diff --git a/src/map.cpp b/src/map.cpp
index dce3bdc09..1ab2b32ae 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -690,9 +690,11 @@ void Map::updateLighting(enum LightBank bank,
 	core::map<v3s16, bool> light_sources;
 
 	core::map<v3s16, u8> unlight_from;
+
+	int num_bottom_invalid = 0;
 	
 	{
-	//TimeTaker t("first stuff");
+	TimeTaker t("first stuff");
 
 	core::map<v3s16, MapBlock*>::Iterator i;
 	i = a_blocks.getIterator();
@@ -758,6 +760,9 @@ void Map::updateLighting(enum LightBank bank,
 			{
 				bool bottom_valid = block->propagateSunlight(light_sources);
 
+				if(!bottom_valid)
+					num_bottom_invalid++;
+
 				// If bottom is valid, we're done.
 				if(bottom_valid)
 					break;
@@ -792,6 +797,8 @@ void Map::updateLighting(enum LightBank bank,
 	}
 
 	}
+
+	infostream<<"num_bottom_invalid="<<num_bottom_invalid<<std::endl;
 	
 	/*
 		Enable this to disable proper lighting for speeding up map
@@ -885,15 +892,15 @@ void Map::updateLighting(enum LightBank bank,
 		}
 
 		{
-			TimeTaker timer("unSpreadLight");
+			//TimeTaker timer("unSpreadLight");
 			vmanip.unspreadLight(bank, unlight_from, light_sources, nodemgr);
 		}
 		{
-			TimeTaker timer("spreadLight");
+			//TimeTaker timer("spreadLight");
 			vmanip.spreadLight(bank, light_sources, nodemgr);
 		}
 		{
-			TimeTaker timer("blitBack");
+			//TimeTaker timer("blitBack");
 			vmanip.blitBack(modified_blocks);
 		}
 		/*infostream<<"emerge_time="<<emerge_time<<std::endl;
diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index 6fecbb450..25fa427aa 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -26,6 +26,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "content_sao.h"
 #include "nodedef.h"
 #include "content_mapnode.h" // For content_mapnode_get_new_name
+#include "voxelalgorithms.h"
 
 namespace mapgen
 {
@@ -2335,6 +2336,10 @@ void make_block(BlockMakeData *data)
 		}
 	}
 
+	/*
+		Calculate lighting
+	*/
+
 }
 
 BlockMakeData::BlockMakeData():
diff --git a/src/test.cpp b/src/test.cpp
index ecced33c3..cb01edffd 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -55,6 +55,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #define CONTENT_STONE 0
 #define CONTENT_GRASS 0x800
+#define CONTENT_TORCH 100
 
 void define_some_nodes(IWritableItemDefManager *idef, IWritableNodeDefManager *ndef)
 {
@@ -105,6 +106,22 @@ void define_some_nodes(IWritableItemDefManager *idef, IWritableNodeDefManager *n
 	f.is_ground_content = true;
 	idef->registerItem(itemdef);
 	ndef->set(i, f);
+
+	/*
+		Torch (minimal definition for lighting tests)
+	*/
+	i = CONTENT_TORCH;
+	itemdef = ItemDefinition();
+	itemdef.type = ITEM_NODE;
+	itemdef.name = "default:torch";
+	f = ContentFeatures();
+	f.name = itemdef.name;
+	f.param_type = CPT_LIGHT;
+	f.light_propagates = true;
+	f.sunlight_propagates = true;
+	f.light_source = LIGHT_MAX-1;
+	idef->registerItem(itemdef);
+	ndef->set(i, f);
 }
 
 struct TestUtilities
@@ -488,6 +505,9 @@ struct TestVoxelAlgorithms
 {
 	void Run(INodeDefManager *ndef)
 	{
+		/*
+			voxalgo::propagateSunlight
+		*/
 		{
 			VoxelManipulator v;
 			for(u16 z=0; z<3; z++)
@@ -593,6 +613,40 @@ struct TestVoxelAlgorithms
 				assert(res.bottom_sunlight_valid == true);
 			}
 		}
+		/*
+			voxalgo::clearLightAndCollectSources
+		*/
+		{
+			VoxelManipulator v;
+			for(u16 z=0; z<3; z++)
+			for(u16 y=0; y<3; y++)
+			for(u16 x=0; x<3; x++)
+			{
+				v3s16 p(x,y,z);
+				v.setNode(p, MapNode(CONTENT_AIR));
+			}
+			VoxelArea a(v3s16(0,0,0), v3s16(2,2,2));
+			v.setNodeNoRef(v3s16(0,0,0), MapNode(CONTENT_STONE));
+			v.setNodeNoRef(v3s16(1,1,1), MapNode(CONTENT_TORCH));
+			{
+				MapNode n(CONTENT_AIR);
+				n.setLight(LIGHTBANK_DAY, 1, ndef);
+				v.setNode(v3s16(1,1,2), n);
+			}
+			{
+				core::map<v3s16, bool> light_sources;
+				core::map<v3s16, u8> unlight_from;
+				voxalgo::clearLightAndCollectSources(v, a, LIGHTBANK_DAY,
+						ndef, light_sources, unlight_from);
+				//v.print(dstream, ndef, VOXELPRINT_LIGHT_DAY);
+				assert(v.getNode(v3s16(0,1,1)).getLight(LIGHTBANK_DAY, ndef)
+						== 0);
+				assert(light_sources.find(v3s16(1,1,1)) != NULL);
+				assert(light_sources.size() == 1);
+				assert(unlight_from.find(v3s16(1,1,2)) != NULL);
+				assert(unlight_from.size() == 1);
+			}
+		}
 	}
 };
 
diff --git a/src/voxelalgorithms.cpp b/src/voxelalgorithms.cpp
index ae609e96a..ab6cbdfa2 100644
--- a/src/voxelalgorithms.cpp
+++ b/src/voxelalgorithms.cpp
@@ -37,6 +37,42 @@ void setLight(VoxelManipulator &v, VoxelArea a, u8 light,
 	}
 }
 
+void clearLightAndCollectSources(VoxelManipulator &v, VoxelArea a,
+		enum LightBank bank, INodeDefManager *ndef,
+		core::map<v3s16, bool> & light_sources,
+		core::map<v3s16, u8> & unlight_from)
+{
+	// The full area we shall touch
+	VoxelArea required_a = a;
+	required_a.pad(v3s16(0,0,0));
+	// Make sure we have access to it
+	v.emerge(a);
+
+	for(s32 x=a.MinEdge.X; x<=a.MaxEdge.X; x++)
+	for(s32 z=a.MinEdge.Z; z<=a.MaxEdge.Z; z++)
+	for(s32 y=a.MinEdge.Y; y<=a.MaxEdge.Y; y++)
+	{
+		v3s16 p(x,y,z);
+		MapNode &n = v.getNodeRefUnsafe(p);
+		u8 oldlight = n.getLight(bank, ndef);
+		n.setLight(bank, 0, ndef);
+
+		// If node sources light, add to list
+		u8 source = ndef->get(n).light_source;
+		if(source != 0)
+			light_sources[p] = true;
+
+		// Collect borders for unlighting
+		if((x==a.MinEdge.X || x == a.MaxEdge.X
+		|| y==a.MinEdge.Y || y == a.MaxEdge.Y
+		|| z==a.MinEdge.Z || z == a.MaxEdge.Z)
+		&& oldlight != 0)
+		{
+			unlight_from.insert(p, oldlight);
+		}
+	}
+}
+
 SunlightPropagateResult propagateSunlight(VoxelManipulator &v, VoxelArea a,
 		bool inexistent_top_provides_sunlight,
 		core::map<v3s16, bool> & light_sources,
@@ -69,11 +105,6 @@ SunlightPropagateResult propagateSunlight(VoxelManipulator &v, VoxelArea a,
 			overtop_has_sunlight = (v.getNodeRefUnsafe(p_overtop).getLight(
 					LIGHTBANK_DAY, ndef) == LIGHT_SUN);
 
-		dstream<<"inexistent_top_provides_sunlight="
-				<<inexistent_top_provides_sunlight<<std::endl;
-		dstream<<"v.exists(p_overtop)="
-				<<v.exists(p_overtop)<<std::endl;
-
 		// Copy overtop's sunlight all over the place
 		u8 incoming_light = overtop_has_sunlight ? LIGHT_SUN : 0;
 		for(s32 y=max_y; y>=min_y; y--)
diff --git a/src/voxelalgorithms.h b/src/voxelalgorithms.h
index 3dea233dc..9c90e18a9 100644
--- a/src/voxelalgorithms.h
+++ b/src/voxelalgorithms.h
@@ -21,6 +21,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define VOXELALGORITHMS_HEADER
 
 #include "voxel.h"
+#include "mapnode.h"
 
 namespace voxalgo
 {
@@ -30,6 +31,11 @@ namespace voxalgo
 void setLight(VoxelManipulator &v, VoxelArea a, u8 light,
 		INodeDefManager *ndef);
 
+void clearLightAndCollectSources(VoxelManipulator &v, VoxelArea a,
+		enum LightBank bank, INodeDefManager *ndef,
+		core::map<v3s16, bool> & light_sources,
+		core::map<v3s16, u8> & unlight_from);
+
 struct SunlightPropagateResult
 {
 	bool bottom_sunlight_valid;