            BulletGlobals.StartProfile("islandUnionFindAndQuickSort");

            ObjectArray <CollisionObject> collisionObjects = collisionWorld.GetCollisionObjectArray();

            m_islandmanifold.Clear();

            //we are going to sort the unionfind array, and store the element id in the size
            //afterwards, we clean unionfind, to make sure no-one uses it anymore

            GetUnionFind().sortIslands();
            int numElem = GetUnionFind().GetNumElements();

            int endIslandIndex = 1;


            //update the sleeping state for bodies, if all are sleeping
            for (int startIslandIndex = 0; startIslandIndex < numElem; startIslandIndex = endIslandIndex)
            {
                int islandId = GetUnionFind().GetElement(startIslandIndex).m_id;
#if DEBUG
                if (BulletGlobals.g_streamWriter != null && BulletGlobals.debugIslands)
                {
                    BulletGlobals.g_streamWriter.WriteLine(String.Format("buildIslands start[{0}] end[{1}] id[{2}]", startIslandIndex, endIslandIndex, islandId));
                }
#endif
                for (endIslandIndex = startIslandIndex + 1; (endIslandIndex < numElem) && (GetUnionFind().GetElement(endIslandIndex).m_id == islandId); endIslandIndex++)
                {
                }

                //int numSleeping = 0;

                bool allSleeping = true;

                for (int idx = startIslandIndex; idx < endIslandIndex; idx++)
                {
                    int i = GetUnionFind().GetElement(idx).m_sz;

                    CollisionObject colObj0 = collisionObjects[i];
                    if ((colObj0.GetIslandTag() != islandId) && (colObj0.GetIslandTag() != -1))
                    {
                        //				printf("error in island management\n");
                    }

                    Debug.Assert((colObj0.GetIslandTag() == islandId) || (colObj0.GetIslandTag() == -1));
                    if (colObj0.GetIslandTag() == islandId)
                    {
                        if (colObj0.GetActivationState() == ActivationState.ACTIVE_TAG)
                        {
                            allSleeping = false;
                        }
                        if (colObj0.GetActivationState() == ActivationState.DISABLE_DEACTIVATION)
                        {
                            allSleeping = false;
                        }
                    }
                }


                if (allSleeping)
                {
                    for (int idx = startIslandIndex; idx < endIslandIndex; idx++)
                    {
                        int             i         = GetUnionFind().GetElement(idx).m_sz;
                        CollisionObject colObj0   = collisionObjects[i];
                        int             islandTag = colObj0.GetIslandTag();
                        if (islandTag != islandId && islandTag != -1)
                        {
                            //					printf("error in island management\n");
                        }

                        Debug.Assert((islandTag == islandId) || (islandTag == -1));

                        if (islandTag == islandId)
                        {
                            colObj0.SetActivationState(ActivationState.ISLAND_SLEEPING);
                        }
                    }
                }
                else
                {
                    for (int idx = startIslandIndex; idx < endIslandIndex; idx++)
                    {
                        int i = GetUnionFind().GetElement(idx).m_sz;

                        CollisionObject colObj0   = collisionObjects[i];
                        int             islandTag = colObj0.GetIslandTag();
                        if (islandTag != islandId && islandTag != -1)
                        {
                            //					printf("error in island management\n");
                        }

                        Debug.Assert((islandTag == islandId) || (islandTag == -1));

                        if (islandTag == islandId)
                        {
                            if (colObj0.GetActivationState() == ActivationState.ISLAND_SLEEPING)
                            {
                                colObj0.SetActivationState(ActivationState.WANTS_DEACTIVATION);
                                colObj0.SetDeactivationTime(0f);
                            }
                        }
                    }
                }
            }

            int maxNumManifolds = dispatcher.GetNumManifolds();

            //#definef SPLIT_ISLANDS 1
            //#ifdef SPLIT_ISLANDS


            //#endif //SPLIT_ISLANDS


            for (int i = 0; i < maxNumManifolds; i++)
            {
                PersistentManifold manifold = dispatcher.GetManifoldByIndexInternal(i);

                CollisionObject colObj0 = manifold.GetBody0() as CollisionObject;
                CollisionObject colObj1 = manifold.GetBody1() as CollisionObject;

                ///@todo: check sleeping conditions!
                if (((colObj0 != null) && colObj0.GetActivationState() != ActivationState.ISLAND_SLEEPING) ||
                    ((colObj1 != null) && colObj1.GetActivationState() != ActivationState.ISLAND_SLEEPING))
                {
                    //kinematic objects don't merge islands, but wake up all connected objects
                    if (colObj0.IsKinematicObject() && colObj0.GetActivationState() != ActivationState.ISLAND_SLEEPING)
                    {
                        if (colObj0.HasContactResponse())
                        {
                            colObj1.Activate();
                        }
                    }
                    if (colObj1.IsKinematicObject() && colObj1.GetActivationState() != ActivationState.ISLAND_SLEEPING)
                    {
                        if (colObj1.HasContactResponse())
                        {
                            colObj0.Activate();
                        }
                    }
                    if (m_splitIslands)
                    {
                        //filtering for response
                        if (dispatcher.NeedsResponse(colObj0, colObj1))
                        {
                            m_islandmanifold.Add(manifold);
                        }
                    }
                }
            }
            BulletGlobals.StopProfile();
        }