4 files changed, 20 insertions, 14 deletions
diff --git a/src/Simulator/FloodyFluidSimulator.cpp b/src/Simulator/FloodyFluidSimulator.cpp
index 03e94e791..e95af3a1c 100644
--- a/src/Simulator/FloodyFluidSimulator.cpp
+++ b/src/Simulator/FloodyFluidSimulator.cpp
@@ -119,7 +119,7 @@ void cFloodyFluidSimulator::SimulateBlock(cChunk * a_Chunk, int a_RelX, int a_Re
 	if (SpreadFurther && (NewMeta < 8))
 	{
 		// Spread to the neighbors:
-		Spread(a_Chunk, a_RelX, a_RelY, a_RelZ, NewMeta);
+		SpreadXZ(a_Chunk, a_RelX, a_RelY, a_RelZ, NewMeta);
 	}
 	
 	// Mark as processed:
@@ -130,7 +130,7 @@ void cFloodyFluidSimulator::SimulateBlock(cChunk * a_Chunk, int a_RelX, int a_Re
 
 
 
-void cFloodyFluidSimulator::Spread(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta)
+void cFloodyFluidSimulator::SpreadXZ(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta)
 {
 	SpreadToNeighbor(a_Chunk, a_RelX - 1, a_RelY, a_RelZ,     a_NewMeta);
 	SpreadToNeighbor(a_Chunk, a_RelX + 1, a_RelY, a_RelZ,     a_NewMeta);
diff --git a/src/Simulator/FloodyFluidSimulator.h b/src/Simulator/FloodyFluidSimulator.h
index 632de3bb2..8e1be5e6b 100644
--- a/src/Simulator/FloodyFluidSimulator.h
+++ b/src/Simulator/FloodyFluidSimulator.h
@@ -48,16 +48,13 @@ protected:
 	bool CheckNeighborsForSource(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ);
 
 	/** Checks if the specified block should harden (Water/Lava interaction) and if so, converts it to a suitable block.
-	 *
-	 * Returns whether the block was changed or not.
-	 */
+	Returns whether the block was changed or not. */
 	bool HardenBlock(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_Meta);
 
-	/** Spread water to neighbors.
-	 *
-	 * May be overridden to provide more sophisticated algorithms.
-	 */
-	virtual void Spread(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta);
+	/** Spread fluid to XZ neighbors.
+	The coords are of the block currently being processed; a_NewMeta is the new meta for the new fluid block.
+	Descendants may overridde to provide more sophisticated algorithms. */
+	virtual void SpreadXZ(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta);
 } ;
 
 
diff --git a/src/Simulator/VanillaFluidSimulator.cpp b/src/Simulator/VanillaFluidSimulator.cpp
index 78aff9d68..28d75214c 100644
--- a/src/Simulator/VanillaFluidSimulator.cpp
+++ b/src/Simulator/VanillaFluidSimulator.cpp
@@ -35,14 +35,16 @@ cVanillaFluidSimulator::cVanillaFluidSimulator(
 
 
 
-void cVanillaFluidSimulator::Spread(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta)
+void cVanillaFluidSimulator::SpreadXZ(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta)
 {
+	// Calculate the distance to the nearest "hole" in each direction:
 	int Cost[4];
 	Cost[0] = CalculateFlowCost(a_Chunk, a_RelX + 1, a_RelY, a_RelZ,     X_PLUS);
 	Cost[1] = CalculateFlowCost(a_Chunk, a_RelX - 1, a_RelY, a_RelZ,     X_MINUS);
 	Cost[2] = CalculateFlowCost(a_Chunk, a_RelX,     a_RelY, a_RelZ + 1, Z_PLUS);
 	Cost[3] = CalculateFlowCost(a_Chunk, a_RelX,     a_RelY, a_RelZ - 1, Z_MINUS);
 
+	// Find the minimum distance:
 	int MinCost = InfiniteCost;
 	for (unsigned int i = 0; i < ARRAYCOUNT(Cost); ++i)
 	{
@@ -52,6 +54,7 @@ void cVanillaFluidSimulator::Spread(cChunk * a_Chunk, int a_RelX, int a_RelY, in
 		}
 	}
 
+	// Spread in all directions where the distance matches the minimum:
 	if (Cost[0] == MinCost)
 	{
 		SpreadToNeighbor(a_Chunk, a_RelX + 1, a_RelY, a_RelZ, a_NewMeta);
@@ -86,7 +89,10 @@ int cVanillaFluidSimulator::CalculateFlowCost(cChunk * a_Chunk, int a_RelX, int
 	{
 		return Cost;
 	}
-	if (!IsPassableForFluid(BlockType) && !IsBlockLiquid(BlockType))
+	if (
+		!IsPassableForFluid(BlockType) ||                 // The block cannot be passed by the liquid ...
+		(IsAllowedBlock(BlockType) && (BlockMeta == 0))  // ... or if it is liquid, it is a source block
+	)
 	{
 		return Cost;
 	}
@@ -96,7 +102,10 @@ int cVanillaFluidSimulator::CalculateFlowCost(cChunk * a_Chunk, int a_RelX, int
 	{
 		return Cost;
 	}
-	if (IsPassableForFluid(BlockType) || IsBlockLiquid(BlockType))
+	if (
+		IsPassableForFluid(BlockType) ||                // The block can be passed by the liquid ...
+		(IsBlockLiquid(BlockType) && (BlockMeta != 0))  // ... or it is a liquid and not a source block
+	)
 	{
 		// Path found, exit
 		return a_Iteration;
diff --git a/src/Simulator/VanillaFluidSimulator.h b/src/Simulator/VanillaFluidSimulator.h
index a9ea98b5a..89a56ca14 100644
--- a/src/Simulator/VanillaFluidSimulator.h
+++ b/src/Simulator/VanillaFluidSimulator.h
@@ -30,7 +30,7 @@ public:
 	
 protected:
 	// cFloodyFluidSimulator overrides:
-	virtual void Spread(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta) override;
+	virtual void SpreadXZ(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_NewMeta) override;
 
 	/** Recursively calculates the minimum number of blocks needed to descend a level. */
 	int CalculateFlowCost(cChunk * a_Chunk, int a_RelX, int a_RelY, int a_RelZ, Direction a_Dir, unsigned a_Iteration = 0);