diff --git a/lplanes_pool.cpp b/lplanes_pool.cpp
index 66b4032..d06923a 100644
--- a/lplanes_pool.cpp
+++ b/lplanes_pool.cpp
@@ -23,6 +23,7 @@ unsigned int LPlanesPool::Request()
 	if (m_uiCount >= POOL_MAX)
 		return -1;
 
+	// could be done more efficiently .. NYI
 	for (unsigned int n=0; n<POOL_MAX; n++)
 	{
 		if (m_ucTaken[n] == 0)
diff --git a/lplanes_pool.h b/lplanes_pool.h
index 4462ab6..95ad61b 100644
--- a/lplanes_pool.h
+++ b/lplanes_pool.h
@@ -3,6 +3,11 @@
 #include "lvector.h"
 #include "core/math/plane.h"
 
+// The recursive visibility function needs to allocate lists of planes each time a room is traversed.
+// Instead of doing this allocation on the fly we will use a pool which should be much faster and nearer
+// constant time.
+
+// Note this simple pool isn't super optimal but should be fine for now.
 class LPlanesPool
 {
 public:
diff --git a/lroom.cpp b/lroom.cpp
index 33b48d1..9b128d3 100644
--- a/lroom.cpp
+++ b/lroom.cpp
@@ -120,9 +120,18 @@ void LRoom::DetermineVisibility_Recursive(LRoomManager &manager, int depth, cons
 
 	print("DetermineVisibility_Recursive from " + get_name());
 
-	// set the frame counter
+	// only handle one touch per frame so far (one portal into room)
 	assert (manager.m_uiFrameCounter > m_uiFrameTouched);
-	m_uiFrameTouched = manager.m_uiFrameCounter;
+
+	// first touch
+	if (m_uiFrameTouched < manager.m_uiFrameCounter)
+	{
+		// set the frame counter
+		m_uiFrameTouched = manager.m_uiFrameCounter;
+
+		// keep track of which rooms are shown this frame
+		manager.m_pCurr_VisibleRoomList->push_back(m_RoomID);
+	}
 
 	// show this room and add to visible list of rooms
 	GetGodotRoom()->show();
diff --git a/lroom_converter.h b/lroom_converter.h
index 9899a6e..2f8d1d0 100644
--- a/lroom_converter.h
+++ b/lroom_converter.h
@@ -23,12 +23,12 @@ public:
 	}
 	void ExpandToEnclose(const AABB &bb)
 	{
-		if 	(bb.position.x < m_ptMins.x) m_ptMins.x = bb.position.x;
-		if 	(bb.position.y < m_ptMins.y) m_ptMins.y = bb.position.y;
-		if 	(bb.position.z < m_ptMins.z) m_ptMins.z = bb.position.z;
-		if 	(bb.position.x + bb.size.x > m_ptMaxs.x) m_ptMaxs.x = bb.position.x + bb.size.x;
-		if 	(bb.position.y + bb.size.y > m_ptMaxs.y) m_ptMaxs.y = bb.position.y + bb.size.y;
-		if 	(bb.position.z + bb.size.z > m_ptMaxs.z) m_ptMaxs.z = bb.position.z + bb.size.z;
+		if (bb.position.x < m_ptMins.x) m_ptMins.x = bb.position.x;
+		if (bb.position.y < m_ptMins.y) m_ptMins.y = bb.position.y;
+		if (bb.position.z < m_ptMins.z) m_ptMins.z = bb.position.z;
+		if (bb.position.x + bb.size.x > m_ptMaxs.x) m_ptMaxs.x = bb.position.x + bb.size.x;
+		if (bb.position.y + bb.size.y > m_ptMaxs.y) m_ptMaxs.y = bb.position.y + bb.size.y;
+		if (bb.position.z + bb.size.z > m_ptMaxs.z) m_ptMaxs.z = bb.position.z + bb.size.z;
 	}
 	Vector3 FindCentre() const
 	{
diff --git a/lroom_manager.cpp b/lroom_manager.cpp
index 76e3866..50ee101 100644
--- a/lroom_manager.cpp
+++ b/lroom_manager.cpp
@@ -28,6 +28,10 @@ LRoomManager::LRoomManager()
 {
 	m_cameraID = 0;
 	m_uiFrameCounter = 0;
+
+	// to know which rooms to hide we keep track of which were shown this, and the previous frame
+	m_pCurr_VisibleRoomList = &m_VisibleRoomList[0];
+	m_pPrev_VisibleRoomList = &m_VisibleRoomList[1];
 }
 
 int LRoomManager::FindClosestRoom(const Vector3 &pt) const
@@ -226,6 +230,9 @@ void LRoomManager::FrameUpdate()
 	// we keep a frame counter to prevent visiting things multiple times on the same frame in recursive functions
 	m_uiFrameCounter++;
 
+	// clear the visible room list to write to each frame
+	m_pCurr_VisibleRoomList->clear();
+
 	// get the camera desired and make into lcamera
 	Camera * pCamera = 0;
 	if (m_cameraID)
@@ -285,14 +292,35 @@ void LRoomManager::FrameUpdate()
 	pRoom->DetermineVisibility_Recursive(*this, 0, cam, planes);
 
 	// finally hide all the rooms that are currently visible but not in the visible bitfield as having been hit
-	// NOTE this will be done more efficiently, but is okay to start with
-	for (int n=0; n<m_Rooms.size(); n++)
+
+	// to get started
+	if (!m_pPrev_VisibleRoomList->size())
 	{
-		if (!m_BF_visible_rooms.GetBit(n))
+		// NOTE this will be done more efficiently, but is okay to start with
+		for (int n=0; n<m_Rooms.size(); n++)
 		{
-			m_Rooms[n].GetGodotRoom()->hide();
+			if (!m_BF_visible_rooms.GetBit(n))
+			{
+				m_Rooms[n].GetGodotRoom()->hide();
+			}
 		}
 	}
+	else
+	{
+		// hide all rooms that were visible last frame but aren't visible this frame
+		for (int n=0; n<m_pPrev_VisibleRoomList->size(); n++)
+		{
+			int r = (*m_pPrev_VisibleRoomList)[n];
+
+			if (!m_BF_visible_rooms.GetBit(r))
+				m_Rooms[r].GetGodotRoom()->hide();
+		}
+
+		// swap the current and previous visible room list
+		LVector<int> * pTemp = m_pCurr_VisibleRoomList;
+		m_pCurr_VisibleRoomList = m_pPrev_VisibleRoomList;
+		m_pPrev_VisibleRoomList = pTemp;
+	}
 
 	// when running, emit less debugging output so as not to choke the IDE
 	LPortal::m_bRunning = true;
diff --git a/lroom_manager.h b/lroom_manager.h
index c75cf21..2ba594e 100644
--- a/lroom_manager.h
+++ b/lroom_manager.h
@@ -48,8 +48,10 @@ class LRoomManager : public Spatial {
 
 	// keep track of which rooms are visible, so we can hide ones that aren't hit that were previously on
 	Lawn::LBitField_Dynamic m_BF_visible_rooms;
-//	Vector<int> m_VisibleRoomList[2];
-//	int m_CurrentVisibleRoomList;
+	LVector<int> m_VisibleRoomList[2];
+
+	LVector<int> * m_pCurr_VisibleRoomList;
+	LVector<int> * m_pPrev_VisibleRoomList;
 
 	// keep a frame counter, to mark when objects have been hit by the visiblity algorithm
 	// already to prevent multiple hits on rooms and objects