21 files changed, 230 insertions, 125 deletions
diff --git a/source/Blocks/BlockHandler.cpp b/source/Blocks/BlockHandler.cpp
index cde85fce8..71d56f94d 100644
--- a/source/Blocks/BlockHandler.cpp
+++ b/source/Blocks/BlockHandler.cpp
@@ -436,8 +436,8 @@ void cBlockHandler::Check(cWorld * a_World, int a_BlockX, int a_BlockY, int a_Bl
 	}
 	else
 	{
-		// Wake up the simulators:
-		a_World->GetSimulatorManager()->WakeUp(a_BlockX, a_BlockY, a_BlockZ);
+		// Wake up the simulators for this block:
+		a_World->WakeUpSimulators(a_BlockX, a_BlockY, a_BlockZ);
 	}
 }
 
diff --git a/source/Chunk.cpp b/source/Chunk.cpp
index 41cc0e7f6..3616f6b8e 100644
--- a/source/Chunk.cpp
+++ b/source/Chunk.cpp
@@ -492,15 +492,10 @@ void cChunk::BroadcastPendingBlockChanges(void)
 void cChunk::CheckBlocks(void)
 {
 	cCSLock Lock2(m_CSBlockLists);
-	unsigned int NumTickBlocks = m_ToTickBlocks.size();
-	Lock2.Unlock();
-
-	if (NumTickBlocks == 0)
+	if (m_ToTickBlocks.size() == 0)
 	{
 		return;
 	}
-	
-	Lock2.Lock();
 	std::deque< unsigned int > ToTickBlocks = m_ToTickBlocks;
 	m_ToTickBlocks.clear();
 	Lock2.Unlock();
@@ -1131,17 +1126,18 @@ void cChunk::SetBlock( int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType
 	}
 
 	m_ToTickBlocks.push_back(index);
-	CheckNeighbors(a_RelX, a_RelY, a_RelZ);
+	QueueTickBlockNeighbors(a_RelX, a_RelY, a_RelZ);
 
-	Vector3i WorldPos = PositionToWorldPosition( a_RelX, a_RelY, a_RelZ );
-	cBlockEntity* BlockEntity = GetBlockEntity( WorldPos );
-	if( BlockEntity )
+	Vector3i WorldPos = PositionToWorldPosition(a_RelX, a_RelY, a_RelZ);
+	cBlockEntity * BlockEntity = GetBlockEntity(WorldPos);
+	if (BlockEntity != NULL)
 	{
 		BlockEntity->Destroy();
-		RemoveBlockEntity( BlockEntity );
+		RemoveBlockEntity(BlockEntity);
 		delete BlockEntity;
 	}
-	switch( a_BlockType )
+	
+	switch (a_BlockType)
 	{
 		case E_BLOCK_CHEST:
 		{
@@ -1181,76 +1177,52 @@ void cChunk::SetBlock( int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType
 
 
 
-void cChunk::CheckNeighbors(int a_RelX, int a_RelY, int a_RelZ)
+void cChunk::QueueTickBlock(int a_RelX, int a_RelY, int a_RelZ)
 {
-	int BlockX = m_PosX * cChunkDef::Width + a_RelX;
-	int BlockZ = m_PosZ * cChunkDef::Width + a_RelZ;
-	if (a_RelX < cChunkDef::Width - 1)
-	{
-		m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX + 1, a_RelY, a_RelZ));
-	}
-	else
-	{
-		m_ChunkMap->CheckBlock(BlockX + 1, a_RelY, BlockZ);
-	}
-	
-	if (a_RelX > 0)
-	{
-		m_ToTickBlocks.push_back( MakeIndexNoCheck(a_RelX - 1, a_RelY,     a_RelZ));
-	}
-	else
-	{
-		m_ChunkMap->CheckBlock(BlockX - 1, a_RelY, BlockZ);
-	}
-	
-	if (a_RelY < cChunkDef::Height - 1)
-	{
-		m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY + 1, a_RelZ));
-	}
-	
-	if (a_RelY > 0)
-	{
-		m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY - 1, a_RelZ));
-	}
-	
-	if (a_RelZ < cChunkDef::Width - 1)
-	{
-		m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY, a_RelZ + 1));
-	}
-	else
+	if (!IsValid())
 	{
-		m_ChunkMap->CheckBlock(BlockX, a_RelY, BlockZ + 1);
+		return;
 	}
 	
-	if (a_RelZ > 0)
-	{
-		m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY, a_RelZ - 1));
-	}
-	else
-	{
-		m_ChunkMap->CheckBlock(BlockX, a_RelY, BlockZ - 1);
-	}
+	m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY, a_RelZ));
 }
 
 
 
 
 
-void cChunk::CheckBlock(int a_RelX, int a_RelY, int a_RelZ)
+void cChunk::QueueTickBlockNeighbors(int a_RelX, int a_RelY, int a_RelZ)
 {
-	if (!IsValid())
+	int BlockX = m_PosX * cChunkDef::Width + a_RelX;
+	int BlockZ = m_PosZ * cChunkDef::Width + a_RelZ;
+	struct
 	{
-		return;
+		int x, y, z;
 	}
-	
-	m_ToTickBlocks.push_back(MakeIndexNoCheck(a_RelX, a_RelY, a_RelZ));
+	Coords[] =
+	{
+		{ 1,  0,  0},
+		{-1,  0,  0},
+		{ 0,  1,  0},
+		{ 0, -1,  0},
+		{ 0,  0,  1},
+		{ 0,  0, -1},
+	} ;
+	for (int i = 0; i < ARRAYCOUNT(Coords); i++)
+	{
+		cChunk * ch = GetNeighborChunk(BlockX + Coords[i].x, a_RelY, BlockZ + Coords[i].z);
+		if (ch != NULL)
+		{
+			ch->QueueTickBlock(a_RelX + Coords[i].x, a_RelY + Coords[i].y, a_RelZ + Coords[i].z);
+		}
+	}  // for i - Coords[]
 }
 
 
 
 
 
-void cChunk::FastSetBlock( int a_X, int a_Y, int a_Z, BLOCKTYPE a_BlockType, BLOCKTYPE a_BlockMeta)
+void cChunk::FastSetBlock(int a_X, int a_Y, int a_Z, BLOCKTYPE a_BlockType, BLOCKTYPE a_BlockMeta)
 {
 	ASSERT(!((a_X < 0 || a_X >= Width || a_Y < 0 || a_Y >= Height || a_Z < 0 || a_Z >= Width)));
 
@@ -1833,6 +1805,74 @@ void cChunk::GetBlockInfo(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_Bloc
 
 
 
+cChunk * cChunk::GetNeighborChunk(int a_BlockX, int a_BlockY, int a_BlockZ)
+{
+	// Convert coords to relative, then call the relative version:
+	a_BlockX -= m_PosX * cChunkDef::Width;
+	a_BlockZ -= m_PosZ * cChunkDef::Width;
+	return GetRelNeighborChunk(a_BlockX, a_BlockY, a_BlockZ);
+}
+
+
+
+
+
+cChunk * cChunk::GetRelNeighborChunk(int a_RelX, int a_RelY, int a_RelZ)
+{
+	bool ReturnThis = true;
+	if (a_RelX < 0)
+	{
+		if (m_NeighborXM != NULL)
+		{
+			cChunk * Candidate = m_NeighborXM->GetRelNeighborChunk(a_RelX + cChunkDef::Width, a_RelY, a_RelZ);
+			if (Candidate != NULL)
+			{
+				return Candidate;
+			}
+		}
+		// Going X first failed, but if the request is crossing Z as well, let's try the Z first later on.
+		ReturnThis = false;
+	}
+	else if (a_RelX >= cChunkDef::Width)
+	{
+		if (m_NeighborXP != NULL)
+		{
+			cChunk * Candidate = m_NeighborXP->GetRelNeighborChunk(a_RelX - cChunkDef::Width, a_RelY, a_RelZ);
+			if (Candidate != NULL)
+			{
+				return Candidate;
+			}
+		}
+		// Going X first failed, but if the request is crossing Z as well, let's try the Z first later on.
+		ReturnThis = false;
+	}
+	
+	if (a_RelZ < 0)
+	{
+		if (m_NeighborZM != NULL)
+		{
+			return m_NeighborZM->GetRelNeighborChunk(a_RelX, a_RelY, a_RelZ + cChunkDef::Width);
+			// For requests crossing both X and Z, the X-first way has been already tried
+		}
+		return NULL;
+	}																																																 
+	else if (a_RelZ >= cChunkDef::Width)																																	 
+	{																																																 
+		if (m_NeighborZP != NULL)
+		{
+			return m_NeighborZP->GetRelNeighborChunk(a_RelX, a_RelY, a_RelZ - cChunkDef::Width);
+			// For requests crossing both X and Z, the X-first way has been already tried
+		}
+		return NULL;
+	}
+	
+	return (ReturnThis ? this : NULL);
+}
+
+
+
+
+
 void cChunk::BroadcastPlayerAnimation(const cPlayer & a_Player, char a_Animation, const cClientHandle * a_Exclude)
 {
 	for (cClientHandleList::const_iterator itr = m_LoadedByClient.begin(); itr != m_LoadedByClient.end(); ++itr )
diff --git a/source/Chunk.h b/source/Chunk.h
index 7985bbff0..324929cac 100644
--- a/source/Chunk.h
+++ b/source/Chunk.h
@@ -131,16 +131,30 @@ public:
 	void SetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta );
 	// SetBlock() does a lot of work (heightmap, tickblocks, blockentities) so a BlockIdx version doesn't make sense
 	void SetBlock( const Vector3i & a_RelBlockPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta ) { SetBlock( a_RelBlockPos.x, a_RelBlockPos.y, a_RelBlockPos.z, a_BlockType, a_BlockMeta ); }
-	void CheckBlock(int a_RelX, int a_RelY, int a_RelZ);
+	
+	/// Queues block for ticking (m_ToTickQueue)
+	void QueueTickBlock(int a_RelX, int a_RelY, int a_RelZ);
+	
+	/// Queues all 6 neighbors of the specified block for ticking (m_ToTickQueue). If any are outside the chunk, relays the checking to the proper neighboring chunk
+	void QueueTickBlockNeighbors(int a_RelX, int a_RelY, int a_RelZ);
+
 	void FastSetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, BLOCKTYPE a_BlockMeta );  // Doesn't force block updates on neighbors, use for simple changes such as grass growing etc.
 	BLOCKTYPE GetBlock( int a_X, int a_Y, int a_Z );
 	BLOCKTYPE GetBlock( int a_BlockIdx );
 	void      GetBlockTypeMeta(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta);
 	void      GetBlockInfo    (int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_Meta, NIBBLETYPE & a_SkyLight, NIBBLETYPE & a_BlockLight);
 	
-	/// Queues all 6 neighbors of the specified block for checking. If outside the chunk, relays the checking to the neighboring chunk
-	void CheckNeighbors(int a_RelX, int a_RelY, int a_RelZ);
-
+	/** Returns the chunk into which the specified block belongs, by walking the neighbors.
+	Will return self if appropriate. Returns NULL if not reachable through neighbors.
+	*/
+	cChunk * GetNeighborChunk(int a_BlockX, int a_BlockY, int a_BlockZ);
+	
+	/**
+	Returns the chunk into which the relatively-specified block belongs, by walking the neighbors.
+	Will return self if appropriate. Returns NULL if not reachable through neighbors.
+	*/
+	cChunk * GetRelNeighborChunk(int a_RelX, int a_RelY, int a_RelZ);
+	
 	EMCSBiome GetBiomeAt(int a_RelX, int a_RelZ) const {return cChunkDef::GetBiome(m_BiomeMap, a_RelX, a_RelZ); }
 	
 	void CollectPickupsByPlayer(cPlayer * a_Player);
diff --git a/source/ChunkMap.cpp b/source/ChunkMap.cpp
index 5ccdf35ca..824c7cbfe 100644
--- a/source/ChunkMap.cpp
+++ b/source/ChunkMap.cpp
@@ -641,6 +641,23 @@ void cChunkMap::UseBlockEntity(cPlayer * a_Player, int a_BlockX, int a_BlockY, i
 
 
 
+void cChunkMap::WakeUpSimulators(int a_BlockX, int a_BlockY, int a_BlockZ)
+{
+	cCSLock Lock(m_CSLayers);
+	int ChunkX, ChunkZ;
+	cChunkDef::BlockToChunk(a_BlockX, a_BlockY, a_BlockZ, ChunkX, ChunkZ);
+	cChunkPtr Chunk = GetChunkNoGen(ChunkX, 0, ChunkZ);
+	if ((Chunk == NULL) || !Chunk->IsValid())
+	{
+		return;
+	}
+	m_World->GetSimulatorManager()->WakeUp(a_BlockX, a_BlockY, a_BlockZ, Chunk);
+}
+
+
+
+
+
 void cChunkMap::MarkChunkDirty (int a_ChunkX, int a_ChunkY, int a_ChunkZ)
 {
 	cCSLock Lock(m_CSLayers);
@@ -1002,6 +1019,7 @@ void cChunkMap::SetBlock(int a_BlockX, int a_BlockY, int a_BlockZ, BLOCKTYPE a_B
 	if ((Chunk != NULL) && Chunk->IsValid())
 	{
 		Chunk->SetBlock(X, Y, Z, a_BlockType, a_BlockMeta );
+		m_World->GetSimulatorManager()->WakeUp(a_BlockX, a_BlockY, a_BlockZ, Chunk);
 	}
 }
 
@@ -1164,10 +1182,9 @@ bool cChunkMap::DigBlock(int a_X, int a_Y, int a_Z)
 		}
 		
 		DestChunk->SetBlock(PosX, PosY, PosZ, E_BLOCK_AIR, 0 );
+		m_World->GetSimulatorManager()->WakeUp(a_X, a_Y, a_Z, DestChunk);
 	}
 
-	m_World->GetSimulatorManager()->WakeUp(a_X, a_Y, a_Z);
-
 	return true;
 }
 
@@ -1810,7 +1827,7 @@ void cChunkMap::ChunkValidated(void)
 
 
 
-void cChunkMap::CheckBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cChunkMap::QueueTickBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
 {
 	int ChunkX, ChunkZ;
 	cChunkDef::AbsoluteToRelative(a_BlockX, a_BlockY, a_BlockZ, ChunkX, ChunkZ);
@@ -1820,7 +1837,7 @@ void cChunkMap::CheckBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
 	cChunkPtr Chunk = GetChunkNoLoad(ChunkX, ZERO_CHUNK_Y, ChunkZ);
 	if (Chunk != NULL)
 	{
-		Chunk->CheckBlock(a_BlockX, a_BlockY, a_BlockZ);
+		Chunk->QueueTickBlock(a_BlockX, a_BlockY, a_BlockZ);
 	}
 }
 
diff --git a/source/ChunkMap.h b/source/ChunkMap.h
index 12c6e7275..86cbf35a2 100644
--- a/source/ChunkMap.h
+++ b/source/ChunkMap.h
@@ -96,6 +96,9 @@ public:
 	
 	/// a_Player rclked block entity at the coords specified, handle it
 	void UseBlockEntity(cPlayer * a_Player, int a_X, int a_Y, int a_Z);
+	
+	/// Wakes up simulators for the specified block
+	void WakeUpSimulators(int a_BlockX, int a_BlockY, int a_BlockZ);
 
 	void MarkChunkDirty     (int a_ChunkX, int a_ChunkY, int a_ChunkZ);
 	void MarkChunkSaving    (int a_ChunkX, int a_ChunkY, int a_ChunkZ);
@@ -256,8 +259,8 @@ public:
 	
 	void ChunkValidated(void);  // Called by chunks that have become valid
 	
-	/// Schedules the specified block for checking (block update)
-	void CheckBlock(int a_BlockX, int a_BlockY, int a_BlockZ);
+	/// Queues the specified block for ticking (block update)
+	void QueueTickBlock(int a_BlockX, int a_BlockY, int a_BlockZ);
 
 private:
 
diff --git a/source/Simulator/ClassicFluidSimulator.cpp b/source/Simulator/ClassicFluidSimulator.cpp
index e195ffdc5..e005e7381 100644
--- a/source/Simulator/ClassicFluidSimulator.cpp
+++ b/source/Simulator/ClassicFluidSimulator.cpp
@@ -284,8 +284,9 @@ cClassicFluidSimulator::~cClassicFluidSimulator()
 
 
 
-void cClassicFluidSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cClassicFluidSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
+	// TODO: This can be optimized
 	BLOCKTYPE BlockType = m_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ);
 	if (!IsAllowedBlock(BlockType))		// This should save very much time because it doesn�t have to iterate through all blocks
 	{
@@ -389,17 +390,15 @@ void cClassicFluidSimulator::Simulate(float a_Dt)
 					}
 					if (pos.y > 0)
 					{
-						m_World->FastSetBlock( pos.x, pos.y-1, pos.z, m_FluidBlock, 8 ); // falling
-						AddBlock( pos.x, pos.y-1, pos.z );
+						m_World->SetBlock(pos.x, pos.y - 1, pos.z, m_FluidBlock, 8); // falling
 						ApplyUniqueToNearest(pos - Vector3i(0, 1, 0));
 					}
 				}
-				if (IsSolidBlock(DownID)||( BlockID == m_StationaryFluidBlock)) // Not falling
+				if (IsSolidBlock(DownID) || (BlockID == m_StationaryFluidBlock)) // Not falling
 				{
 					if (Feed + m_Falloff < Meta)
 					{
-						m_World->FastSetBlock( pos.x, pos.y, pos.z, m_FluidBlock, Feed + m_Falloff);
-						AddBlock( pos.x, pos.y, pos.z );
+						m_World->SetBlock(pos.x, pos.y, pos.z, m_FluidBlock, Feed + m_Falloff);
 						ApplyUniqueToNearest(pos);
 					}
 					else if ((Meta < m_MaxHeight ) || (BlockID == m_StationaryFluidBlock)) // max is the lowest, so it cannot spread					
@@ -426,21 +425,20 @@ void cClassicFluidSimulator::Simulate(float a_Dt)
 
 								if (p.y == pos.y)
 								{
-									m_World->FastSetBlock(p.x, p.y, p.z, m_FluidBlock, Meta + m_Falloff);
+									m_World->SetBlock(p.x, p.y, p.z, m_FluidBlock, Meta + m_Falloff);
 								}
 								else
 								{
-									m_World->FastSetBlock(p.x, p.y, p.z, m_FluidBlock, 8);
+									m_World->SetBlock(p.x, p.y, p.z, m_FluidBlock, 8);
 								}
-								AddBlock( p.x, p.y, p.z );
 								ApplyUniqueToNearest(p);
 							}
 							else // it's fluid
 							{
-								char PointMeta = m_World->GetBlockMeta( p.x, p.y, p.z );
-								if( PointMeta > Meta + m_Falloff)
+								NIBBLETYPE PointMeta = m_World->GetBlockMeta(p.x, p.y, p.z);
+								if (PointMeta > Meta + m_Falloff)
 								{
-									AddBlock( p.x, p.y, p.z );
+									// TODO: AddBlock(p.x, p.y, p.z);
 									ApplyUniqueToNearest(p);
 								}
 							}
@@ -448,10 +446,9 @@ void cClassicFluidSimulator::Simulate(float a_Dt)
 					}
 				}
 			}
-			else// not fed
+			else  // not fed
 			{
-				m_World->FastSetBlock( pos.x, pos.y, pos.z, E_BLOCK_AIR, 0 );
-				WakeUp( pos.x, pos.y, pos.z );
+				m_World->SetBlock(pos.x, pos.y, pos.z, E_BLOCK_AIR, 0);
 			}
 		}
 	}
diff --git a/source/Simulator/ClassicFluidSimulator.h b/source/Simulator/ClassicFluidSimulator.h
index 4198f16de..95dfd9e4a 100644
--- a/source/Simulator/ClassicFluidSimulator.h
+++ b/source/Simulator/ClassicFluidSimulator.h
@@ -24,7 +24,7 @@ public:
 
 	// cSimulator overrides:
 	virtual void Simulate(float a_Dt) override;
-	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ) override;
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override;
 
 protected:
 	NIBBLETYPE GetHighestLevelAround(int a_BlockX, int a_BlockY, int a_BlockZ);
diff --git a/source/Simulator/DelayedFluidSimulator.cpp b/source/Simulator/DelayedFluidSimulator.cpp
index 317452c57..e0faf5b18 100644
--- a/source/Simulator/DelayedFluidSimulator.cpp
+++ b/source/Simulator/DelayedFluidSimulator.cpp
@@ -36,7 +36,7 @@ cDelayedFluidSimulator::~cDelayedFluidSimulator()
 
 
 
-void cDelayedFluidSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cDelayedFluidSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
 	if ((a_BlockY < 0) || (a_BlockY >= cChunkDef::Height))
 	{
@@ -44,6 +44,7 @@ void cDelayedFluidSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
 		return;
 	}
 	
+	// TODO: This can be optimized:
 	BLOCKTYPE BlockType = m_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ);
 	if (BlockType != m_FluidBlock)
 	{
diff --git a/source/Simulator/DelayedFluidSimulator.h b/source/Simulator/DelayedFluidSimulator.h
index 51fe2a514..d8ba3f858 100644
--- a/source/Simulator/DelayedFluidSimulator.h
+++ b/source/Simulator/DelayedFluidSimulator.h
@@ -25,7 +25,7 @@ public:
 	virtual ~cDelayedFluidSimulator();
 	
 	// cSimulator overrides:
-	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ) override;
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override;
 	virtual void Simulate(float a_Dt) override;
 	
 protected:
diff --git a/source/Simulator/FireSimulator.cpp b/source/Simulator/FireSimulator.cpp
index 8579c2c17..0ebac74b3 100644
--- a/source/Simulator/FireSimulator.cpp
+++ b/source/Simulator/FireSimulator.cpp
@@ -72,8 +72,9 @@ bool cFireSimulator::IsAllowedBlock(BLOCKTYPE a_BlockType)
 
 
 
-void cFireSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cFireSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
+	// TODO: This can be optimized
 	BLOCKTYPE BlockType = m_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ);
 	if (!IsAllowedBlock(BlockType))
 	{
diff --git a/source/Simulator/FireSimulator.h b/source/Simulator/FireSimulator.h
index 826d24340..d95ecf4f0 100644
--- a/source/Simulator/FireSimulator.h
+++ b/source/Simulator/FireSimulator.h
@@ -23,7 +23,7 @@ public:
 	virtual bool FiresForever( BLOCKTYPE a_BlockType );
 
 protected:
-	virtual void AddBlock(int a_X, int a_Y, int a_Z) override;
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override;
 	virtual bool BurnBlockAround(int a_X, int a_Y, int a_Z);
 	virtual bool BurnBlock(int a_X, int a_Y, int a_Z);
 
diff --git a/source/Simulator/RedstoneSimulator.cpp b/source/Simulator/RedstoneSimulator.cpp
index 1862537e0..d6afda413 100644
--- a/source/Simulator/RedstoneSimulator.cpp
+++ b/source/Simulator/RedstoneSimulator.cpp
@@ -29,10 +29,9 @@ cRedstoneSimulator::~cRedstoneSimulator()
 
 
 
-void cRedstoneSimulator::WakeUp( int a_X, int a_Y, int a_Z )
+void cRedstoneSimulator::WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
-	cCSLock Lock( m_CS );
-	m_Blocks.push_back( Vector3i( a_X, a_Y, a_Z ) );
+	m_Blocks.push_back(Vector3i(a_BlockX, a_BlockY, a_BlockZ));
 }
 
 
diff --git a/source/Simulator/RedstoneSimulator.h b/source/Simulator/RedstoneSimulator.h
index 0b0333164..df5874d07 100644
--- a/source/Simulator/RedstoneSimulator.h
+++ b/source/Simulator/RedstoneSimulator.h
@@ -18,7 +18,7 @@ public:
 	virtual void Simulate( float a_Dt ) override;
 	virtual bool IsAllowedBlock( BLOCKTYPE a_BlockType ) override { return true; }
 
-	virtual void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ) override;
+	virtual void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override;
 
 	enum eRedstoneDirection
 	{
@@ -56,7 +56,7 @@ private:
 	
 	void SetRepeater(const Vector3i & a_Position, int a_Ticks, bool a_bPowerOn);
 
-	virtual void AddBlock(int a_X, int a_Y, int a_Z) {}
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override {}
 
 	void HandleChange( const Vector3i & a_BlockPos );
 	BlockList RemoveCurrent( const Vector3i & a_BlockPos );
@@ -77,6 +77,7 @@ private:
 	
 	void RefreshTorchesAround( const Vector3i & a_BlockPos );
 
+	// TODO: The entire simulator is synchronized, no need to lock data structures; remove this
 	cCriticalSection m_CS;
 };
 
diff --git a/source/Simulator/SandSimulator.cpp b/source/Simulator/SandSimulator.cpp
index 69513afef..f9d58f030 100644
--- a/source/Simulator/SandSimulator.cpp
+++ b/source/Simulator/SandSimulator.cpp
@@ -6,6 +6,8 @@
 #include "../BlockID.h"
 #include "../Defines.h"
 #include "../FallingBlock.h"
+#include "../Chunk.h"
+
 
 
 
@@ -70,19 +72,29 @@ bool cSandSimulator::IsAllowedBlock( BLOCKTYPE a_BlockType )
 
 
 
-void cSandSimulator::AddBlock(int a_X, int a_Y, int a_Z)
+void cSandSimulator::AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
-	if(!IsAllowedBlock(m_World->GetBlock(a_X, a_Y, a_Z)))
+	// TODO: Optimize this by passing the block type along
+	int RelX = a_BlockX;
+	int RelY = a_BlockY;
+	int RelZ = a_BlockZ;
+	int ChunkX, ChunkZ;
+	cChunkDef::AbsoluteToRelative(RelX, RelY, RelZ, ChunkX, ChunkZ);
+	if (!IsAllowedBlock(a_Chunk->GetBlock(RelX, RelY, RelZ)))
+	{
 		return;
+	}
 
-	Vector3i Block(a_X, a_Y, a_Z);
+	Vector3i Block(a_BlockX, a_BlockY, a_BlockZ);
 	
 	//check for duplicates
-	for( BlockList::iterator itr = m_Blocks->begin(); itr != m_Blocks->end(); ++itr )
+	for (BlockList::iterator itr = m_Blocks->begin(); itr != m_Blocks->end(); ++itr)
 	{
 		Vector3i Pos = *itr;
-		if( Pos.x == a_X && Pos.y == a_Y && Pos.z == a_Z )
+		if ((Pos.x == a_BlockX) && (Pos.y == a_BlockY) && (Pos.z == a_BlockZ))
+		{
 			return;
+		}
 	}
 
 	m_Blocks->push_back(Block);
@@ -92,10 +104,10 @@ void cSandSimulator::AddBlock(int a_X, int a_Y, int a_Z)
 
 
 
-bool cSandSimulator::IsPassable( BLOCKTYPE a_BlockType )
+bool cSandSimulator::IsPassable(BLOCKTYPE a_BlockType)
 {
-	return a_BlockType == E_BLOCK_AIR
+	return (a_BlockType == E_BLOCK_AIR)
 		|| IsBlockWater(a_BlockType)
 		|| IsBlockLava(a_BlockType)
-		|| a_BlockType == E_BLOCK_FIRE;
+		|| (a_BlockType == E_BLOCK_FIRE);
 }
diff --git a/source/Simulator/SandSimulator.h b/source/Simulator/SandSimulator.h
index 928ea63fc..4b786678c 100644
--- a/source/Simulator/SandSimulator.h
+++ b/source/Simulator/SandSimulator.h
@@ -21,7 +21,7 @@ public:
 	virtual bool IsPassable( BLOCKTYPE a_BlockType );
 
 protected:
-	virtual void AddBlock(int a_X, int a_Y, int a_Z) override;
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) override;
 
 	typedef std::list <Vector3i> BlockList;
 	BlockList * m_Blocks;
diff --git a/source/Simulator/Simulator.cpp b/source/Simulator/Simulator.cpp
index 86b37e989..8560163c5 100644
--- a/source/Simulator/Simulator.cpp
+++ b/source/Simulator/Simulator.cpp
@@ -6,6 +6,7 @@
 #include "../Vector3i.h"
 #include "../BlockID.h"
 #include "../Defines.h"
+#include "../Chunk.h"
 
 
 
@@ -28,15 +29,15 @@ cSimulator::~cSimulator()
 
 
 
-void cSimulator::WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cSimulator::WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
-	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ);
-	AddBlock(a_BlockX - 1, a_BlockY,     a_BlockZ);
-	AddBlock(a_BlockX + 1, a_BlockY,     a_BlockZ);
-	AddBlock(a_BlockX,     a_BlockY - 1, a_BlockZ);
-	AddBlock(a_BlockX,     a_BlockY + 1, a_BlockZ);
-	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ - 1);
-	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ + 1);
+	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ,     a_Chunk);
+	AddBlock(a_BlockX,     a_BlockY - 1, a_BlockZ,     a_Chunk);
+	AddBlock(a_BlockX,     a_BlockY + 1, a_BlockZ,     a_Chunk);
+	AddBlock(a_BlockX - 1, a_BlockY,     a_BlockZ,     a_Chunk->GetNeighborChunk(a_BlockX - 1, a_BlockY, a_BlockZ));
+	AddBlock(a_BlockX + 1, a_BlockY,     a_BlockZ,     a_Chunk->GetNeighborChunk(a_BlockX + 1, a_BlockY, a_BlockZ));
+	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ - 1, a_Chunk->GetNeighborChunk(a_BlockX,     a_BlockY, a_BlockZ - 1));
+	AddBlock(a_BlockX,     a_BlockY,     a_BlockZ + 1, a_Chunk->GetNeighborChunk(a_BlockX,     a_BlockY, a_BlockZ + 1));
 }
 
 
diff --git a/source/Simulator/Simulator.h b/source/Simulator/Simulator.h
index 1fecb0c96..ee3489b02 100644
--- a/source/Simulator/Simulator.h
+++ b/source/Simulator/Simulator.h
@@ -8,6 +8,7 @@
 
 
 class cWorld;
+class cChunk;
 
 
 
@@ -19,17 +20,17 @@ public:
 	cSimulator(cWorld * a_World);
 	virtual ~cSimulator();
 
-	/// Called in each tick, a_Dt is the time passed since the last tick
+	/// Called in each tick, a_Dt is the time passed since the last tick, in msec
 	virtual void Simulate(float a_Dt) = 0;
 	
-	/// Called when a block changes via cWorld::SetBlock()
-	virtual void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ);
+	/// Called when a block changes
+	virtual void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk);
 
 	virtual bool IsAllowedBlock(BLOCKTYPE a_BlockType) = 0;
 
 protected:
 	/// Called to simulate a new block
-	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ) = 0;
+	virtual void AddBlock(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk) = 0;
 
 	cWorld * m_World;
 } ;
diff --git a/source/Simulator/SimulatorManager.cpp b/source/Simulator/SimulatorManager.cpp
index c74b273f7..ceebc2d8f 100644
--- a/source/Simulator/SimulatorManager.cpp
+++ b/source/Simulator/SimulatorManager.cpp
@@ -40,11 +40,11 @@ void cSimulatorManager::Simulate( float a_Dt )
 
 
 
-void cSimulatorManager::WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ)
+void cSimulatorManager::WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk)
 {
 	for (cSimulators::iterator itr = m_Simulators.begin(); itr != m_Simulators.end(); ++itr )
 	{
-		itr->first->WakeUp(a_BlockX, a_BlockY, a_BlockZ);
+		itr->first->WakeUp(a_BlockX, a_BlockY, a_BlockZ, a_Chunk);
 	}
 }
 
diff --git a/source/Simulator/SimulatorManager.h b/source/Simulator/SimulatorManager.h
index fbd97b8fa..989831b03 100644
--- a/source/Simulator/SimulatorManager.h
+++ b/source/Simulator/SimulatorManager.h
@@ -15,6 +15,13 @@
 
 
 
+// fwd: Chunk.h
+class cChunk;
+
+
+
+
+
 class cSimulatorManager
 {
 public:
@@ -22,7 +29,7 @@ public:
 	~cSimulatorManager();
 
 	void Simulate(float a_Dt);
-	void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ);
+	void WakeUp(int a_BlockX, int a_BlockY, int a_BlockZ, cChunk * a_Chunk);
 
 	void RegisterSimulator(cSimulator * a_Simulator, int a_Rate);  // Takes ownership of the simulator object!
 
diff --git a/source/World.cpp b/source/World.cpp
index 2c31371d2..0236a456b 100644
--- a/source/World.cpp
+++ b/source/World.cpp
@@ -687,6 +687,15 @@ void cWorld::TickSpawnMobs(float a_Dt)
 
 
 
+void cWorld::WakeUpSimulators(int a_BlockX, int a_BlockY, int a_BlockZ)
+{
+	return m_ChunkMap->WakeUpSimulators(a_BlockX, a_BlockY, a_BlockZ);
+}
+
+
+
+
+
 bool cWorld::ForEachChestInChunk(int a_ChunkX, int a_ChunkZ, cChestCallback & a_Callback)
 {
 	return m_ChunkMap->ForEachChestInChunk(a_ChunkX, a_ChunkZ, a_Callback);
@@ -1030,7 +1039,6 @@ void cWorld::SetBlock(int a_BlockX, int a_BlockY, int a_BlockZ, BLOCKTYPE a_Bloc
 	}
 	m_ChunkMap->SetBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockType, a_BlockMeta);
 
-	GetSimulatorManager()->WakeUp(a_BlockX, a_BlockY, a_BlockZ);
 	BlockHandler(a_BlockType)->OnPlaced(this, a_BlockX, a_BlockY, a_BlockZ, a_BlockType, a_BlockMeta);
 }
 
diff --git a/source/World.h b/source/World.h
index b744a66c1..6fc3fa088 100644
--- a/source/World.h
+++ b/source/World.h
@@ -312,6 +312,9 @@ public:
 	
 	inline cFluidSimulator * GetWaterSimulator(void) { return m_WaterSimulator; }
 	inline cFluidSimulator * GetLavaSimulator (void) { return m_LavaSimulator; }
+	
+	/// Wakes up the simulators for the specified block
+	void WakeUpSimulators(int a_BlockX, int a_BlockY, int a_BlockZ);
 
 	/// Calls the callback for each chest in the specified chunk; returns true if all chests processed, false if the callback aborted by returning true
 	bool ForEachChestInChunk  (int a_ChunkX, int a_ChunkZ, cChestCallback &   a_Callback);  // Exported in ManualBindings.cpp