From 5e0c284f3a8debdd9ebb080f80e36dceb7bc4ce2 Mon Sep 17 00:00:00 2001
From: Perttu Ahola <celeron55@gmail.com>
Date: Wed, 1 Dec 2010 15:20:12 +0200
Subject: [PATCH] some work-in-progress water stuff

---
 Makefile      |   4 +-
 src/main.cpp  | 194 +++++++++++++++++++++++++++++++++++
 src/mapnode.h |  22 +---
 src/test.cpp  |  55 ++++++++--
 src/voxel.cpp | 278 +++++++++++++++++++++++++++++++++-----------------
 src/voxel.h   | 119 +++++++++++++++------
 6 files changed, 517 insertions(+), 155 deletions(-)

diff --git a/Makefile b/Makefile
index 2b4e8dda3..102a3dcdb 100644
--- a/Makefile
+++ b/Makefile
@@ -13,9 +13,9 @@ JTHREADPATH = ../jthread/jthread-1.2.1
 CPPFLAGS = -I$(IRRLICHTPATH)/include -I/usr/X11R6/include -I$(JTHREADPATH)/src
 
 #CXXFLAGS = -O2 -ffast-math -Wall -fomit-frame-pointer -pipe
-CXXFLAGS = -O2 -ffast-math -Wall -g -pipe
+#CXXFLAGS = -O2 -ffast-math -Wall -g -pipe
 #CXXFLAGS = -O1 -ffast-math -Wall -g
-#CXXFLAGS = -Wall -g -O0
+CXXFLAGS = -Wall -g -O0
 
 #CXXFLAGS = -O3 -ffast-math -Wall
 #CXXFLAGS = -O3 -ffast-math -Wall -g
diff --git a/src/main.cpp b/src/main.cpp
index 677f03843..938eb14ef 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -81,6 +81,9 @@ SUGGESTION: Use same technique for sector heightmaps as what we're
             using for UnlimitedHeightmap? (getting all neighbors
 			when generating)
 
+TODO: Proper handling of spawning place (try to find something that
+      is not in the middle of an ocean (some land to stand on at
+	  least) and save it in map config.
 SUGG: Set server to automatically find a good spawning place in some
       place where there is water and land.
 	  - Map to have a getWalkableNear(p)
@@ -176,6 +179,197 @@ TODO: MovingObject::move and Player::move are basically the same.
 Doing now:
 ======================================================================
 
+Water dynamics pseudo-code (block = MapNode):
+SUGG: Create separate flag table in VoxelManipulator to allow fast
+clearing of "modified" flags
+
+neighborCausedPressure(pos):
+	pressure = 0
+	dirs = {down, left, right, back, front, up}
+	for d in dirs:
+		pos2 = pos + d
+		p = block_at(pos2).pressure
+		if d.Y == 1 and p > min:
+			p -= 1
+		if d.Y == -1 and p < max:
+			p += 1
+		if p > pressure:
+			pressure = p
+	return pressure
+
+# This should somehow update all changed pressure values
+# in an unknown body of water
+updateWaterPressure(pos):
+	TODO
+
+FIXME: This goes in an indefinite loop when there is an underwater
+chamber like this:
+
+#111######
+#222##22##
+#33333333x<- block removed from here
+##########
+
+#111######
+#222##22##
+#3333333x1
+##########
+
+#111######
+#222##22##
+#333333x11
+##########
+
+#111######
+#222##2x##
+#333333333
+##########
+
+#111######
+#222##x2##
+#333333333
+##########
+
+Now, consider moving to the last block not allowed.
+
+Consider it a 3D case with a depth of 2. We're now at this situation.
+Note the additional blocking ## in the second depth plane.
+
+z=1         z=2
+#111######  #111######
+#222##x2##  #222##22##
+#333333333  #33333##33
+##########  ##########
+
+#111######  #111######
+#222##22##  #222##x2##
+#333333333  #33333##33
+##########  ##########
+
+#111######  #111######
+#222##22##  #222##2x##
+#333333333  #33333##33  
+##########  ##########
+
+Now there is nowhere to go, without going to an already visited block,
+but the pressure calculated in here from neighboring blocks is >= 2,
+so it is not the final ending.
+
+We will back up to a state where there is somewhere to go to.
+It is this state:
+
+#111######  #111######
+#222##22##  #222##22##
+#333333x33  #33333##33
+##########  ##########
+
+Then just go on, avoiding already visited blocks:
+
+#111######  #111######
+#222##22##  #222##22##
+#33333x333  #33333##33
+##########  ##########
+
+#111######  #111######
+#222##22##  #222##22##
+#3333x3333  #33333##33
+##########  ##########
+
+#111######  #111######
+#222##22##  #222##22##
+#333x33333  #33333##33
+##########  ##########
+
+#111######  #111######
+#222##22##  #222##22##
+#33x333333  #33333##33
+##########  ##########
+
+#111######  #111######
+#22x##22##  #222##22##
+#333333333  #33333##33
+##########  ##########
+
+#11x######  #111######
+#222##22##  #222##22##
+#333333333  #33333##33
+##########  ##########
+
+"Blob". the air bubble finally got out of the water.
+Then return recursively to a state where there is air next to water,
+clear the visit flags and feed the neighbor of the water recursively
+to the algorithm.
+
+#11 ######  #111######
+#222##22##  #222##22##
+#333333333x #33333##33
+##########  ##########
+
+#11 ######  #111######
+#222##22##  #222##22##
+#33333333x3 #33333##33
+##########  ##########
+
+...and so on.
+
+
+# removed_pos: a position that has been changed from something to air
+flowWater(removed_pos):
+	dirs = {top, left, right, back, front, bottom}
+	selected_dir = None
+	for d in dirs:
+		b2 = removed_pos + d
+
+		# Ignore positions that don't have water
+		if block_at(b2) != water:
+			continue
+
+		# Ignore positions that have already been checked
+		if block_at(b2).checked:
+			continue
+
+		# If block is at top, select it always.
+		if d.Y == 1:
+			selected_dir = d
+			break
+
+		# If block is at bottom, select it if it has enough pressure.
+		# >= 3 needed for stability (and sanity)
+		if d.Y == -1:
+			if block_at(b2).pressure >= 3:
+				selected_dir = d
+				break
+			continue
+		
+		# Else block is at some side. select it if it has enough pressure.
+		if block_at(b2).pressure >= 2:
+			selected_dir = d
+			break
+	
+	# If there is nothing to do anymore, return.
+	if selected_dir == None
+		return
+	
+	b2 = removed_pos + selected_dir
+	
+	# Move block
+	set_block(removed_pos, block_at(b2))
+	set_block(b2, air_block)
+	
+	# Update pressure
+	updateWaterPressure(removed_pos)
+	
+	# Flow water to the newly created empty position
+	flowWater(b2)
+
+	# Check empty positions around and try flowing water to them
+	for d in dirs:
+		b3 = removed_pos + d
+		# Ignore positions that are not air
+		if block_at(b3) is not air:
+			continue
+		flowWater(b3)
+
 
 ======================================================================
 
diff --git a/src/mapnode.h b/src/mapnode.h
index 789cedb27..02abe4e52 100644
--- a/src/mapnode.h
+++ b/src/mapnode.h
@@ -35,9 +35,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 /*
 	Ignored node.
 
-	param is used for custom information in special containers,
-	like VoxelManipulator.
-
 	Anything that stores MapNodes doesn't have to preserve parameters
 	associated with this material.
 	
@@ -67,27 +64,12 @@ enum Material
 
 	MATERIAL_GRASS,
 
-	/*
-		For water, the param is water pressure. 0...127.
-		TODO: No, at least the lowest nibble is used for lighting.
-		
-		- Water will be a bit like light, but with different flow
-		  behavior.
-		- Water blocks will fall down if there is empty space below.
-		- If there is water below, the pressure of the block below is
-		  the pressure of the current block + 1, or higher.
-		- If there is any pressure in a horizontally neighboring
-		  block, a water block will try to move away from it.
-		- If there is >=2 of pressure in a block below, water will
-		  try to move upwards.
-		- NOTE: To keep large operations fast, we have to keep a
-		        cache of the water-air-surfaces, just like with light
-	*/
 	MATERIAL_WATER,
 
 	MATERIAL_LIGHT,
 
 	MATERIAL_TREE,
+	
 	MATERIAL_LEAVES,
 
 	MATERIAL_GRASS_FOOTSTEPS,
@@ -216,6 +198,8 @@ struct MapNode
 	*/
 	s8 param;
 
+	u8 pressure;
+
 	MapNode(const MapNode & n)
 	{
 		*this = n;
diff --git a/src/test.cpp b/src/test.cpp
index 005db2d24..6b285e3a4 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -157,17 +157,16 @@ struct TestVoxelManipulator
 		v.print(dstream);
 
 		dstream<<"*** Setting (-1,0,-1)=2 ***"<<std::endl;
-
-		//v[v3s16(-1,0,-1)] = MapNode(2);
-		v[v3s16(-1,0,-1)].d = 2;
+		
+		v.setNodeNoRef(v3s16(-1,0,-1), MapNode(2));
 
 		v.print(dstream);
 
- 		assert(v[v3s16(-1,0,-1)].d == 2);
+ 		assert(v.getNode(v3s16(-1,0,-1)).d == 2);
 
 		dstream<<"*** Reading from inexistent (0,0,-1) ***"<<std::endl;
 
-		assert(v[v3s16(0,0,-1)].d == MATERIAL_IGNORE);
+		EXCEPTION_CHECK(InvalidPositionException, v.getNode(v3s16(0,0,-1)));
 
 		v.print(dstream);
 
@@ -177,9 +176,51 @@ struct TestVoxelManipulator
 		
 		v.print(dstream);
 
-		assert(v[v3s16(-1,0,-1)].d == 2);
-		assert(v[v3s16(0,1,1)].d == MATERIAL_IGNORE);
+		assert(v.getNode(v3s16(-1,0,-1)).d == 2);
+		EXCEPTION_CHECK(InvalidPositionException, v.getNode(v3s16(0,1,1)));
+
+		/*
+			Water stuff
+		*/
+
+		v.clear();
+
+		const char *content =
+			"#...######"
+			"#...##..##"
+			"#........ "
+			"##########"
+
+			"#...######"
+			"#...##..##"
+			"#........ "
+			"##########"
+		;
+
+		v3s16 size(10, 4, 2);
 		
+		const char *p = content;
+		for(s16 z=0; z<size.Z; z++)
+		for(s16 y=size.Y-1; y>=0; y--)
+		for(s16 x=0; x<size.X; x++)
+		{
+			MapNode n;
+			n.pressure = size.Y - y;
+			if(*p == '#')
+				n.d = MATERIAL_STONE;
+			else if(*p == '.')
+				n.d = MATERIAL_WATER;
+			else if(*p == ' ')
+				n.d = MATERIAL_AIR;
+			else
+				assert(0);
+			v.setNode(v3s16(x,y,z), n);
+			p++;
+		}
+
+		v.print(dstream);
+		
+		//assert(0);
 	}
 };
 
diff --git a/src/voxel.cpp b/src/voxel.cpp
index fc3b4c428..fe176a27a 100644
--- a/src/voxel.cpp
+++ b/src/voxel.cpp
@@ -21,36 +21,98 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "map.h"
 
 VoxelManipulator::VoxelManipulator():
-	m_data(NULL)
+	m_data(NULL),
+	m_flags(NULL)
 {
 }
 
 VoxelManipulator::~VoxelManipulator()
 {
+	clear();
 	if(m_data)
 		delete[] m_data;
+	if(m_flags)
+		delete[] m_flags;
+}
+
+void VoxelManipulator::clear()
+{
+	// Reset area to volume=0
+	m_area = VoxelArea();
+	if(m_data)
+		delete[] m_data;
+	m_data = NULL;
+	if(m_flags)
+		delete[] m_flags;
+	m_flags = NULL;
+}
+
+void VoxelManipulator::print(std::ostream &o)
+{
+	v3s16 em = m_area.getExtent();
+	v3s16 of = m_area.MinEdge;
+	o<<"size: "<<em.X<<"x"<<em.Y<<"x"<<em.Z
+	 <<" offset: ("<<of.X<<","<<of.Y<<","<<of.Z<<")"<<std::endl;
+	
+	for(s32 y=m_area.MaxEdge.Y; y>=m_area.MinEdge.Y; y--)
+	{
+		if(em.X >= 3 && em.Y >= 3)
+		{
+			if     (y==m_area.MinEdge.Y+2) o<<"^     ";
+			else if(y==m_area.MinEdge.Y+1) o<<"|     ";
+			else if(y==m_area.MinEdge.Y+0) o<<"y x-> ";
+			else                           o<<"      ";
+		}
+
+		for(s32 z=m_area.MinEdge.Z; z<=m_area.MaxEdge.Z; z++)
+		{
+			for(s32 x=m_area.MinEdge.X; x<=m_area.MaxEdge.X; x++)
+			{
+				u8 f = m_flags[m_area.index(x,y,z)];
+				char c;
+				if(f & VOXELFLAG_NOT_LOADED)
+					c = 'N';
+				else if(f & VOXELFLAG_INEXISTENT)
+					c = 'I';
+				else
+				{
+					c = 'X';
+					u8 m = m_data[m_area.index(x,y,z)].d;
+					if(m <= 9)
+						c = m + '0';
+				}
+				o<<c;
+			}
+			o<<' ';
+		}
+		o<<std::endl;
+	}
 }
 
 void VoxelManipulator::addArea(VoxelArea area)
 {
+	// Cancel if requested area has zero volume
 	if(area.getExtent() == v3s16(0,0,0))
 		return;
 	
+	// Cancel if m_area already contains the requested area
+	if(m_area.contains(area))
+		return;
+	
 	// Calculate new area
 	VoxelArea new_area;
+	// New area is the requested area if m_area has zero volume
 	if(m_area.getExtent() == v3s16(0,0,0))
 	{
 		new_area = area;
 	}
+	// Else add requested area to m_area
 	else
 	{
 		new_area = m_area;
 		new_area.addArea(area);
 	}
 
-	if(new_area == m_area)
-		return;
-
 	s32 new_size = new_area.getVolume();
 
 	/*dstream<<"adding area ";
@@ -63,11 +125,11 @@ void VoxelManipulator::addArea(VoxelArea area)
 	dstream<<std::endl;*/
 
 	// Allocate and clear new data
-	MapNode *new_data;
-	new_data = new MapNode[new_size];
+	MapNode *new_data = new MapNode[new_size];
+	u8 *new_flags = new u8[new_size];
 	for(s32 i=0; i<new_size; i++)
 	{
-		new_data[i].d = MATERIAL_IGNORE;
+		new_flags[i] = VOXELFLAG_NOT_LOADED;
 	}
 	
 	// Copy old data
@@ -76,48 +138,31 @@ void VoxelManipulator::addArea(VoxelArea area)
 	for(s32 y=m_area.MinEdge.Y; y<=m_area.MaxEdge.Y; y++)
 	for(s32 x=m_area.MinEdge.X; x<=m_area.MaxEdge.X; x++)
 	{
-		new_data[new_area.index(z,y,x)] = m_data[m_area.index(x,y,z)];
+		// If loaded, copy data and flags
+		if((m_flags[m_area.index(x,y,z)] & VOXELFLAG_NOT_LOADED) == false)
+		{
+			new_data[new_area.index(x,y,z)] = m_data[m_area.index(x,y,z)];
+			new_flags[new_area.index(x,y,z)] = m_flags[m_area.index(x,y,z)];
+		}
 	}
 
-	// Replace member
-	m_area = new_area;
-	MapNode *old_data = m_data;
-	m_data = new_data;
-	delete[] old_data;
-}
-
-void VoxelManipulator::print(std::ostream &o)
-{
-	v3s16 em = m_area.getExtent();
-	v3s16 of = m_area.MinEdge;
-	o<<"size: "<<em.X<<"x"<<em.Y<<"x"<<em.Z
-	 <<" offset: ("<<of.X<<","<<of.Y<<","<<of.Z<<")"<<std::endl;
+	// Replace area, data and flags
 	
-	for(s32 y=m_area.MinEdge.Y; y<=m_area.MaxEdge.Y; y++)
-	{
-		if(em.X >= 3 && em.Y >= 3)
-		{
-			if(y==m_area.MinEdge.Y+0) o<<"y x-> ";
-			if(y==m_area.MinEdge.Y+1) o<<"|     ";
-			if(y==m_area.MinEdge.Y+2) o<<"V     ";
-		}
+	m_area = new_area;
+	
+	MapNode *old_data = m_data;
+	u8 *old_flags = m_flags;
 
-		for(s32 z=m_area.MinEdge.Z; z<=m_area.MaxEdge.Z; z++)
-		{
-			for(s32 x=m_area.MinEdge.X; x<=m_area.MaxEdge.X; x++)
-			{
-				u8 m = m_data[m_area.index(x,y,z)].d;
-				char c = 'X';
-				if(m == MATERIAL_IGNORE)
-					c = 'I';
-				else if(m <= 9)
-					c = m + '0';
-				o<<c;
-			}
-			o<<' ';
-		}
-		o<<std::endl;
-	}
+	/*dstream<<"old_data="<<(int)old_data<<", new_data="<<(int)new_data
+	<<", old_flags="<<(int)m_flags<<", new_flags="<<(int)new_flags<<std::endl;*/
+
+	m_data = new_data;
+	m_flags = new_flags;
+	
+	if(old_data)
+		delete[] old_data;
+	if(old_flags)
+		delete[] old_flags;
 }
 
 void VoxelManipulator::interpolate(VoxelArea area)
@@ -156,10 +201,13 @@ void VoxelManipulator::interpolate(VoxelArea area)
 		{
 			v3s16 p2 = p + dirs[i];
 
-			MapNode &n = m_data[m_area.index(p2)];
-			if(n.d == MATERIAL_IGNORE)
+			u8 f = m_flags[m_area.index(p2)];
+			assert(!(f & VOXELFLAG_NOT_LOADED));
+			if(f & VOXELFLAG_INEXISTENT)
 				continue;
 
+			MapNode &n = m_data[m_area.index(p2)];
+
 			airness += (n.d == MATERIAL_AIR) ? 1 : -1;
 			total++;
 
@@ -182,57 +230,91 @@ void VoxelManipulator::interpolate(VoxelArea area)
 	}
 }
 
-#if 0
-void VoxelManipulator::blitFromNodeContainer
-		(v3s16 p_from, v3s16 p_to, v3s16 size, NodeContainer *c)
+void VoxelManipulator::flowWater(v3s16 removed_pos)
 {
-	VoxelArea a_to(p_to, p_to+size-v3s16(1,1,1));
-	addArea(a_to);
-	for(s16 z=0; z<size.Z; z++)
-	for(s16 y=0; y<size.Y; y++)
-	for(s16 x=0; x<size.X; x++)
-	{
-		v3s16 p(x,y,z);
-		try{
-			MapNode n = c->getNode(p_from + p);
-			m_data[m_area.index(p_to + p)] = n;
-		}
-		catch(InvalidPositionException &e)
-		{
-		}
-		
-		/*v3s16 p(x,y,z);
-		MapNode n(MATERIAL_IGNORE);
-		try{
-			n = c->getNode(p_from + p);
-		}
-		catch(InvalidPositionException &e)
-		{
-		}
-		m_data[m_area.index(p_to + p)] = n;*/
-	}
-}
+	v3s16 dirs[6] = {
+		v3s16(0,1,0), // top
+		v3s16(-1,0,0), // left
+		v3s16(1,0,0), // right
+		v3s16(0,0,-1), // front
+		v3s16(0,0,1), // back
+		v3s16(0,-1,0), // bottom
+	};
 
-void VoxelManipulator::blitToNodeContainer
-		(v3s16 p_from, v3s16 p_to, v3s16 size, NodeContainer *c)
-{
-	for(s16 z=0; z<size.Z; z++)
-	for(s16 y=0; y<size.Y; y++)
-	for(s16 x=0; x<size.X; x++)
+	v3s16 p;
+
+	// Load neighboring nodes
+	// TODO: A bigger area would be better
+	emerge(VoxelArea(removed_pos - v3s16(1,1,1), removed_pos + v3s16(1,1,1)));
+
+	s32 i;
+	for(i=0; i<6; i++)
 	{
-		v3s16 p(x,y,z);
-		try{
-			MapNode &n = m_data[m_area.index(p_from + p)];
-			if(n.d == MATERIAL_IGNORE)
-				continue;
-			c->setNode(p_to + p, n);
-		}
-		catch(InvalidPositionException &e)
+		p = removed_pos + dirs[i];
+		u8 f = m_flags[m_area.index(p)];
+		// Inexistent or checked nodes can't move
+		if(f & (VOXELFLAG_INEXISTENT | VOXELFLAG_CHECKED))
+			continue;
+		MapNode &n = m_data[m_area.index(p)];
+		// Only liquid nodes can move
+		if(material_liquid(n.d) == false)
+			continue;
+		// If block is at top, select it always
+		if(i == 0)
 		{
+			break;
+		}
+		// If block is at bottom, select it if it has enough pressure
+		if(i == 5)
+		{
+			if(n.pressure >= 3)
+				break;
+			continue;
+		}
+		// Else block is at some side. Select it if it has enough pressure
+		if(n.pressure >= 2)
+		{
+			break;
 		}
 	}
+
+	// If there is nothing to move, return
+	if(i==6)
+		return;
+	
+	// Switch nodes at p and removed_pos
+	MapNode n = m_data[m_area.index(p)];
+	u8 f = m_flags[m_area.index(p)];
+	m_data[m_area.index(p)] = m_data[m_area.index(removed_pos)];
+	m_flags[m_area.index(p)] = m_flags[m_area.index(removed_pos)];
+	m_data[m_area.index(removed_pos)] = n;
+	m_flags[m_area.index(removed_pos)] = f;
+
+	// Mark p checked
+	m_flags[m_area.index(p)] |= VOXELFLAG_CHECKED;
+	
+	// Update pressure
+	//TODO
+
+	// Flow water to the newly created empty position
+	flowWater(p);
+	
+	// Try flowing water to empty positions around removed_pos.
+	// They are checked in reverse order compared to the previous loop.
+	for(i=5; i>=0; i--)
+	{
+		p = removed_pos + dirs[i];
+		u8 f = m_flags[m_area.index(p)];
+		// Water can't move to inexistent nodes
+		if(f & VOXELFLAG_INEXISTENT)
+			continue;
+		MapNode &n = m_data[m_area.index(p)];
+		// Water can only move to air
+		if(n.d != MATERIAL_AIR)
+			continue;
+		flowWater(p);
+	}
 }
-#endif
 
 /*
 	MapVoxelManipulator
@@ -254,12 +336,18 @@ void MapVoxelManipulator::emerge(VoxelArea a)
 	for(s16 x=0; x<size.X; x++)
 	{
 		v3s16 p(x,y,z);
+		s32 i = m_area.index(a.MinEdge + p);
+		// Don't touch nodes that have already been loaded
+		if(!(m_flags[i] & VOXELFLAG_NOT_LOADED))
+			continue;
 		try{
 			MapNode n = m_map->getNode(a.MinEdge + p);
-			m_data[m_area.index(a.MinEdge + p)] = n;
+			m_data[i] = n;
+			m_flags[i] = 0;
 		}
 		catch(InvalidPositionException &e)
 		{
+			m_flags[i] = VOXELFLAG_INEXISTENT;
 		}
 	}
 }
@@ -280,9 +368,11 @@ void MapVoxelManipulator::blitBack
 	{
 		v3s16 p(x,y,z);
 
-		MapNode &n = m_data[m_area.index(p)];
-		if(n.d == MATERIAL_IGNORE)
+		u8 f = m_flags[m_area.index(p)];
+		if(f & (VOXELFLAG_NOT_LOADED|VOXELFLAG_INEXISTENT))
 			continue;
+
+		MapNode &n = m_data[m_area.index(p)];
 			
 		v3s16 blockpos = getNodeBlockPos(p);
 		
diff --git a/src/voxel.h b/src/voxel.h
index 2bc591d2a..3a4dacd49 100644
--- a/src/voxel.h
+++ b/src/voxel.h
@@ -25,7 +25,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <iostream>
 
 /*
-	TODO: A fast voxel manipulator class
+	A fast voxel manipulator class
 
 	Not thread-safe.
 */
@@ -71,16 +71,24 @@ public:
 		if(p.Y > MaxEdge.Y) MaxEdge.Y = p.Y;
 		if(p.Z > MaxEdge.Z) MaxEdge.Z = p.Z;
 	}
-	v3s16 getExtent()
+	v3s16 getExtent() const
 	{
 		return MaxEdge - MinEdge + v3s16(1,1,1);
 	}
-	s32 getVolume()
+	s32 getVolume() const
 	{
 		v3s16 e = getExtent();
 		return (s32)e.X * (s32)e.Y * (s32)e.Z;
 	}
-	bool isInside(v3s16 p)
+	bool contains(VoxelArea &a) const
+	{
+		return(
+			a.MinEdge.X >= MinEdge.X && a.MaxEdge.X <= MaxEdge.X &&
+			a.MinEdge.Y >= MinEdge.Y && a.MaxEdge.Y <= MaxEdge.Y &&
+			a.MinEdge.Z >= MinEdge.Z && a.MaxEdge.Z <= MaxEdge.Z
+		);
+	}
+	bool contains(v3s16 p) const
 	{
 		return(
 			p.X >= MinEdge.X && p.X <= MaxEdge.X &&
@@ -88,7 +96,7 @@ public:
 			p.Z >= MinEdge.Z && p.Z <= MaxEdge.Z
 		);
 	}
-	bool operator==(const VoxelArea &other)
+	bool operator==(const VoxelArea &other) const
 	{
 		return (MinEdge == other.MinEdge
 				&& MaxEdge == other.MaxEdge);
@@ -97,7 +105,7 @@ public:
 	/*
 		Translates position from virtual coordinates to array index
 	*/
-	s32 index(s16 x, s16 y, s16 z)
+	s32 index(s16 x, s16 y, s16 z) const
 	{
 		v3s16 em = getExtent();
 		v3s16 off = MinEdge;
@@ -105,12 +113,12 @@ public:
 		//dstream<<" i("<<x<<","<<y<<","<<z<<")="<<i<<" ";
 		return i;
 	}
-	s32 index(v3s16 p)
+	s32 index(v3s16 p) const
 	{
 		return index(p.X, p.Y, p.Z);
 	}
 
-	void print(std::ostream &o)
+	void print(std::ostream &o) const
 	{
 		o<<"("<<MinEdge.X
 		 <<","<<MinEdge.Y
@@ -126,6 +134,13 @@ public:
 	v3s16 MaxEdge;
 };
 
+// Hasn't been copied from source (emerged)
+#define VOXELFLAG_NOT_LOADED (1<<0)
+// Checked as being inexistent in source
+#define VOXELFLAG_INEXISTENT (1<<1)
+// Algorithm-dependent
+#define VOXELFLAG_CHECKED (1<<2)
+
 class VoxelManipulator : public NodeContainer
 {
 public:
@@ -141,53 +156,77 @@ public:
 	}
 	bool isValidPosition(v3s16 p)
 	{
-		return m_area.isInside(p);
+		emerge(p);
+		return !(m_flags[m_area.index(p)] & VOXELFLAG_INEXISTENT);
 	}
 	// These are a bit slow and shouldn't be used internally
 	MapNode getNode(v3s16 p)
 	{
-		if(isValidPosition(p) == false)
-			emerge(VoxelArea(p));
+		emerge(p);
 
-		MapNode &n = m_data[m_area.index(p)];
-
-		//TODO: Is this the right behaviour?
-		if(n.d == MATERIAL_IGNORE)
+		if(m_flags[m_area.index(p)] & VOXELFLAG_INEXISTENT)
+		{
+			dstream<<"ERROR: VoxelManipulator::getNode(): "
+					<<"p=("<<p.X<<","<<p.Y<<","<<p.Z<<")"
+					<<", index="<<m_area.index(p)
+					<<", flags="<<(int)m_flags[m_area.index(p)]
+					<<" is inexistent"<<std::endl;
 			throw InvalidPositionException
-			("Not returning MATERIAL_IGNORE in VoxelManipulator");
+			("VoxelManipulator: getNode: inexistent");
+		}
 
-		return n;
+		return m_data[m_area.index(p)];
 	}
-	void setNode(v3s16 p, MapNode & n)
+	void setNode(v3s16 p, MapNode &n)
 	{
-		if(isValidPosition(p) == false)
-			emerge(VoxelArea(p));
+		emerge(p);
+		
 		m_data[m_area.index(p)] = n;
+		m_flags[m_area.index(p)] &= ~VOXELFLAG_INEXISTENT;
+		m_flags[m_area.index(p)] &= ~VOXELFLAG_NOT_LOADED;
 	}
-	
-	MapNode & operator[](v3s16 p)
+	void setNodeNoRef(v3s16 p, MapNode n)
+	{
+		setNode(p, n);
+	}
+
+	/*void setExists(VoxelArea a)
+	{
+		emerge(a);
+		for(s32 z=a.MinEdge.Z; z<=a.MaxEdge.Z; z++)
+		for(s32 y=a.MinEdge.Y; y<=a.MaxEdge.Y; y++)
+		for(s32 x=a.MinEdge.X; x<=a.MaxEdge.X; x++)
+		{
+			m_flags[m_area.index(x,y,z)] &= ~VOXELFLAG_INEXISTENT;
+		}
+	}*/
+
+	/*MapNode & operator[](v3s16 p)
 	{
 		//dstream<<"operator[] p=("<<p.X<<","<<p.Y<<","<<p.Z<<")"<<std::endl;
 		if(isValidPosition(p) == false)
 			emerge(VoxelArea(p));
+		
 		return m_data[m_area.index(p)];
-	}
+	}*/
 
 	/*
-		Manipulation of bigger chunks
+		Control
 	*/
+
+	void clear();
 	
 	void print(std::ostream &o);
 	
 	void addArea(VoxelArea area);
 
+	/*
+		Algorithms
+	*/
+
 	void interpolate(VoxelArea area);
 
-	/*void blitFromNodeContainer
-			(v3s16 p_from, v3s16 p_to, v3s16 size, NodeContainer *c);
-	
-	void blitToNodeContainer
-			(v3s16 p_from, v3s16 p_to, v3s16 size, NodeContainer *c);*/
+	void flowWater(v3s16 removed_pos);
 
 	/*
 		Virtual functions
@@ -195,13 +234,25 @@ public:
 	
 	/*
 		Get the contents of the requested area from somewhere.
+		Shall touch only nodes that have VOXELFLAG_NOT_LOADED
+		Shall reset VOXELFLAG_NOT_LOADED
 
-		If not found from source, add as MATERIAL_IGNORE.
+		If not found from source, add with VOXELFLAG_INEXISTENT
 	*/
 	virtual void emerge(VoxelArea a)
 	{
 		//dstream<<"emerge p=("<<p.X<<","<<p.Y<<","<<p.Z<<")"<<std::endl;
 		addArea(a);
+		for(s32 z=a.MinEdge.Z; z<=a.MaxEdge.Z; z++)
+		for(s32 y=a.MinEdge.Y; y<=a.MaxEdge.Y; y++)
+		for(s32 x=a.MinEdge.X; x<=a.MaxEdge.X; x++)
+		{
+			s32 i = m_area.index(x,y,z);
+			// Don't touch nodes that have already been loaded
+			if(!(m_flags[i] & VOXELFLAG_NOT_LOADED))
+				continue;
+			m_flags[i] = VOXELFLAG_INEXISTENT;
+		}
 	}
 
 	/*
@@ -215,12 +266,14 @@ public:
 	*/
 	VoxelArea m_area;
 	/*
-		NULL if data size is 0
+		NULL if data size is 0 (extent (0,0,0))
 		Data is stored as [z*h*w + y*h + x]
-		Special data values:
-			MATERIAL_IGNORE: Unspecified node
 	*/
 	MapNode *m_data;
+	/*
+		Flags of all nodes
+	*/
+	u8 *m_flags;
 private:
 };