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, 9 insertions, 1 deletions

diff --git a/src/mapgen_v5.h b/src/mapgen_v5.h
index ddb090a9c..034d53560 100644
--- a/src/mapgen_v5.h
+++ b/src/mapgen_v5.h
@@ -25,6 +25,9 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #define MGV5_LARGE_CAVE_DEPTH -256
 
+///////// Mapgen V5 flags
+#define MGV5_CAVERNS 0x01
+
 class BiomeManager;
 
 extern FlagDesc flagdesc_mapgen_v5[];
@@ -33,12 +36,17 @@ extern FlagDesc flagdesc_mapgen_v5[];
 struct MapgenV5Params : public MapgenParams {
 	u32 spflags;
 	float cave_width;
+	s16 cavern_limit;
+	s16 cavern_taper;
+	float cavern_threshold;
+
 	NoiseParams np_filler_depth;
 	NoiseParams np_factor;
 	NoiseParams np_height;
+	NoiseParams np_ground;
 	NoiseParams np_cave1;
 	NoiseParams np_cave2;
-	NoiseParams np_ground;
+	NoiseParams np_cavern;
 
 	MapgenV5Params();
 	~MapgenV5Params() {}