Biomes/decorations/ores: Make relative to 'water_level' setting

Add 'biome_zero_level' argument to 'generateBiomes()', 'deco_zero_level'
argument to 'placeAllDecos()' and 'ore_zero_level' to 'placeAllOres()'
to allow mapgens to vertically shift the registered biomes, decorations
and ores per-mapchunk.
Will also allow many realm possibilities in future mapgens.

14 files changed, 90 insertions, 43 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 3fc815272..e675cc703 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -4420,6 +4420,9 @@ Definition tables
     --  ^ In this example, there is a 3x3x3 cluster where 8 out of the 27 nodes are coal ore
         y_min = -31000,
         y_max = 64,
+    --  ^ Lower and upper limits for ore.
+    --  ^ Limits are relative to y = water_level - 1 for core mapgen, or
+    --  ^ relative to y = 0 for minetest.generate_ores().
         flags = "",
     --  ^ Attributes for this ore generation
         noise_threshold = 0.5,
@@ -4429,7 +4432,7 @@ Definition tables
     --  ^ Needed for sheet ore_type.  Omit from scatter ore_type for a uniform ore distribution
         random_factor = 1.0,
     --  ^ Multiplier of the randomness contribution to the noise value at any
-    --   given point to decide if ore should be placed.  Set to 0 for solid veins.
+    --  ^ given point to decide if ore should be placed.  Set to 0 for solid veins.
     --  ^ This parameter is only valid for ore_type == "vein".
         biomes = {"desert", "rainforest"}
     --  ^ List of biomes in which this decoration occurs.  Occurs in all biomes if this is omitted,
@@ -4467,6 +4470,7 @@ The Biome API is still in an experimental phase and subject to change.
         y_min = 1,
         y_max = 31000,
     --  ^ Lower and upper limits for biome.
+    --  ^ Limits are relative to y = water_level - 1.
     --  ^ Because biome is not recalculated for every node in a node column
     --  ^ some biome materials can exceed their limits, especially stone.
     --  ^ For each node column in a mapchunk, biome is only recalculated at column
@@ -4509,9 +4513,11 @@ The Biome API is still in an experimental phase and subject to change.
     --  ^ Can be a list of (or a single) biome names, IDs, or definitions.
         y_min = -31000
         y_max = 31000
-    -- ^ Minimum and maximum `y` positions these decorations can be generated at.
-    -- ^ This parameter refers to the `y` position of the decoration base, so
-    --   the actual maximum height would be `height_max + size.Y`.
+    --  ^ Lower and upper limits for decoration.
+    --  ^ Limits are relative to y = water_level - 1 for core mapgen, or
+    --  ^ relative to y = 0 for minetest.generate_decorations().
+    --  ^ This parameter refers to the `y` position of the decoration base, so
+    --    the actual maximum height would be `height_max + size.Y`.
         spawn_by = "default:water",
     --  ^ Node (or list of nodes) that the decoration only spawns next to.
     --  ^ Checks two horizontal planes of neighbouring nodes (including diagonal neighbours),
diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index b095d34c8..7a03a4606 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -621,7 +621,7 @@ MapgenBasic::~MapgenBasic()
 }
 
 
-MgStoneType MapgenBasic::generateBiomes()
+MgStoneType MapgenBasic::generateBiomes(s16 biome_zero_level)
 {
 	// can't generate biomes without a biome generator!
 	assert(biomegen);
@@ -673,7 +673,10 @@ MgStoneType MapgenBasic::generateBiomes()
 				(air_above || !biome);
 
 			if (is_stone_surface || is_water_surface) {
-				biome = biomegen->getBiomeAtIndex(index, y);
+				// Limit to +-MAX MAP GENERATION LIMIT to work with biome y_min / y_max.
+				s32 relative_y = rangelim(y - biome_zero_level,
+					-MAX_MAP_GENERATION_LIMIT, MAX_MAP_GENERATION_LIMIT);
+				biome = biomegen->getBiomeAtIndex(index, relative_y);
 
 				if (biomemap[index] == BIOME_NONE && is_stone_surface)
 					biomemap[index] = biome->index;
diff --git a/src/mapgen.h b/src/mapgen.h
index 7acceddaf..7f4b76c3e 100644
--- a/src/mapgen.h
+++ b/src/mapgen.h
@@ -251,7 +251,7 @@ public:
 	virtual void generateCaves(s16 max_stone_y, s16 large_cave_depth);
 	virtual bool generateCaverns(s16 max_stone_y);
 	virtual void generateDungeons(s16 max_stone_y, MgStoneType stone_type);
-	virtual MgStoneType generateBiomes();
+	virtual MgStoneType generateBiomes(s16 biome_zero_level = 0);
 	virtual void dustTopNodes();
 
 protected:
diff --git a/src/mapgen_carpathian.cpp b/src/mapgen_carpathian.cpp
index c33239087..598795830 100644
--- a/src/mapgen_carpathian.cpp
+++ b/src/mapgen_carpathian.cpp
@@ -242,7 +242,7 @@ void MapgenCarpathian::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	// Generate caverns, tunnels and classic caves
 	if (flags & MG_CAVES) {
@@ -266,10 +266,12 @@ void MapgenCarpathian::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
@@ -448,4 +450,4 @@ int MapgenCarpathian::generateTerrain()
 	}
 
 	return stone_surface_max_y;
-}
\ No newline at end of file
+}
diff --git a/src/mapgen_flat.cpp b/src/mapgen_flat.cpp
index 95fb35412..56dca1f06 100644
--- a/src/mapgen_flat.cpp
+++ b/src/mapgen_flat.cpp
@@ -189,7 +189,7 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	if (flags & MG_CAVES)
 		generateCaves(stone_surface_max_y, large_cave_depth);
@@ -199,10 +199,12 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
diff --git a/src/mapgen_fractal.cpp b/src/mapgen_fractal.cpp
index 4fe0d8369..13da2f180 100644
--- a/src/mapgen_fractal.cpp
+++ b/src/mapgen_fractal.cpp
@@ -199,7 +199,7 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	if (flags & MG_CAVES)
 		generateCaves(stone_surface_max_y, large_cave_depth);
@@ -209,10 +209,12 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
diff --git a/src/mapgen_v5.cpp b/src/mapgen_v5.cpp
index ffa1f538c..ad1e9d0a5 100644
--- a/src/mapgen_v5.cpp
+++ b/src/mapgen_v5.cpp
@@ -200,7 +200,7 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	// Generate caverns, tunnels and classic caves
 	if (flags & MG_CAVES) {
@@ -224,10 +224,12 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
diff --git a/src/mapgen_v6.cpp b/src/mapgen_v6.cpp
index ebbd932d4..e8e0c583d 100644
--- a/src/mapgen_v6.cpp
+++ b/src/mapgen_v6.cpp
@@ -619,10 +619,12 @@ void MapgenV6::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Calculate lighting
 	if (flags & MG_LIGHT)
diff --git a/src/mapgen_v7.cpp b/src/mapgen_v7.cpp
index 17f2df835..4b263bdb3 100644
--- a/src/mapgen_v7.cpp
+++ b/src/mapgen_v7.cpp
@@ -298,7 +298,7 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	// Generate caverns, tunnels and classic caves
 	if (flags & MG_CAVES) {
@@ -322,10 +322,12 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
diff --git a/src/mapgen_valleys.cpp b/src/mapgen_valleys.cpp
index 71c0b001f..8c54dbcd9 100644
--- a/src/mapgen_valleys.cpp
+++ b/src/mapgen_valleys.cpp
@@ -236,7 +236,7 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Place biome-specific nodes and build biomemap
-	MgStoneType stone_type = generateBiomes();
+	MgStoneType stone_type = generateBiomes(water_level - 1);
 
 	// Cave creation.
 	if (flags & MG_CAVES)
@@ -248,10 +248,12 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 
 	// Generate the registered decorations
 	if (flags & MG_DECORATIONS)
-		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);
+		m_emerge->decomgr->placeAllDecos(this, blockseed,
+			node_min, node_max, water_level - 1);
 
 	// Generate the registered ores
-	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
+	m_emerge->oremgr->placeAllOres(this, blockseed,
+		node_min, node_max, water_level - 1);
 
 	// Sprinkle some dust on top after everything else was generated
 	dustTopNodes();
diff --git a/src/mg_decoration.cpp b/src/mg_decoration.cpp
index b13ddbadb..4af7a7897 100644
--- a/src/mg_decoration.cpp
+++ b/src/mg_decoration.cpp
@@ -48,7 +48,7 @@ DecorationManager::DecorationManager(IGameDef *gamedef) :
 
 
 size_t DecorationManager::placeAllDecos(Mapgen *mg, u32 blockseed,
-	v3s16 nmin, v3s16 nmax)
+	v3s16 nmin, v3s16 nmax, s16 deco_zero_level)
 {
 	size_t nplaced = 0;
 
@@ -57,7 +57,7 @@ size_t DecorationManager::placeAllDecos(Mapgen *mg, u32 blockseed,
 		if (!deco)
 			continue;
 
-		nplaced += deco->placeDeco(mg, blockseed, nmin, nmax);
+		nplaced += deco->placeDeco(mg, blockseed, nmin, nmax, deco_zero_level);
 		blockseed++;
 	}
 
@@ -123,8 +123,18 @@ bool Decoration::canPlaceDecoration(MMVManip *vm, v3s16 p)
 }
 
 
-size_t Decoration::placeDeco(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax)
+size_t Decoration::placeDeco(Mapgen *mg, u32 blockseed,
+	v3s16 nmin, v3s16 nmax, s16 deco_zero_level)
 {
+	// Decoration y_min / y_max is displaced by deco_zero_level or remains
+	// unchanged. Any decoration with a limit at +-MAX_MAP_GENERATION_LIMIT is
+	// considered to have that limit at +-infinity, so we do not alter that limit.
+	s32 y_min_disp = (y_min <= -MAX_MAP_GENERATION_LIMIT) ?
+		-MAX_MAP_GENERATION_LIMIT : y_min + deco_zero_level;
+
+	s32 y_max_disp = (y_max >= MAX_MAP_GENERATION_LIMIT) ?
+		MAX_MAP_GENERATION_LIMIT : y_max + deco_zero_level;
+
 	PcgRandom ps(blockseed + 53);
 	int carea_size = nmax.X - nmin.X + 1;
 
@@ -179,8 +189,7 @@ size_t Decoration::placeDeco(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax)
 			else
 				y = mg->findGroundLevel(v2s16(x, z), nmin.Y, nmax.Y);
 
-			if (y < nmin.Y || y > nmax.Y ||
-				y < y_min  || y > y_max)
+			if (y < y_min_disp || y > y_max_disp || y < nmin.Y || y > nmax.Y)
 				continue;
 
 			if (y + getHeight() > mg->vm->m_area.MaxEdge.Y) {
diff --git a/src/mg_decoration.h b/src/mg_decoration.h
index 968c78612..a7fdb97fe 100644
--- a/src/mg_decoration.h
+++ b/src/mg_decoration.h
@@ -70,7 +70,8 @@ public:
 	virtual void resolveNodeNames();
 
 	bool canPlaceDecoration(MMVManip *vm, v3s16 p);
-	size_t placeDeco(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax);
+	size_t placeDeco(Mapgen *mg, u32 blockseed,
+		v3s16 nmin, v3s16 nmax, s16 deco_zero_level);
 	//size_t placeCutoffs(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax);
 
 	virtual size_t generate(MMVManip *vm, PcgRandom *pr, v3s16 p) = 0;
@@ -145,7 +146,8 @@ public:
 		}
 	}
 
-	size_t placeAllDecos(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax);
+	size_t placeAllDecos(Mapgen *mg, u32 blockseed,
+		v3s16 nmin, v3s16 nmax, s16 deco_zero_level = 0);
 };
 
 #endif
diff --git a/src/mg_ore.cpp b/src/mg_ore.cpp
index 73af2e2e6..36100f762 100644
--- a/src/mg_ore.cpp
+++ b/src/mg_ore.cpp
@@ -43,7 +43,8 @@ OreManager::OreManager(IGameDef *gamedef) :
 }
 
 
-size_t OreManager::placeAllOres(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax)
+size_t OreManager::placeAllOres(Mapgen *mg, u32 blockseed,
+	v3s16 nmin, v3s16 nmax, s16 ore_zero_level)
 {
 	size_t nplaced = 0;
 
@@ -52,7 +53,7 @@ size_t OreManager::placeAllOres(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nma
 		if (!ore)
 			continue;
 
-		nplaced += ore->placeOre(mg, blockseed, nmin, nmax);
+		nplaced += ore->placeOre(mg, blockseed, nmin, nmax, ore_zero_level);
 		blockseed++;
 	}
 
@@ -85,13 +86,23 @@ void Ore::resolveNodeNames()
 }
 
 
-size_t Ore::placeOre(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax)
+size_t Ore::placeOre(Mapgen *mg, u32 blockseed,
+	v3s16 nmin, v3s16 nmax, s16 ore_zero_level)
 {
-	if (!(nmin.Y <= y_max && nmax.Y >= y_min))
+	// Ore y_min / y_max is displaced by ore_zero_level or remains unchanged.
+	// Any ore with a limit at +-MAX_MAP_GENERATION_LIMIT is considered to have
+	// that limit at +-infinity, so we do not alter that limit.
+	s32 y_min_disp = (y_min <= -MAX_MAP_GENERATION_LIMIT) ?
+		-MAX_MAP_GENERATION_LIMIT : y_min + ore_zero_level;
+
+	s32 y_max_disp = (y_max >= MAX_MAP_GENERATION_LIMIT) ?
+		MAX_MAP_GENERATION_LIMIT : y_max + ore_zero_level;
+
+	if (nmin.Y > y_max_disp || nmax.Y < y_min_disp)
 		return 0;
 
-	int actual_ymin = MYMAX(nmin.Y, y_min);
-	int actual_ymax = MYMIN(nmax.Y, y_max);
+	int actual_ymin = MYMAX(nmin.Y, y_min_disp);
+	int actual_ymax = MYMIN(nmax.Y, y_max_disp);
 	if (clust_size >= actual_ymax - actual_ymin + 1)
 		return 0;
 
diff --git a/src/mg_ore.h b/src/mg_ore.h
index 5aeb3631c..692cd848e 100644
--- a/src/mg_ore.h
+++ b/src/mg_ore.h
@@ -70,7 +70,8 @@ public:
 
 	virtual void resolveNodeNames();
 
-	size_t placeOre(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax);
+	size_t placeOre(Mapgen *mg, u32 blockseed,
+		v3s16 nmin, v3s16 nmax, s16 ore_zero_level);
 	virtual void generate(MMVManip *vm, int mapseed, u32 blockseed,
 		v3s16 nmin, v3s16 nmax, u8 *biomemap) = 0;
 };
@@ -163,7 +164,8 @@ public:
 
 	void clear();
 
-	size_t placeAllOres(Mapgen *mg, u32 blockseed, v3s16 nmin, v3s16 nmax);
+	size_t placeAllOres(Mapgen *mg, u32 blockseed,
+		v3s16 nmin, v3s16 nmax, s16 ore_zero_level = 0);
 };
 
 #endif