From b14aa305ce11ece147620b250b046e2839cf045f Mon Sep 17 00:00:00 2001
From: DS <vorunbekannt75@web.de>
Date: Fri, 23 Aug 2019 22:16:50 +0200
Subject: [PATCH] Make Mapgen::spreadLight use a queue (#8838)

---
 src/mapgen/mapgen.cpp | 41 +++++++++++++++++++++++------------------
 src/mapgen/mapgen.h   |  5 +++--
 2 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/src/mapgen/mapgen.cpp b/src/mapgen/mapgen.cpp
index 29131d56e..9f17af866 100644
--- a/src/mapgen/mapgen.cpp
+++ b/src/mapgen/mapgen.cpp
@@ -39,6 +39,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "serialization.h"
 #include "util/serialize.h"
 #include "util/numeric.h"
+#include "util/directiontables.h"
 #include "filesys.h"
 #include "log.h"
 #include "mapgen_carpathian.h"
@@ -435,7 +436,8 @@ void Mapgen::setLighting(u8 light, v3s16 nmin, v3s16 nmax)
 }
 
 
-void Mapgen::lightSpread(VoxelArea &a, v3s16 p, u8 light)
+void Mapgen::lightSpread(VoxelArea &a, std::queue<std::pair<v3s16, u8>> &queue,
+	const v3s16 &p, u8 light)
 {
 	if (light <= 1 || !a.contains(p))
 		return;
@@ -455,8 +457,8 @@ void Mapgen::lightSpread(VoxelArea &a, v3s16 p, u8 light)
 	// Bail out only if we have no more light from either bank to propogate, or
 	// we hit a solid block that light cannot pass through.
 	if ((light_day  <= (n.param1 & 0x0F) &&
-		light_night <= (n.param1 & 0xF0)) ||
-		!ndef->get(n).light_propagates)
+			light_night <= (n.param1 & 0xF0)) ||
+			!ndef->get(n).light_propagates)
 		return;
 
 	// Since this recursive function only terminates when there is no light from
@@ -467,12 +469,8 @@ void Mapgen::lightSpread(VoxelArea &a, v3s16 p, u8 light)
 
 	n.param1 = light;
 
-	lightSpread(a, p + v3s16(0, 0, 1), light);
-	lightSpread(a, p + v3s16(0, 1, 0), light);
-	lightSpread(a, p + v3s16(1, 0, 0), light);
-	lightSpread(a, p - v3s16(0, 0, 1), light);
-	lightSpread(a, p - v3s16(0, 1, 0), light);
-	lightSpread(a, p - v3s16(1, 0, 0), light);
+	// add to queue
+	queue.emplace(p, light);
 }
 
 
@@ -525,9 +523,10 @@ void Mapgen::propagateSunlight(v3s16 nmin, v3s16 nmax, bool propagate_shadow)
 }
 
 
-void Mapgen::spreadLight(v3s16 nmin, v3s16 nmax)
+void Mapgen::spreadLight(const v3s16 &nmin, const v3s16 &nmax)
 {
 	//TimeTaker t("spreadLight");
+	std::queue<std::pair<v3s16, u8>> queue;
 	VoxelArea a(nmin, nmax);
 
 	for (int z = a.MinEdge.Z; z <= a.MaxEdge.Z; z++) {
@@ -551,18 +550,24 @@ void Mapgen::spreadLight(v3s16 nmin, v3s16 nmax)
 
 				u8 light = n.param1;
 				if (light) {
-					lightSpread(a, v3s16(x,     y,     z + 1), light);
-					lightSpread(a, v3s16(x,     y + 1, z    ), light);
-					lightSpread(a, v3s16(x + 1, y,     z    ), light);
-					lightSpread(a, v3s16(x,     y,     z - 1), light);
-					lightSpread(a, v3s16(x,     y - 1, z    ), light);
-					lightSpread(a, v3s16(x - 1, y,     z    ), light);
+					const v3s16 p(x, y, z);
+					// spread to all 6 neighbor nodes
+					for (const auto &dir : g_6dirs)
+						lightSpread(a, queue, p + dir, light);
 				}
 			}
 		}
 	}
 
-	//printf("spreadLight: %dms\n", t.stop());
+	while (!queue.empty()) {
+		const auto &i = queue.front();
+		// spread to all 6 neighbor nodes
+		for (const auto &dir : g_6dirs)
+			lightSpread(a, queue, i.first + dir, i.second);
+		queue.pop();
+	}
+
+	//printf("spreadLight: %lums\n", t.stop());
 }
 
 
@@ -877,7 +882,7 @@ void MapgenBasic::generateDungeons(s16 max_stone_y)
 		return;
 
 	PseudoRandom ps(blockseed + 70033);
-	
+
 	DungeonParams dp;
 
 	dp.np_alt_wall =
diff --git a/src/mapgen/mapgen.h b/src/mapgen/mapgen.h
index b10aa7b9e..0ac26d538 100644
--- a/src/mapgen/mapgen.h
+++ b/src/mapgen/mapgen.h
@@ -190,11 +190,12 @@ public:
 	void updateLiquid(UniqueQueue<v3s16> *trans_liquid, v3s16 nmin, v3s16 nmax);
 
 	void setLighting(u8 light, v3s16 nmin, v3s16 nmax);
-	void lightSpread(VoxelArea &a, v3s16 p, u8 light);
+	void lightSpread(VoxelArea &a, std::queue<std::pair<v3s16, u8>> &queue,
+		const v3s16 &p, u8 light);
 	void calcLighting(v3s16 nmin, v3s16 nmax, v3s16 full_nmin, v3s16 full_nmax,
 		bool propagate_shadow = true);
 	void propagateSunlight(v3s16 nmin, v3s16 nmax, bool propagate_shadow);
-	void spreadLight(v3s16 nmin, v3s16 nmax);
+	void spreadLight(const v3s16 &nmin, const v3s16 &nmax);
 
 	virtual void makeChunk(BlockMakeData *data) {}
 	virtual int getGroundLevelAtPoint(v2s16 p) { return 0; }