Biome API / cavegen: Add definable cave liquid for a biome (#7192)

Add 'node_cave_liquid' as a new field in biome registration.
If field is absent cave liquids fall back to classic behaviour.

doc/lua_api.txt

@@ -5662,6 +5662,10 @@ Definition tables
         node_riverbed = "default:gravel",
         depth_riverbed = 2,
     --  ^ Node placed under river water and thickness of this layer.
+        node_cave_liquid = "default:water_source",
+    --  ^ Nodes placed as a blob of liquid in 50% of large caves.
+    --  ^ If absent, cave liquids fall back to classic behaviour of lava or
+    --  ^ water distributed according to a hardcoded 3D noise.
         y_max = 31000,
         y_min = 1,
     --  ^ Upper and lower limits for biome.

src/mapgen/cavegen.cpp

@@ -279,7 +279,8 @@ CavesRandomWalk::CavesRandomWalk(
 	int water_level,
 	content_t water_source,
 	content_t lava_source,
-	int lava_depth)
+	int lava_depth,
+	BiomeGen *biomegen)
 {
 	assert(ndef);
 
@@ -289,6 +290,7 @@ CavesRandomWalk::CavesRandomWalk(
 	this->water_level    = water_level;
 	this->np_caveliquids = &nparams_caveliquids;
 	this->lava_depth     = lava_depth;
+	this->bmgn           = biomegen;
 
 	c_water_source = water_source;
 	if (c_water_source == CONTENT_IGNORE)
@@ -495,10 +497,22 @@ void CavesRandomWalk::carveRoute(v3f vec, float f, bool randomize_xz)
 	v3s16 startp(orp.X, orp.Y, orp.Z);
 	startp += of;
 
-	float nval = NoisePerlin3D(np_caveliquids, startp.X,
-		startp.Y, startp.Z, seed);
-	MapNode liquidnode = (nval < 0.40f && node_max.Y < lava_depth) ?
-		lavanode : waternode;
+	// Get biome at 'startp', use 'node_cave_liquid' if stated, otherwise
+	// fallback to classic behaviour.
+	MapNode liquidnode = CONTENT_IGNORE;
+
+	if (bmgn) {
+		Biome *biome = (Biome *)bmgn->calcBiomeAtPoint(startp);
+		if (biome->c_cave_liquid != CONTENT_IGNORE)
+			liquidnode = biome->c_cave_liquid;
+	}
+
+	if (liquidnode == CONTENT_IGNORE) {
+		float nval = NoisePerlin3D(np_caveliquids, startp.X,
+			startp.Y, startp.Z, seed);
+		liquidnode = (nval < 0.40f && node_max.Y < lava_depth) ?
+			lavanode : waternode;
+	}
 
 	v3f fp = orp + vec * f;
 	fp.X += 0.1f * ps->range(-10, 10);

src/mapgen/cavegen.h

@@ -114,6 +114,7 @@ class CavesRandomWalk
 	const NodeDefManager *ndef;
 	GenerateNotifier *gennotify;
 	s16 *heightmap;
+	BiomeGen *bmgn;
 
 	// configurable parameters
 	s32 seed;
@@ -153,10 +154,11 @@ class CavesRandomWalk
 
 	// ndef is a mandatory parameter.
 	// If gennotify is NULL, generation events are not logged.
+	// If biomegen is NULL, cave liquids have classic behaviour.
 	CavesRandomWalk(const NodeDefManager *ndef, GenerateNotifier *gennotify =
 		NULL, s32 seed = 0, int water_level = 1, content_t water_source =
 		CONTENT_IGNORE, content_t lava_source = CONTENT_IGNORE,
-		int lava_depth = -256);
+		int lava_depth = -256, BiomeGen *biomegen = NULL);
 
 	// vm and ps are mandatory parameters.
 	// If heightmap is NULL, the surface level at all points is assumed to

src/mapgen/mapgen.cpp

@@ -858,9 +858,10 @@ void MapgenBasic::generateCaves(s16 max_stone_y, s16 large_cave_depth)
 	u32 bruises_count = ps.range(0, 2);
 	for (u32 i = 0; i < bruises_count; i++) {
 		CavesRandomWalk cave(ndef, &gennotify, seed, water_level,
-			c_water_source, CONTENT_IGNORE, lava_depth);
+			c_water_source, c_lava_source, lava_depth, biomegen);
 
-		cave.makeCave(vm, node_min, node_max, &ps, true, max_stone_y, heightmap);
+		cave.makeCave(vm, node_min, node_max, &ps, true, max_stone_y,
+			heightmap);
 	}
 }
 

src/mapgen/mapgen_valleys.cpp

@@ -744,9 +744,10 @@ void MapgenValleys::generateCaves(s16 max_stone_y, s16 large_cave_depth)
 		u32 bruises_count = ps.range(0, 2);
 		for (u32 i = 0; i < bruises_count; i++) {
 			CavesRandomWalk cave(ndef, &gennotify, seed, water_level,
-				c_water_source, c_lava_source, lava_max_height);
+				c_water_source, c_lava_source, lava_max_height, biomegen);
 
-			cave.makeCave(vm, node_min, node_max, &ps, true, max_stone_y, heightmap);
+			cave.makeCave(vm, node_min, node_max, &ps, true, max_stone_y,
+				heightmap);
 		}
 	}
 }

src/mapgen/mg_biome.cpp

@@ -62,6 +62,7 @@ BiomeManager::BiomeManager(Server *server) :
 	b->m_nodenames.emplace_back("mapgen_river_water_source");
 	b->m_nodenames.emplace_back("mapgen_stone");
 	b->m_nodenames.emplace_back("ignore");
+	b->m_nodenames.emplace_back("ignore");
 	m_ndef->pendNodeResolve(b);
 
 	add(b);
@@ -321,4 +322,5 @@ void Biome::resolveNodeNames()
 	getIdFromNrBacklog(&c_river_water, "mapgen_river_water_source", CONTENT_AIR);
 	getIdFromNrBacklog(&c_riverbed,    "mapgen_stone",              CONTENT_AIR);
 	getIdFromNrBacklog(&c_dust,        "ignore",                    CONTENT_IGNORE);
+	getIdFromNrBacklog(&c_cave_liquid, "ignore",                    CONTENT_IGNORE);
 }

src/mapgen/mg_biome.h

@@ -52,6 +52,7 @@ class Biome : public ObjDef, public NodeResolver {
 	content_t c_river_water;
 	content_t c_riverbed;
 	content_t c_dust;
+	content_t c_cave_liquid;
 
 	s16 depth_top;
 	s16 depth_filler;

src/script/lua_api/l_mapgen.cpp

@@ -389,9 +389,11 @@ Biome *read_biome_def(lua_State *L, int index, const NodeDefManager *ndef)
 	b->vertical_blend  = getintfield_default(L,    index, "vertical_blend",  0);
 	b->flags           = 0; // reserved
 
-	b->min_pos = getv3s16field_default(L, index, "min_pos", v3s16(-31000, -31000, -31000));
+	b->min_pos = getv3s16field_default(
+		L, index, "min_pos", v3s16(-31000, -31000, -31000));
 	getintfield(L, index, "y_min", b->min_pos.Y);
-	b->max_pos = getv3s16field_default(L, index, "max_pos", v3s16(31000, 31000, 31000));
+	b->max_pos = getv3s16field_default(
+		L, index, "max_pos", v3s16(31000, 31000, 31000));
 	getintfield(L, index, "y_max", b->max_pos.Y);
 
 	std::vector<std::string> &nn = b->m_nodenames;
@@ -403,6 +405,7 @@ Biome *read_biome_def(lua_State *L, int index, const NodeDefManager *ndef)
 	nn.push_back(getstringfield_default(L, index, "node_river_water", ""));
 	nn.push_back(getstringfield_default(L, index, "node_riverbed",    ""));
 	nn.push_back(getstringfield_default(L, index, "node_dust",        ""));
+	nn.push_back(getstringfield_default(L, index, "node_cave_liquid", ""));
 	ndef->pendNodeResolve(b);
 
 	return b;