Mapgen flags: Add 'biomes' global mapgen flag (#7355)

Previously the only way to disable biomes was to 'clear' the registered
biomes in a mod, but this method causes large amounts of unnecessary
processing:
1. Calculation of 4 2D noises.
2. Looping through all nodes of a mapchunk replacing nodes with identical
nodes.
The new flag disables those operations.

builtin/settingtypes.txt

@@ -1282,7 +1282,7 @@ mapgen_limit (Map generation limit) int 31000 0 31000
 #    and junglegrass, in all other mapgens this flag controls all decorations.
 #    Flags that are not enabled are not modified from the default.
 #    Flags starting with 'no' are used to explicitly disable them.
-mg_flags (Mapgen flags) flags caves,dungeons,light,decorations caves,dungeons,light,decorations,nocaves,nodungeons,nolight,nodecorations
+mg_flags (Mapgen flags) flags caves,dungeons,light,decorations,biomes caves,dungeons,light,decorations,biomes,nocaves,nodungeons,nolight,nodecorations,nobiomes
 
 #    Whether dungeons occasionally project from the terrain.
 projecting_dungeons (Projecting dungeons) bool true

src/mapgen/mapgen.cpp

@@ -56,7 +56,8 @@ FlagDesc flagdesc_mapgen[] = {
 	{"dungeons",    MG_DUNGEONS},
 	{"light",       MG_LIGHT},
 	{"decorations", MG_DECORATIONS},
-	{NULL,       0}
+	{"biomes",      MG_BIOMES},
+	{NULL,          0}
 };
 
 FlagDesc flagdesc_gennotify[] = {

src/mapgen/mapgen.h

@@ -36,6 +36,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define MG_FLAT        0x08  // Deprecated. Moved into mgv6 flags
 #define MG_LIGHT       0x10
 #define MG_DECORATIONS 0x20
+#define MG_BIOMES      0x40
 
 typedef u8 biome_t;  // copy from mg_biome.h to avoid an unnecessary include
 
@@ -122,7 +123,7 @@ struct MapgenParams {
 	u64 seed = 0;
 	s16 water_level = 1;
 	s16 mapgen_limit = MAX_MAP_GENERATION_LIMIT;
-	u32 flags = MG_CAVES | MG_LIGHT | MG_DECORATIONS;
+	u32 flags = MG_CAVES | MG_LIGHT | MG_DECORATIONS | MG_BIOMES;
 
 	BiomeParams *bparams = nullptr;
 

src/mapgen/mapgen_carpathian.cpp

@@ -247,8 +247,10 @@ void MapgenCarpathian::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
-	biomegen->calcBiomeNoise(node_min);
-	generateBiomes();
+	if (flags & MG_BIOMES) {
+		biomegen->calcBiomeNoise(node_min);
+		generateBiomes();
+	}
 
 	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
@@ -284,7 +286,8 @@ void MapgenCarpathian::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	// Update liquids
 	updateLiquid(&data->transforming_liquid, full_node_min, full_node_max);

src/mapgen/mapgen_flat.cpp

@@ -195,8 +195,10 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
-	biomegen->calcBiomeNoise(node_min);
-	generateBiomes();
+	if (flags & MG_BIOMES) {
+		biomegen->calcBiomeNoise(node_min);
+		generateBiomes();
+	}
 
 	if (flags & MG_CAVES) {
 		// Generate tunnels
@@ -217,7 +219,8 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	//printf("makeChunk: %dms\n", t.stop());
 

src/mapgen/mapgen_fractal.cpp

@@ -206,8 +206,10 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
-	biomegen->calcBiomeNoise(node_min);
-	generateBiomes();
+	if (flags & MG_BIOMES) {
+		biomegen->calcBiomeNoise(node_min);
+		generateBiomes();
+	}
 
 	if (flags & MG_CAVES) {
 		// Generate tunnels
@@ -228,7 +230,8 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	//printf("makeChunk: %dms\n", t.stop());
 

src/mapgen/mapgen_v5.cpp

@@ -206,8 +206,10 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
-	biomegen->calcBiomeNoise(node_min);
-	generateBiomes();
+	if (flags & MG_BIOMES) {
+		biomegen->calcBiomeNoise(node_min);
+		generateBiomes();
+	}
 
 	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
@@ -243,7 +245,8 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	//printf("makeChunk: %dms\n", t.stop());
 

src/mapgen/mapgen_v7.cpp

@@ -326,8 +326,10 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
-	biomegen->calcBiomeNoise(node_min);
-	generateBiomes();
+	if (flags & MG_BIOMES) {
+		biomegen->calcBiomeNoise(node_min);
+		generateBiomes();
+	}
 
 	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
@@ -363,7 +365,8 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	// Update liquids
 	updateLiquid(&data->transforming_liquid, full_node_min, full_node_max);

src/mapgen/mapgen_valleys.cpp

@@ -231,7 +231,8 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 	updateHeightmap(node_min, node_max);
 
 	// Place biome-specific nodes and build biomemap
-	generateBiomes();
+	if (flags & MG_BIOMES)
+		generateBiomes();
 
 	// Generate tunnels, caverns and large randomwalk caves
 	if (flags & MG_CAVES) {
@@ -265,7 +266,8 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);
 
 	// Sprinkle some dust on top after everything else was generated
-	dustTopNodes();
+	if (flags & MG_BIOMES)
+		dustTopNodes();
 
 	updateLiquid(&data->transforming_liquid, full_node_min, full_node_max);
 

src/mapgen/mg_biome.cpp

@@ -192,7 +192,12 @@ BiomeGenOriginal::BiomeGenOriginal(BiomeManager *biomemgr,
 
 	heatmap  = noise_heat->result;
 	humidmap = noise_humidity->result;
+
 	biomemap = new biome_t[m_csize.X * m_csize.Z];
+	// Initialise with the ID of the default biome so that cavegen can get
+	// biomes when biome generation (which calculates the biomemap IDs) is
+	// disabled.
+	memset(biomemap, 0, sizeof(biome_t) * m_csize.X * m_csize.Z);
 }
 
 BiomeGenOriginal::~BiomeGenOriginal()