3 files changed, 52 insertions, 1 deletions

diff --git a/MCServer/Plugins/APIDump/APIDesc.lua b/MCServer/Plugins/APIDump/APIDesc.lua
index 9bcd6edde..451b7364a 100644
--- a/MCServer/Plugins/APIDump/APIDesc.lua
+++ b/MCServer/Plugins/APIDump/APIDesc.lua
@@ -249,6 +249,9 @@ g_APIDesc =
 						<tr>
 						<td> A </td><td> B </td><td> B </td><td> A </td><td> B </td>
 						</tr>
+						<tr>
+						<td> A </td><td> A </td><td> A </td><td> A </td><td> A </td>
+						</td>
 						</tbody></table>
 
 						<p>
@@ -262,7 +265,20 @@ g_APIDesc =
 
 						<h3>Special strategies</h3>
 						<p>For each strategy, evaluate the table rows from top downwards, the first match wins.</p>
-
+						
+						<p>
+						<strong>msDifference</strong> - changes all the blocks which are the same to air. Otherwise the source block gets placed.
+						</p>
+						<table><tbody<tr>
+						<th colspan="2"> area block </th><th> </th><th> Notes </th>
+						</tr><tr>
+						<td> * </td><td> B </td><td> B </td><td> The blocks are different so we use block B </td>
+						</tr><tr>
+						<td> B </td><td> B </td><td> Air </td><td> The blocks are the same so we get air. </td>
+						</tr>
+						</tbody></table>
+						
+						
 						<p>
 						<strong>msLake</strong> - used for merging areas with lava and water lakes, in the appropriate generator.
 						</p>
diff --git a/src/BlockArea.cpp b/src/BlockArea.cpp
index 543dbe04d..60e4f11e5 100644
--- a/src/BlockArea.cpp
+++ b/src/BlockArea.cpp
@@ -173,6 +173,25 @@ static inline void MergeCombinatorSpongePrint(BLOCKTYPE & a_DstType, BLOCKTYPE a
 
 
 
+/** Combinator used for cBlockArea::msDifference merging */
+static inline void MergeCombinatorDifference(BLOCKTYPE & a_DstType, BLOCKTYPE a_SrcType, NIBBLETYPE & a_DstMeta, NIBBLETYPE a_SrcMeta)
+{
+	if ((a_DstType == a_SrcType) && (a_DstMeta == a_SrcMeta))
+	{
+		a_DstType = E_BLOCK_AIR;
+		a_DstMeta = 0;
+	}
+	else
+	{
+		a_DstType = a_SrcType;
+		a_DstMeta = a_SrcMeta;
+	}
+}
+
+
+
+
+
 /** Combinator used for cBlockArea::msMask merging */
 static inline void MergeCombinatorMask(BLOCKTYPE & a_DstType, BLOCKTYPE a_SrcType, NIBBLETYPE & a_DstMeta, NIBBLETYPE a_SrcMeta)
 {
@@ -724,6 +743,21 @@ void cBlockArea::Merge(const cBlockArea & a_Src, int a_RelX, int a_RelY, int a_R
 			);
 			break;
 		}  // case msSpongePrint
+
+		case msDifference:
+		{
+			InternalMergeBlocks(
+				m_BlockTypes, a_Src.GetBlockTypes(),
+				DstMetas, SrcMetas,
+				SizeX, SizeY, SizeZ,
+				SrcOffX, SrcOffY, SrcOffZ,
+				DstOffX, DstOffY, DstOffZ,
+				a_Src.GetSizeX(), a_Src.GetSizeY(), a_Src.GetSizeZ(),
+				m_Size.x, m_Size.y, m_Size.z,
+				MergeCombinatorDifference
+			);
+			break;
+		}	// case msDifference
 		
 		case msMask:
 		{
diff --git a/src/BlockArea.h b/src/BlockArea.h
index 34a0ef926..c48175b8c 100644
--- a/src/BlockArea.h
+++ b/src/BlockArea.h
@@ -52,6 +52,7 @@ public:
 		msImprint,
 		msLake,
 		msSpongePrint,
+		msDifference,
 		msMask,
 	} ;