1 files changed, 8 insertions, 2 deletions

diff --git a/src/Simulator/VanillaFluidSimulator.cpp b/src/Simulator/VanillaFluidSimulator.cpp
index 78aff9d68..18d9b07e1 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;
 	}