Cavegen/Mgv5/Mgv7: Add optional giant caverns

Add to MapgenBasic for use by multiple mapgens.
Add to mgv5 and mgv7, enabled by default.

Similar to mgvalleys caverns but half the scale.
Parameters for upper y limit, distance caverns taper to full size, and
noise threshold (full cavern size).
As with mgvalleys caverns are generated first and classic caves are
disabled in any mapchunk containing a cavern, to avoid excessive
spreading volumes of liquids.
This also avoids floating blobs of liquid where a large classic cave
has overgenerated out into a neighbouring previously-generated mapchunk.

1 files changed, 43 insertions, 10 deletions

diff --git a/src/mapgen_v7.cpp b/src/mapgen_v7.cpp
index 04a9e3c16..760299fd6 100644
--- a/src/mapgen_v7.cpp
+++ b/src/mapgen_v7.cpp
@@ -41,10 +41,11 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 
 FlagDesc flagdesc_mapgen_v7[] = {
-	{"mountains",    MGV7_MOUNTAINS},
-	{"ridges",       MGV7_RIDGES},
-	{"floatlands",   MGV7_FLOATLANDS},
-	{NULL,           0}
+	{"mountains",  MGV7_MOUNTAINS},
+	{"ridges",     MGV7_RIDGES},
+	{"floatlands", MGV7_FLOATLANDS},
+	{"caverns",    MGV7_CAVERNS},
+	{NULL,         0}
 };
 
 
@@ -60,6 +61,9 @@ MapgenV7::MapgenV7(int mapgenid, MapgenV7Params *params, EmergeManager *emerge)
 	this->float_mount_height  = params->float_mount_height;
 	this->floatland_level     = params->floatland_level;
 	this->shadow_limit        = params->shadow_limit;
+	this->cavern_limit        = params->cavern_limit;
+	this->cavern_taper        = params->cavern_taper;
+	this->cavern_threshold    = params->cavern_threshold;
 
 	//// Terrain noise
 	noise_terrain_base      = new Noise(&params->np_terrain_base,      seed, csize.X, csize.Z);
@@ -76,9 +80,10 @@ MapgenV7::MapgenV7(int mapgenid, MapgenV7Params *params, EmergeManager *emerge)
 	// 1-up 1-down overgeneration
 	noise_mountain = new Noise(&params->np_mountain, seed, csize.X, csize.Y + 2, csize.Z);
 	noise_ridge    = new Noise(&params->np_ridge,    seed, csize.X, csize.Y + 2, csize.Z);
-
-	MapgenBasic::np_cave1 = params->np_cave1;
-	MapgenBasic::np_cave2 = params->np_cave2;
+	// 1 down overgeneration
+	MapgenBasic::np_cave1  = params->np_cave1;
+	MapgenBasic::np_cave2  = params->np_cave2;
+	MapgenBasic::np_cavern = params->np_cavern;
 }
 
 
@@ -100,12 +105,15 @@ MapgenV7::~MapgenV7()
 
 MapgenV7Params::MapgenV7Params()
 {
-	spflags             = MGV7_MOUNTAINS | MGV7_RIDGES;
+	spflags             = MGV7_MOUNTAINS | MGV7_RIDGES | MGV7_CAVERNS;
 	cave_width          = 0.09;
 	float_mount_density = 0.6;
 	float_mount_height  = 128.0;
 	floatland_level     = 1280;
 	shadow_limit        = 1024;
+	cavern_limit        = -256;
+	cavern_taper        = 256;
+	cavern_threshold    = 0.7;
 
 	np_terrain_base      = NoiseParams(4,    70,   v3f(600,  600,  600),  82341, 5, 0.6,  2.0);
 	np_terrain_alt       = NoiseParams(4,    25,   v3f(600,  600,  600),  5934,  5, 0.6,  2.0);
@@ -118,6 +126,7 @@ MapgenV7Params::MapgenV7Params()
 	np_float_base_height = NoiseParams(48,   24,   v3f(300,  300,  300),  907,   4, 0.7,  2.0);
 	np_mountain          = NoiseParams(-0.6, 1,    v3f(250,  350,  250),  5333,  5, 0.63, 2.0);
 	np_ridge             = NoiseParams(0,    1,    v3f(100,  100,  100),  6467,  4, 0.75, 2.0);
+	np_cavern            = NoiseParams(0,    1,    v3f(384,  128,  384),  723,   5, 0.63, 2.0);
 	np_cave1             = NoiseParams(0,    12,   v3f(61,   61,   61),   52534, 3, 0.5,  2.0);
 	np_cave2             = NoiseParams(0,    12,   v3f(67,   67,   67),   10325, 3, 0.5,  2.0);
 }
@@ -131,6 +140,9 @@ void MapgenV7Params::readParams(const Settings *settings)
 	settings->getFloatNoEx("mgv7_float_mount_height",  float_mount_height);
 	settings->getS16NoEx("mgv7_floatland_level",       floatland_level);
 	settings->getS16NoEx("mgv7_shadow_limit",          shadow_limit);
+	settings->getS16NoEx("mgv7_cavern_limit",          cavern_limit);
+	settings->getS16NoEx("mgv7_cavern_taper",          cavern_taper);
+	settings->getFloatNoEx("mgv7_cavern_threshold",    cavern_threshold);
 
 	settings->getNoiseParams("mgv7_np_terrain_base",      np_terrain_base);
 	settings->getNoiseParams("mgv7_np_terrain_alt",       np_terrain_alt);
@@ -143,6 +155,7 @@ void MapgenV7Params::readParams(const Settings *settings)
 	settings->getNoiseParams("mgv7_np_float_base_height", np_float_base_height);
 	settings->getNoiseParams("mgv7_np_mountain",          np_mountain);
 	settings->getNoiseParams("mgv7_np_ridge",             np_ridge);
+	settings->getNoiseParams("mgv7_np_cavern",            np_cavern);
 	settings->getNoiseParams("mgv7_np_cave1",             np_cave1);
 	settings->getNoiseParams("mgv7_np_cave2",             np_cave2);
 }
@@ -156,6 +169,9 @@ void MapgenV7Params::writeParams(Settings *settings) const
 	settings->setFloat("mgv7_float_mount_height",  float_mount_height);
 	settings->setS16("mgv7_floatland_level",       floatland_level);
 	settings->setS16("mgv7_shadow_limit",          shadow_limit);
+	settings->setS16("mgv7_cavern_limit",          cavern_limit);
+	settings->setS16("mgv7_cavern_taper",          cavern_taper);
+	settings->setFloat("mgv7_cavern_threshold",    cavern_threshold);
 
 	settings->setNoiseParams("mgv7_np_terrain_base",      np_terrain_base);
 	settings->setNoiseParams("mgv7_np_terrain_alt",       np_terrain_alt);
@@ -168,6 +184,7 @@ void MapgenV7Params::writeParams(Settings *settings) const
 	settings->setNoiseParams("mgv7_np_float_base_height", np_float_base_height);
 	settings->setNoiseParams("mgv7_np_mountain",          np_mountain);
 	settings->setNoiseParams("mgv7_np_ridge",             np_ridge);
+	settings->setNoiseParams("mgv7_np_cavern",            np_cavern);
 	settings->setNoiseParams("mgv7_np_cave1",             np_cave1);
 	settings->setNoiseParams("mgv7_np_cave2",             np_cave2);
 }
@@ -256,9 +273,23 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	MgStoneType stone_type = generateBiomes();
 
-	if (flags & MG_CAVES)
-		generateCaves(stone_surface_max_y, water_level);
+	// Generate caverns, tunnels and classic caves
+	if (flags & MG_CAVES) {
+		bool has_cavern = false;
+		// Generate caverns
+		if (spflags & MGV7_CAVERNS)
+			has_cavern = generateCaverns(stone_surface_max_y);
+		// Generate tunnels and classic caves
+		if (has_cavern)
+			// Disable classic 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);
+		else
+			generateCaves(stone_surface_max_y, water_level);
+	}
 
+	// Generate dungeons
 	if (flags & MG_DUNGEONS)
 		generateDungeons(stone_surface_max_y, stone_type);
 
@@ -274,8 +305,10 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 
 	//printf("makeChunk: %dms\n", t.stop());
 
+	// Update liquids
 	updateLiquid(&data->transforming_liquid, full_node_min, full_node_max);
 
+	// Calculate lighting
 	// Limit floatland shadow
 	bool propagate_shadow = !((spflags & MGV7_FLOATLANDS) &&
 		node_min.Y <= shadow_limit && node_max.Y >= shadow_limit);