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, 47 insertions, 39 deletions

diff --git a/src/mapgen_v5.cpp b/src/mapgen_v5.cpp
index 9f189e253..b983026e6 100644
--- a/src/mapgen_v5.cpp
+++ b/src/mapgen_v5.cpp
@@ -41,15 +41,19 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 
 FlagDesc flagdesc_mapgen_v5[] = {
-	{NULL,         0}
+	{"caverns", MGV5_CAVERNS},
+	{NULL,      0}
 };
 
 
 MapgenV5::MapgenV5(int mapgenid, MapgenV5Params *params, EmergeManager *emerge)
 	: MapgenBasic(mapgenid, params, emerge)
 {
-	this->spflags    = params->spflags;
-	this->cave_width = params->cave_width;
+	this->spflags          = params->spflags;
+	this->cave_width       = params->cave_width;
+	this->cavern_limit     = params->cavern_limit;
+	this->cavern_taper     = params->cavern_taper;
+	this->cavern_threshold = params->cavern_threshold;
 
 	// Terrain noise
 	noise_filler_depth = new Noise(&params->np_filler_depth, seed, csize.X, csize.Z);
@@ -59,9 +63,10 @@ MapgenV5::MapgenV5(int mapgenid, MapgenV5Params *params, EmergeManager *emerge)
 	// 3D terrain noise
 	// 1-up 1-down overgeneration
 	noise_ground = new Noise(&params->np_ground, 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;
 }
 
 
@@ -76,47 +81,55 @@ MapgenV5::~MapgenV5()
 
 MapgenV5Params::MapgenV5Params()
 {
-	spflags    = 0;
-	cave_width = 0.125;
+	spflags          = MGV5_CAVERNS;
+	cave_width       = 0.125;
+	cavern_limit     = -256;
+	cavern_taper     = 256;
+	cavern_threshold = 0.7;
 
 	np_filler_depth = NoiseParams(0, 1,  v3f(150, 150, 150), 261,    4, 0.7,  2.0);
 	np_factor       = NoiseParams(0, 1,  v3f(250, 250, 250), 920381, 3, 0.45, 2.0);
 	np_height       = NoiseParams(0, 10, v3f(250, 250, 250), 84174,  4, 0.5,  2.0);
+	np_ground       = NoiseParams(0, 40, v3f(80,  80,  80),  983240, 4, 0.55, 2.0, NOISE_FLAG_EASED);
 	np_cave1        = NoiseParams(0, 12, v3f(50,  50,  50),  52534,  4, 0.5,  2.0);
 	np_cave2        = NoiseParams(0, 12, v3f(50,  50,  50),  10325,  4, 0.5,  2.0);
-	np_ground       = NoiseParams(0, 40, v3f(80,  80,  80),  983240, 4, 0.55, 2.0, NOISE_FLAG_EASED);
+	np_cavern       = NoiseParams(0, 1,  v3f(384, 128, 384), 723,    5, 0.63, 2.0);
 }
 
 
-//#define CAVE_NOISE_SCALE 12.0
-//#define CAVE_NOISE_THRESHOLD (1.5/CAVE_NOISE_SCALE) = 0.125
-
-
 void MapgenV5Params::readParams(const Settings *settings)
 {
-	settings->getFlagStrNoEx("mgv5_spflags",  spflags, flagdesc_mapgen_v5);
-	settings->getFloatNoEx("mgv5_cave_width", cave_width);
+	settings->getFlagStrNoEx("mgv5_spflags",        spflags, flagdesc_mapgen_v5);
+	settings->getFloatNoEx("mgv5_cave_width",       cave_width);
+	settings->getS16NoEx("mgv5_cavern_limit",       cavern_limit);
+	settings->getS16NoEx("mgv5_cavern_taper",       cavern_taper);
+	settings->getFloatNoEx("mgv5_cavern_threshold", cavern_threshold);
 
 	settings->getNoiseParams("mgv5_np_filler_depth", np_filler_depth);
 	settings->getNoiseParams("mgv5_np_factor",       np_factor);
 	settings->getNoiseParams("mgv5_np_height",       np_height);
+	settings->getNoiseParams("mgv5_np_ground",       np_ground);
 	settings->getNoiseParams("mgv5_np_cave1",        np_cave1);
 	settings->getNoiseParams("mgv5_np_cave2",        np_cave2);
-	settings->getNoiseParams("mgv5_np_ground",       np_ground);
+	settings->getNoiseParams("mgv5_np_cavern",       np_cavern);
 }
 
 
 void MapgenV5Params::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgv5_spflags",  spflags, flagdesc_mapgen_v5, U32_MAX);
-	settings->setFloat("mgv5_cave_width", cave_width);
+	settings->setFlagStr("mgv5_spflags",        spflags, flagdesc_mapgen_v5, U32_MAX);
+	settings->setFloat("mgv5_cave_width",       cave_width);
+	settings->setS16("mgv5_cavern_limit",       cavern_limit);
+	settings->setS16("mgv5_cavern_taper",       cavern_taper);
+	settings->setFloat("mgv5_cavern_threshold", cavern_threshold);
 
 	settings->setNoiseParams("mgv5_np_filler_depth", np_filler_depth);
 	settings->setNoiseParams("mgv5_np_factor",       np_factor);
 	settings->setNoiseParams("mgv5_np_height",       np_height);
+	settings->setNoiseParams("mgv5_np_ground",       np_ground);
 	settings->setNoiseParams("mgv5_np_cave1",        np_cave1);
 	settings->setNoiseParams("mgv5_np_cave2",        np_cave2);
-	settings->setNoiseParams("mgv5_np_ground",       np_ground);
+	settings->setNoiseParams("mgv5_np_cavern",       np_cavern);
 }
 
 
@@ -190,9 +203,21 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 	biomegen->calcBiomeNoise(node_min);
 	MgStoneType stone_type = generateBiomes();
 
-	// Generate caves
-	if ((flags & MG_CAVES) && (stone_surface_max_y >= node_min.Y))
-		generateCaves(stone_surface_max_y, MGV5_LARGE_CAVE_DEPTH);
+	// Generate caverns, tunnels and classic caves
+	if (flags & MG_CAVES) {
+		bool has_cavern = false;
+		// Generate caverns
+		if (spflags & MGV5_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, MGV5_LARGE_CAVE_DEPTH);
+	}
 
 	// Generate dungeons and desert temples
 	if (flags & MG_DUNGEONS)
@@ -223,23 +248,6 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 }
 
 
-//bool is_cave(u32 index) {
-//	double d1 = contour(noise_cave1->result[index]);
-//	double d2 = contour(noise_cave2->result[index]);
-//	return d1*d2 > CAVE_NOISE_THRESHOLD;
-//}
-
-//bool val_is_ground(v3s16 p, u32 index, u32 index2d) {
-//	double f = 0.55 + noise_factor->result[index2d];
-//	if(f < 0.01)
-//		f = 0.01;
-//	else if(f >= 1.0)
-//		f *= 1.6;
-//	double h = WATER_LEVEL + 10 * noise_height->result[index2d];
-//	return (noise_ground->result[index] * f > (double)p.Y - h);
-//}
-
-
 int MapgenV5::generateBaseTerrain()
 {
 	u32 index = 0;