Mapgen caves: Re-order generation to fix cavern bug

Previously, caverns confused tunnel generation causing biome top and filler
nodes to appear in caverns.
Split 'generateCaves()' into 2 functions to separate tunnel and large
randomwalk cave generation.
In each mapgen re-order cave generation to generate tunnels before caverns.

src/mapgen/mapgen.cpp

@@ -824,21 +824,26 @@ void MapgenBasic::dustTopNodes()
 }
 
 
-void MapgenBasic::generateCaves(s16 max_stone_y, s16 large_cave_depth)
+void MapgenBasic::generateCavesNoiseIntersection(s16 max_stone_y)
 {
-	if (max_stone_y < node_min.Y)
+	if (node_min.Y > max_stone_y)
 		return;
 
 	CavesNoiseIntersection caves_noise(ndef, m_bmgr, csize,
 		&np_cave1, &np_cave2, seed, cave_width);
 
 	caves_noise.generateCaves(vm, node_min, node_max, biomemap);
+}
 
-	if (node_max.Y > large_cave_depth)
+
+void MapgenBasic::generateCavesRandomWalk(s16 max_stone_y, s16 large_cave_depth)
+{
+	if (node_min.Y > max_stone_y || node_max.Y > large_cave_depth)
 		return;
 
 	PseudoRandom ps(blockseed + 21343);
 	u32 bruises_count = ps.range(0, 2);
+
 	for (u32 i = 0; i < bruises_count; i++) {
 		CavesRandomWalk cave(ndef, &gennotify, seed, water_level,
 			c_water_source, c_lava_source, lava_depth, biomegen);
@@ -849,7 +854,7 @@ void MapgenBasic::generateCaves(s16 max_stone_y, s16 large_cave_depth)
 }
 
 
-bool MapgenBasic::generateCaverns(s16 max_stone_y)
+bool MapgenBasic::generateCavernsNoise(s16 max_stone_y)
 {
 	if (node_min.Y > max_stone_y || node_min.Y > cavern_limit)
 		return false;

src/mapgen/mapgen.h

@@ -238,11 +238,12 @@ public:
 	MapgenBasic(int mapgenid, MapgenParams *params, EmergeManager *emerge);
 	virtual ~MapgenBasic();
 
-	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);
 	virtual void generateBiomes();
 	virtual void dustTopNodes();
+	virtual void generateCavesNoiseIntersection(s16 max_stone_y);
+	virtual void generateCavesRandomWalk(s16 max_stone_y, s16 large_cave_depth);
+	virtual bool generateCavernsNoise(s16 max_stone_y);
+	virtual void generateDungeons(s16 max_stone_y);
 
 protected:
 	EmergeManager *m_emerge;

src/mapgen/mapgen_carpathian.cpp

@@ -250,20 +250,25 @@ void MapgenCarpathian::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	generateBiomes();
 
-	// Generate caverns, tunnels and classic caves
+	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
-		bool has_cavern = false;
+		// Generate tunnels first as caverns confuse them
+		generateCavesNoiseIntersection(stone_surface_max_y);
+
 		// Generate caverns
+		bool near_cavern = false;
 		if (spflags & MGCARPATHIAN_CAVERNS)
-			has_cavern = generateCaverns(stone_surface_max_y);
-		// Generate tunnels and classic caves
-		if (has_cavern)
-			// Disable classic caves in this mapchunk by setting
+			near_cavern = generateCavernsNoise(stone_surface_max_y);
+
+		// Generate large randomwalk caves
+		if (near_cavern)
+			// Disable large randomwalk caves in this mapchunk by setting
 			// 'large cave depth' to world base. Avoids excessive liquid in
 			// large caverns and floating blobs of overgenerated liquid.
-			generateCaves(stone_surface_max_y, -MAX_MAP_GENERATION_LIMIT);
+			generateCavesRandomWalk(stone_surface_max_y,
+				-MAX_MAP_GENERATION_LIMIT);
 		else
-			generateCaves(stone_surface_max_y, large_cave_depth);
+			generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
 	}
 
 	// Generate dungeons

src/mapgen/mapgen_flat.cpp

@@ -198,8 +198,12 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	generateBiomes();
 
-	if (flags & MG_CAVES)
-		generateCaves(stone_surface_max_y, large_cave_depth);
+	if (flags & MG_CAVES) {
+		// Generate tunnels
+		generateCavesNoiseIntersection(stone_surface_max_y);
+		// Generate large randomwalk caves
+		generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
+	}
 
 	if ((flags & MG_DUNGEONS) && full_node_min.Y >= dungeon_ymin &&
 			full_node_max.Y <= dungeon_ymax)

src/mapgen/mapgen_fractal.cpp

@@ -209,8 +209,12 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	generateBiomes();
 
-	if (flags & MG_CAVES)
-		generateCaves(stone_surface_max_y, large_cave_depth);
+	if (flags & MG_CAVES) {
+		// Generate tunnels
+		generateCavesNoiseIntersection(stone_surface_max_y);
+		// Generate large randomwalk caves
+		generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
+	}
 
 	if ((flags & MG_DUNGEONS) && full_node_min.Y >= dungeon_ymin &&
 			full_node_max.Y <= dungeon_ymax)

src/mapgen/mapgen_v5.cpp

@@ -209,20 +209,25 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	generateBiomes();
 
-	// Generate caverns, tunnels and classic caves
+	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
-		bool near_cavern = false;
+		// Generate tunnels first as caverns confuse them
+		generateCavesNoiseIntersection(stone_surface_max_y);
+
 		// Generate caverns
+		bool near_cavern = false;
 		if (spflags & MGV5_CAVERNS)
-			near_cavern = generateCaverns(stone_surface_max_y);
-		// Generate tunnels and classic caves
+			near_cavern = generateCavernsNoise(stone_surface_max_y);
+
+		// Generate large randomwalk caves
 		if (near_cavern)
-			// Disable classic caves in this mapchunk by setting
+			// Disable large randomwalk caves in this mapchunk by setting
 			// 'large cave depth' to world base. Avoids excessive liquid in
 			// large caverns and floating blobs of overgenerated liquid.
-			generateCaves(stone_surface_max_y, -MAX_MAP_GENERATION_LIMIT);
+			generateCavesRandomWalk(stone_surface_max_y,
+				-MAX_MAP_GENERATION_LIMIT);
 		else
-			generateCaves(stone_surface_max_y, large_cave_depth);
+			generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
 	}
 
 	// Generate dungeons and desert temples

src/mapgen/mapgen_v7.cpp

@@ -313,20 +313,25 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	generateBiomes();
 
-	// Generate caverns, tunnels and classic caves
+	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
-		bool near_cavern = false;
+		// Generate tunnels first as caverns confuse them
+		generateCavesNoiseIntersection(stone_surface_max_y);
+
 		// Generate caverns
+		bool near_cavern = false;
 		if (spflags & MGV7_CAVERNS)
-			near_cavern = generateCaverns(stone_surface_max_y);
-		// Generate tunnels and classic caves
+			near_cavern = generateCavernsNoise(stone_surface_max_y);
+
+		// Generate large randomwalk caves
 		if (near_cavern)
-			// Disable classic caves in this mapchunk by setting
+			// Disable large randomwalk caves in this mapchunk by setting
 			// 'large cave depth' to world base. Avoids excessive liquid in
 			// large caverns and floating blobs of overgenerated liquid.
-			generateCaves(stone_surface_max_y, -MAX_MAP_GENERATION_LIMIT);
+			generateCavesRandomWalk(stone_surface_max_y,
+				-MAX_MAP_GENERATION_LIMIT);
 		else
-			generateCaves(stone_surface_max_y, large_cave_depth);
+			generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
 	}
 
 	// Generate dungeons

src/mapgen/mapgen_valleys.cpp

@@ -233,18 +233,23 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 	// Place biome-specific nodes and build biomemap
 	generateBiomes();
 
-	// Generate caverns, tunnels and classic caves
+	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
+		// Generate tunnels first as caverns confuse them
+		generateCavesNoiseIntersection(stone_surface_max_y);
+
 		// Generate caverns
-		bool near_cavern = generateCaverns(stone_surface_max_y);
-		// Generate tunnels and classic caves
+		bool near_cavern = generateCavernsNoise(stone_surface_max_y);
+
+		// Generate large randomwalk caves
 		if (near_cavern)
-			// Disable classic caves in this mapchunk by setting
+			// Disable large randomwalk caves in this mapchunk by setting
 			// 'large cave depth' to world base. Avoids excessive liquid in
 			// large caverns and floating blobs of overgenerated liquid.
-			generateCaves(stone_surface_max_y, -MAX_MAP_GENERATION_LIMIT);
+			generateCavesRandomWalk(stone_surface_max_y,
+				-MAX_MAP_GENERATION_LIMIT);
 		else
-			generateCaves(stone_surface_max_y, large_cave_depth);
+			generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
 	}
 
 	// Dungeon creation