3 files changed, 142 insertions, 54 deletions

diff --git a/src/Generating/Prefab.cpp b/src/Generating/Prefab.cpp
index 6805167a9..9af01d6a4 100644
--- a/src/Generating/Prefab.cpp
+++ b/src/Generating/Prefab.cpp
@@ -97,8 +97,8 @@ static const cPrefab::sDef g_TestPrefabDef =
 	// Merge strategy:
 	cBlockArea::msImprint,
 
-	// ShouldExtendFloor:
-	false,
+	// ExtendFloorStrategy:
+	cPrefab::efsNone,
 
 	// DefaultWeight:
 	10,
@@ -128,7 +128,7 @@ cPrefab::cPrefab(const cPrefab::sDef & a_Def) :
 	),
 	m_AllowedRotations(a_Def.m_AllowedRotations),
 	m_MergeStrategy(a_Def.m_MergeStrategy),
-	m_ShouldExtendFloor(a_Def.m_ShouldExtendFloor),
+	m_ExtendFloorStrategy(a_Def.m_ExtendFloorStrategy),
 	m_DefaultWeight(a_Def.m_DefaultWeight),
 	m_AddWeightIfSame(a_Def.m_AddWeightIfSame),
 	m_MoveToGround(a_Def.m_MoveToGround)
@@ -151,7 +151,7 @@ cPrefab::cPrefab(const cBlockArea & a_Image, int a_AllowedRotations) :
 	m_Size(a_Image.GetSize()),
 	m_AllowedRotations(a_AllowedRotations),
 	m_MergeStrategy(cBlockArea::msOverwrite),
-	m_ShouldExtendFloor(false),
+	m_ExtendFloorStrategy(efsNone),
 	m_DefaultWeight(1),
 	m_AddWeightIfSame(0),
 	m_MoveToGround(false)
@@ -170,7 +170,7 @@ cPrefab::cPrefab(const cBlockArea & a_Image) :
 	m_Size(a_Image.GetSize()),
 	m_AllowedRotations(0),
 	m_MergeStrategy(cBlockArea::msOverwrite),
-	m_ShouldExtendFloor(false),
+	m_ExtendFloorStrategy(efsNone),
 	m_DefaultWeight(1),
 	m_AddWeightIfSame(0),
 	m_MoveToGround(false)
@@ -188,7 +188,7 @@ cPrefab::cPrefab(const AString & a_BlockDefinitions, const AString & a_BlockData
 	m_Size(a_SizeX, a_SizeY, a_SizeZ),
 	m_AllowedRotations(0),
 	m_MergeStrategy(cBlockArea::msOverwrite),
-	m_ShouldExtendFloor(false),
+	m_ExtendFloorStrategy(efsNone),
 	m_DefaultWeight(1),
 	m_AddWeightIfSame(0),
 	m_MoveToGround(false)
@@ -264,46 +264,94 @@ void cPrefab::Draw(cChunkDesc & a_Dest, const Vector3i & a_Placement, int a_NumR
 	a_Dest.WriteBlockArea(Image, Placement.x, Placement.y, Placement.z, m_MergeStrategy);
 
 	// If requested, draw the floor (from the bottom of the prefab down to the nearest non-air)
-	if (m_ShouldExtendFloor)
+	switch (m_ExtendFloorStrategy)
 	{
-		int MaxX = Image.GetSizeX();
-		int MaxZ = Image.GetSizeZ();
-		for (int z = 0; z < MaxZ; z++)
+		case efsNone: break;  // Nothing needed
+		case efsRepeatBottomTillNonAir:
 		{
-			int RelZ = Placement.z + z;
-			if ((RelZ < 0) || (RelZ >= cChunkDef::Width))
-			{
-				// Z coord outside the chunk
-				continue;
-			}
-			for (int x = 0; x < MaxX; x++)
+			int MaxX = Image.GetSizeX();
+			int MaxZ = Image.GetSizeZ();
+			for (int z = 0; z < MaxZ; z++)
 			{
-				int RelX = Placement.x + x;
-				if ((RelX < 0) || (RelX >= cChunkDef::Width))
+				int RelZ = Placement.z + z;
+				if ((RelZ < 0) || (RelZ >= cChunkDef::Width))
 				{
-					// X coord outside the chunk
+					// Z coord outside the chunk
 					continue;
 				}
-				BLOCKTYPE BlockType;
-				NIBBLETYPE BlockMeta;
-				Image.GetRelBlockTypeMeta(x, 0, z, BlockType, BlockMeta);
-				if ((BlockType == E_BLOCK_AIR) || (BlockType == E_BLOCK_SPONGE))
+				for (int x = 0; x < MaxX; x++)
+				{
+					int RelX = Placement.x + x;
+					if ((RelX < 0) || (RelX >= cChunkDef::Width))
+					{
+						// X coord outside the chunk
+						continue;
+					}
+					BLOCKTYPE BlockType;
+					NIBBLETYPE BlockMeta;
+					Image.GetRelBlockTypeMeta(x, 0, z, BlockType, BlockMeta);
+					if ((BlockType == E_BLOCK_AIR) || (BlockType == E_BLOCK_SPONGE))
+					{
+						// Do not expand air nor sponge blocks
+						continue;
+					}
+					for (int y = Placement.y - 1; y >= 0; y--)
+					{
+						BLOCKTYPE ExistingBlock = a_Dest.GetBlockType(RelX, y, RelZ);
+						if (ExistingBlock != E_BLOCK_AIR)
+						{
+							// End the expansion for this column, reached the end
+							break;
+						}
+						a_Dest.SetBlockTypeMeta(RelX, y, RelZ, BlockType, BlockMeta);
+					}  // for y
+				}  // for x
+			}  // for z
+			break;
+		}  // efsRepeatBottomTillNonAir
+
+		case efsRepeatBottomTillSolid:
+		{
+			int MaxX = Image.GetSizeX();
+			int MaxZ = Image.GetSizeZ();
+			for (int z = 0; z < MaxZ; z++)
+			{
+				int RelZ = Placement.z + z;
+				if ((RelZ < 0) || (RelZ >= cChunkDef::Width))
 				{
-					// Do not expand air nor sponge blocks
+					// Z coord outside the chunk
 					continue;
 				}
-				for (int y = Placement.y - 1; y >= 0; y--)
+				for (int x = 0; x < MaxX; x++)
 				{
-					BLOCKTYPE ExistingBlock = a_Dest.GetBlockType(RelX, y, RelZ);
-					if (ExistingBlock != E_BLOCK_AIR)
+					int RelX = Placement.x + x;
+					if ((RelX < 0) || (RelX >= cChunkDef::Width))
 					{
-						// End the expansion for this column, reached the end
-						break;
+						// X coord outside the chunk
+						continue;
 					}
-					a_Dest.SetBlockTypeMeta(RelX, y, RelZ, BlockType, BlockMeta);
-				}  // for y
-			}  // for x
-		}  // for z
+					BLOCKTYPE BlockType;
+					NIBBLETYPE BlockMeta;
+					Image.GetRelBlockTypeMeta(x, 0, z, BlockType, BlockMeta);
+					if ((BlockType == E_BLOCK_AIR) || (BlockType == E_BLOCK_SPONGE))
+					{
+						// Do not expand air nor sponge blocks
+						continue;
+					}
+					for (int y = Placement.y - 1; y >= 0; y--)
+					{
+						BLOCKTYPE ExistingBlock = a_Dest.GetBlockType(RelX, y, RelZ);
+						if (cBlockInfo::IsSolid(ExistingBlock))
+						{
+							// End the expansion for this column, reached the end
+							break;
+						}
+						a_Dest.SetBlockTypeMeta(RelX, y, RelZ, BlockType, BlockMeta);
+					}  // for y
+				}  // for x
+			}  // for z
+			break;
+		}  // efsRepeatBottomTillSolid
 	}
 }
 
diff --git a/src/Generating/Prefab.h b/src/Generating/Prefab.h
index 5f937260d..bb961f2b3 100644
--- a/src/Generating/Prefab.h
+++ b/src/Generating/Prefab.h
@@ -32,6 +32,14 @@ class cPrefab :
 	public cPiece
 {
 public:
+	/** How to handle the space between the prefab bottom and the terrain top. */
+	enum eExtendFloorStrategy
+	{
+		efsNone,                    ///< No processing, the prefab is left "floating in the air"
+		efsRepeatBottomTillNonAir,  ///< Repeat the bottom-most block down until the first non-air block
+		efsRepeatBottomTillSolid,   ///< Repeat the bottom-most block down until the first solid block; non-solids are overwritten
+	};
+
 	struct sDef
 	{
 		int m_SizeX;
@@ -62,10 +70,9 @@ public:
 		/** The merge strategy to use while drawing the prefab. */
 		cBlockArea::eMergeStrategy m_MergeStrategy;
 
-		/** If set to true, the prefab will extend its lowermost blocks until a solid block is found,
-		thus creating a foundation for the prefab. This is used for houses to be "on the ground", as well as
-		nether fortresses not to float. */
-		bool m_ShouldExtendFloor;
+		/** How the prefab should handle not being on top of the ground.
+		This is used for houses to be "on the ground", as well as nether fortresses not to float. */
+		eExtendFloorStrategy m_ExtendFloorStrategy;
 
 		/** Chance of this piece being used, if no other modifier is active. */
 		int m_DefaultWeight;
@@ -143,8 +150,8 @@ public:
 	/** Sets the flag whether the prefab should be moved to ground level before being drawn. */
 	void SetMoveToGround(bool a_MoveToGround) { m_MoveToGround = a_MoveToGround; }
 
-	/** Sets the flag whether the lowest layer of the prefab should be repeated downwards until it hits a solid block. */
-	void SetExtendFloor(bool a_ShouldExtendFloor) { m_ShouldExtendFloor = a_ShouldExtendFloor; }
+	/** Sets the strategy to use between the bottom of the prefab and the terrain top. */
+	void SetExtendFloorStrategy(eExtendFloorStrategy a_Strategy) { m_ExtendFloorStrategy = a_Strategy; }
 
 	/** Sets the internal hitbox to the specified value. */
 	void SetHitBox(const cCuboid & a_HitBox) { m_HitBox = a_HitBox; }
@@ -183,10 +190,9 @@ protected:
 	/** The merge strategy to use when drawing the prefab into a block area */
 	cBlockArea::eMergeStrategy m_MergeStrategy;
 
-	/** If set to true, the prefab will extend its lowermost blocks until a solid block is found,
-	thus creating a foundation for the prefab. This is used for houses to be "on the ground", as well as
-	nether fortresses not to float. */
-	bool m_ShouldExtendFloor;
+	/** How the prefab should handle not being on top of the ground.
+	This is used for houses to be "on the ground", as well as nether fortresses not to float. */
+	eExtendFloorStrategy m_ExtendFloorStrategy;
 
 	/** Chance of this piece being used, if no other modifier is active. */
 	int m_DefaultWeight;
diff --git a/src/Generating/PrefabPiecePool.cpp b/src/Generating/PrefabPiecePool.cpp
index 417f8ce7e..d6c2c8819 100644
--- a/src/Generating/PrefabPiecePool.cpp
+++ b/src/Generating/PrefabPiecePool.cpp
@@ -526,16 +526,15 @@ bool cPrefabPiecePool::ReadPieceMetadataCubesetVer1(
 	}
 
 	// Get the values:
-	int AddWeightIfSame = 0, DefaultWeight = 100, MoveToGround = 0, ShouldExpandFloor = 0;
+	int AddWeightIfSame = 0, DefaultWeight = 100, MoveToGround = 0;
 	AString DepthWeight, MergeStrategy, VerticalLimit, VerticalStrategy;
-	a_LuaState.GetNamedValue("AddWeightIfSame",   AddWeightIfSame);
-	a_LuaState.GetNamedValue("DefaultWeight",     DefaultWeight);
-	a_LuaState.GetNamedValue("DepthWeight",       DepthWeight);
-	a_LuaState.GetNamedValue("MergeStrategy",     MergeStrategy);
-	a_LuaState.GetNamedValue("MoveToGround",      MoveToGround);
-	a_LuaState.GetNamedValue("ShouldExpandFloor", ShouldExpandFloor);
-	a_LuaState.GetNamedValue("VerticalLimit",     VerticalLimit);
-	a_LuaState.GetNamedValue("VerticalStrategy",  VerticalStrategy);
+	a_LuaState.GetNamedValue("AddWeightIfSame",  AddWeightIfSame);
+	a_LuaState.GetNamedValue("DefaultWeight",    DefaultWeight);
+	a_LuaState.GetNamedValue("DepthWeight",      DepthWeight);
+	a_LuaState.GetNamedValue("MergeStrategy",    MergeStrategy);
+	a_LuaState.GetNamedValue("MoveToGround",     MoveToGround);
+	a_LuaState.GetNamedValue("VerticalLimit",    VerticalLimit);
+	a_LuaState.GetNamedValue("VerticalStrategy", VerticalStrategy);
 
 	// Apply the values:
 	a_Prefab->SetAddWeightIfSame(AddWeightIfSame);
@@ -555,7 +554,42 @@ bool cPrefabPiecePool::ReadPieceMetadataCubesetVer1(
 		a_Prefab->SetMergeStrategy(strategy->second);
 	}
 	a_Prefab->SetMoveToGround(MoveToGround != 0);
-	a_Prefab->SetExtendFloor(ShouldExpandFloor != 0);
+
+	AString ExpandFloorStrategyStr;
+	if (!a_LuaState.GetNamedValue("ExpandFloorStrategy", ExpandFloorStrategyStr))
+	{
+		// Check the older variant for ExpandFloorStrategy, ShouldExpandFloor:
+		int ShouldExpandFloor;
+		if (a_LuaState.GetNamedValue("ShouldExpandFloor", ShouldExpandFloor))
+		{
+			LOG("Piece \"%s\" in file \"%s\" is using the old \"ShouldExpandFloor\" attribute. Use the new \"ExpandFloorStrategy\" attribute instead for more options.",
+				a_PieceName.c_str(), a_FileName.c_str()
+			);
+			a_Prefab->SetExtendFloorStrategy((ShouldExpandFloor != 0) ? cPrefab::efsRepeatBottomTillNonAir : cPrefab::efsNone);
+		}
+	}
+	else
+	{
+		auto lcExpandFloorStrategyStr = StrToLower(ExpandFloorStrategyStr);
+		if (lcExpandFloorStrategyStr == "repeatbottomtillnonair")
+		{
+			a_Prefab->SetExtendFloorStrategy(cPrefab::efsRepeatBottomTillNonAir);
+		}
+		else if (lcExpandFloorStrategyStr == "repeatbottomtillsolid")
+		{
+			a_Prefab->SetExtendFloorStrategy(cPrefab::efsRepeatBottomTillSolid);
+		}
+		else
+		{
+			if (lcExpandFloorStrategyStr != "none")
+			{
+				LOGWARNING("Piece \"%s\" in file \"%s\" is using an unknown \"ExpandFloorStrategy\" attribute value: \"%s\"",
+					a_PieceName.c_str(), a_FileName.c_str(), ExpandFloorStrategyStr.c_str()
+				);
+			}
+			a_Prefab->SetExtendFloorStrategy(cPrefab::efsNone);
+		}
+	}
 	if (!VerticalLimit.empty())
 	{
 		if (!a_Prefab->SetVerticalLimitFromString(VerticalLimit, a_LogWarnings))