From fe4ce03d529f70346b2e2c4872223ebdcd37fffa Mon Sep 17 00:00:00 2001
From: kwolekr <kwolekr@minetest.net>
Date: Mon, 1 Jul 2013 21:10:59 -0400
Subject: [PATCH] Cavegen: Prevent caves from occuring above ground level, and
 superfluous mixing of lava and water in caves

---
 src/cavegen.cpp | 21 +++++++++++++++++++--
 src/cavegen.h   |  2 ++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/cavegen.cpp b/src/cavegen.cpp
index 8e6798586..01149084b 100644
--- a/src/cavegen.cpp
+++ b/src/cavegen.cpp
@@ -24,6 +24,12 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "mapgen_v7.h"
 #include "cavegen.h"
 
+NoiseParams nparams_caveliquids =
+	{0, 1, v3f(150.0, 150.0, 150.0), 776, 3, 0.6};
+
+
+///////////////////////////////////////////////////////////////////////////////
+
 
 CaveV6::CaveV6(MapgenV6 *mg, PseudoRandom *ps, PseudoRandom *ps2, bool is_large_cave) {
 	this->mg   = mg;
@@ -269,6 +275,7 @@ CaveV7::CaveV7(MapgenV7 *mg, PseudoRandom *ps, bool is_large_cave) {
 	this->ps = ps;
 	this->c_water_source = mg->c_water_source;
 	this->c_lava_source  = mg->c_lava_source;
+	this->np_caveliquids = &nparams_caveliquids;
 
 	dswitchint = ps->range(1, 14);
 	flooded    = ps->range(1, 2) == 2;
@@ -303,7 +310,7 @@ void CaveV7::makeCave(v3s16 nmin, v3s16 nmax, int max_stone_height) {
 	// Allow a bit more
 	//(this should be more than the maximum radius of the tunnel)
 	s16 insure = 10;
-	s16 more = MAP_BLOCKSIZE - max_tunnel_diameter / 2 - insure;
+	s16 more = MYMAX(MAP_BLOCKSIZE - max_tunnel_diameter / 2 - insure, 1);
 	ar += v3s16(1,0,1) * more * 2;
 	of -= v3s16(1,0,1) * more;
 
@@ -462,11 +469,14 @@ void CaveV7::carveRoute(v3f vec, float f, bool randomize_xz, bool is_ravine) {
 	MapNode airnode(CONTENT_AIR);
 	MapNode waternode(c_water_source);
 	MapNode lavanode(c_lava_source);
-	MapNode liquidnode = ps->range(0, 4) ? lavanode : waternode;
 	
 	v3s16 startp(orp.X, orp.Y, orp.Z);
 	startp += of;
 	
+	float nval = NoisePerlin3D(np_caveliquids, startp.X,
+							startp.Y, startp.Z, mg->seed);
+	MapNode liquidnode = nval < 0.40 ? lavanode : waternode;
+	
 	v3f fp = orp + vec * f;
 	fp.X += 0.1 * ps->range(-10, 10);
 	fp.Z += 0.1 * ps->range(-10, 10);
@@ -502,6 +512,13 @@ void CaveV7::carveRoute(v3f vec, float f, bool randomize_xz, bool is_ravine) {
 
 				v3s16 p(cp.X + x0, cp.Y + y0, cp.Z + z0);
 				p += of;
+				
+				if (!is_ravine && mg->heightmap) {
+					int maplen = node_max.X - node_min.X + 1;
+					int idx = (p.Z - node_min.Z) * maplen + (p.X - node_min.X);
+					if (p.Y >= mg->heightmap[idx])
+						continue;
+				}
 
 				if (vm->m_area.contains(p) == false)
 					continue;
diff --git a/src/cavegen.h b/src/cavegen.h
index 7822816d6..a908c61d8 100644
--- a/src/cavegen.h
+++ b/src/cavegen.h
@@ -75,6 +75,8 @@ public:
 	ManualMapVoxelManipulator *vm;
 	INodeDefManager *ndef;
 
+	NoiseParams *np_caveliquids;
+
 	s16 min_tunnel_diameter;
 	s16 max_tunnel_diameter;
 	u16 tunnel_routepoints;
-- 
2.25.1