From 773aa8c57b70dd85273cb61286f8be577b4ca3aa Mon Sep 17 00:00:00 2001
From: paramat <mat.gregory@virginmedia.com>
Date: Sun, 1 Mar 2015 01:30:47 +0000
Subject: [PATCH] Mgv6: Add heightmap. Do not make large caves that are
 entirely above ground

---
 src/cavegen.cpp   | 30 ++++++++++++++++++++++++++++++
 src/mapgen_v6.cpp |  5 +++++
 2 files changed, 35 insertions(+)

diff --git a/src/cavegen.cpp b/src/cavegen.cpp
index 6010780e9..bac656511 100644
--- a/src/cavegen.cpp
+++ b/src/cavegen.cpp
@@ -173,6 +173,36 @@ void CaveV6::makeTunnel(bool dirswitch) {
 		);
 	}
 
+	// Do not make large caves that are entirely above ground.
+	// It is only necessary to check the startpoint and endpoint.
+	if (large_cave) {
+		v3s16 orpi(orp.X, orp.Y, orp.Z);
+		v3s16 veci(vec.X, vec.Y, vec.Z);
+		s16 h1;
+		s16 h2;
+
+		v3s16 p1 = orpi + veci + of + rs / 2;
+		if (p1.Z >= node_min.Z && p1.Z <= node_max.Z &&
+				p1.X >= node_min.X && p1.X <= node_max.X) {
+			u32 index1 = (p1.Z - node_min.Z) * mg->ystride + (p1.X - node_min.X);
+			h1 = mg->heightmap[index1];
+		} else {
+			h1 = water_level; // If not in heightmap
+		}
+
+		v3s16 p2 = orpi + of + rs / 2;
+		if (p2.Z >= node_min.Z && p2.Z <= node_max.Z &&
+				p2.X >= node_min.X && p2.X <= node_max.X) {
+			u32 index2 = (p2.Z - node_min.Z) * mg->ystride + (p2.X - node_min.X);
+			h2 = mg->heightmap[index2];
+		} else {
+			h2 = water_level;
+		}
+
+		if (p1.Y > h1 && p2.Y > h2) // If startpoint and endpoint are above ground
+			return;
+	}
+
 	vec += main_direction;
 
 	v3f rp = orp + vec;
diff --git a/src/mapgen_v6.cpp b/src/mapgen_v6.cpp
index 95cdbd279..4783e4285 100644
--- a/src/mapgen_v6.cpp
+++ b/src/mapgen_v6.cpp
@@ -55,6 +55,8 @@ MapgenV6::MapgenV6(int mapgenid, MapgenParams *params, EmergeManager *emerge)
 	this->m_emerge = emerge;
 	this->ystride = csize.X; //////fix this
 
+	this->heightmap = new s16[csize.X * csize.Z];
+
 	MapgenV6Params *sp = (MapgenV6Params *)params->sparams;
 	this->spflags     = sp->spflags;
 	this->freq_desert = sp->freq_desert;
@@ -498,6 +500,9 @@ void MapgenV6::makeChunk(BlockMakeData *data)
 
 	}
 
+	// Create heightmap after mudflow
+	updateHeightmap(node_min, node_max);
+
 	// Add dungeons
 	if ((flags & MG_DUNGEONS) && (stone_surface_max_y >= node_min.Y)) {
 		DungeonParams dp;
-- 
2.25.1