Stratum ore: Allow use with no noise for simple horizontal strata

If either of the 2 noise parameters are omitted the ore will occur from y_min
to y_max in a simple horizontal stratum. As this does not compute noise
performance improves, and is ideal for placing many layers.

Clean up some nearby ore documentation.

3 files changed, 25 insertions, 13 deletions

diff --git a/src/mg_ore.cpp b/src/mg_ore.cpp
index 4f4c9c711..979135ed4 100644
--- a/src/mg_ore.cpp
+++ b/src/mg_ore.cpp
@@ -433,14 +433,16 @@ void OreStratum::generate(MMVManip *vm, int mapseed, u32 blockseed,
 	PcgRandom pr(blockseed + 4234);
 	MapNode n_ore(c_ore, 0, ore_param2);
 
-	if (!noise) {
-		int sx = nmax.X - nmin.X + 1;
-		int sz = nmax.Z - nmin.Z + 1;
-		noise = new Noise(&np, 0, sx, sz);
-		noise_stratum_thickness = new Noise(&np_stratum_thickness, 0, sx, sz);
+	if (flags & OREFLAG_USE_NOISE) {
+		if (!(noise && noise_stratum_thickness)) {
+			int sx = nmax.X - nmin.X + 1;
+			int sz = nmax.Z - nmin.Z + 1;
+			noise = new Noise(&np, 0, sx, sz);
+			noise_stratum_thickness = new Noise(&np_stratum_thickness, 0, sx, sz);
+		}
+		noise->perlinMap2D(nmin.X, nmin.Z);
+		noise_stratum_thickness->perlinMap2D(nmin.X, nmin.Z);
 	}
-	noise->perlinMap2D(nmin.X, nmin.Z);
-	noise_stratum_thickness->perlinMap2D(nmin.X, nmin.Z);
 
 	size_t index = 0;
 
@@ -452,10 +454,18 @@ void OreStratum::generate(MMVManip *vm, int mapseed, u32 blockseed,
 				continue;
 		}
 
-		float nmid = noise->result[index];
-		float nhalfthick = noise_stratum_thickness->result[index] / 2.0f;
-		int y0 = MYMAX(nmin.Y, nmid - nhalfthick);
-		int y1 = MYMIN(nmax.Y, nmid + nhalfthick);
+		int y0;
+		int y1;
+
+		if (flags & OREFLAG_USE_NOISE) {
+			float nmid = noise->result[index];
+			float nhalfthick = noise_stratum_thickness->result[index] / 2.0f;
+			y0 = MYMAX(nmin.Y, nmid - nhalfthick);
+			y1 = MYMIN(nmax.Y, nmid + nhalfthick);
+		} else {
+			y0 = nmin.Y;
+			y1 = nmax.Y;
+		}
 
 		for (int y = y0; y <= y1; y++) {
 			if (pr.range(1, clust_scarcity) != 1)
diff --git a/src/mg_ore.h b/src/mg_ore.h
index 4801b152e..e715f348b 100644
--- a/src/mg_ore.h
+++ b/src/mg_ore.h
@@ -135,7 +135,7 @@ public:
 
 class OreStratum : public Ore {
 public:
-	static const bool NEEDS_NOISE = true;
+	static const bool NEEDS_NOISE = false;
 
 	NoiseParams np_stratum_thickness;
 	Noise *noise_stratum_thickness = nullptr;
diff --git a/src/script/lua_api/l_mapgen.cpp b/src/script/lua_api/l_mapgen.cpp
index 7757ea80c..b179ac407 100644
--- a/src/script/lua_api/l_mapgen.cpp
+++ b/src/script/lua_api/l_mapgen.cpp
@@ -1156,7 +1156,9 @@ int ModApiMapgen::l_register_ore(lua_State *L)
 			OreStratum *orestratum = (OreStratum *)ore;
 
 			lua_getfield(L, index, "np_stratum_thickness");
-			read_noiseparams(L, -1, &orestratum->np_stratum_thickness);
+			// If thickness noise missing unset 'use noise' flag
+			if (!read_noiseparams(L, -1, &orestratum->np_stratum_thickness))
+				ore->flags &= ~OREFLAG_USE_NOISE;
 			lua_pop(L, 1);
 
 			break;