diff --git a/src/g_shared/a_dynlight.cpp b/src/g_shared/a_dynlight.cpp
index 4d26df186..95e87baf4 100644
--- a/src/g_shared/a_dynlight.cpp
+++ b/src/g_shared/a_dynlight.cpp
@@ -568,6 +568,7 @@ void ADynamicLight::CollectWithinRadius(const DVector3 &opos, subsector_t *subSe
 	collected_ss.Push({ subSec, opos });
 	subSec->validcount = ::validcount;
 
+	bool hitonesidedback = false;
 	for (unsigned i = 0; i < collected_ss.Size(); i++)
 	{
 		subSec = collected_ss[i].sub;
@@ -596,6 +597,10 @@ void ADynamicLight::CollectWithinRadius(const DVector3 &opos, subsector_t *subSe
 						seg->linedef->validcount = validcount;
 						touching_sides = AddLightNode(&seg->sidedef->lighthead, seg->sidedef, this, touching_sides);
 					}
+					else if (seg->linedef->sidedef[0] == seg->sidedef && seg->linedef->sidedef[1] == nullptr)
+					{
+						hitonesidedback = true;
+					}
 				}
 				if (seg->linedef)
 				{
@@ -657,6 +662,7 @@ void ADynamicLight::CollectWithinRadius(const DVector3 &opos, subsector_t *subSe
 			}
 		}
 	}
+	shadowmapped = hitonesidedback && !(flags4 & MF4_NOSHADOWMAP);
 }
 
 //==========================================================================
@@ -758,6 +764,7 @@ void ADynamicLight::UnlinkLight ()
 	while (touching_sides) touching_sides = DeleteLightNode(touching_sides);
 	while (touching_subsectors) touching_subsectors = DeleteLightNode(touching_subsectors);
 	while (touching_sector) touching_sector = DeleteLightNode(touching_sector);
+	shadowmapped = false;
 }
 
 void ADynamicLight::OnDestroy()
@@ -771,7 +778,7 @@ CCMD(listlights)
 {
 	int walls, sectors, subsecs;
 	int allwalls=0, allsectors=0, allsubsecs = 0;
-	int i=0;
+	int i=0, shadowcount = 0;
 	ADynamicLight * dl;
 	TThinkerIterator<ADynamicLight> it;
 
@@ -780,11 +787,12 @@ CCMD(listlights)
 		walls=0;
 		sectors=0;
 		subsecs = 0;
-		Printf("%s at (%f, %f, %f), color = 0x%02x%02x%02x, radius = %f %s",
+		Printf("%s at (%f, %f, %f), color = 0x%02x%02x%02x, radius = %f %s %s",
 			dl->target? dl->target->GetClass()->TypeName.GetChars() : dl->GetClass()->TypeName.GetChars(),
 			dl->X(), dl->Y(), dl->Z(), dl->args[LIGHT_RED], 
-			dl->args[LIGHT_GREEN], dl->args[LIGHT_BLUE], dl->radius, (dl->flags4 & MF4_ATTENUATE)? "attenuated" : "");
+			dl->args[LIGHT_GREEN], dl->args[LIGHT_BLUE], dl->radius, (dl->flags4 & MF4_ATTENUATE)? "attenuated" : "", dl->shadowmapped? "shadowmapped" : "");
 		i++;
+		shadowcount += dl->shadowmapped;
 
 		if (dl->target)
 		{
@@ -824,7 +832,7 @@ CCMD(listlights)
 		Printf("- %d walls, %d subsectors, %d sectors\n", walls, subsecs, sectors);
 
 	}
-	Printf("%i dynamic lights, %d walls, %d subsectors, %d sectors\n\n\n", i, allwalls, allsubsecs, allsectors);
+	Printf("%i dynamic lights, %d shadowmapped, %d walls, %d subsectors, %d sectors\n\n\n", i, shadowcount, allwalls, allsubsecs, allsectors);
 }
 
 CCMD(listsublights)
diff --git a/src/g_shared/a_dynlight.h b/src/g_shared/a_dynlight.h
index 3e8de3ed8..1a1862957 100644
--- a/src/g_shared/a_dynlight.h
+++ b/src/g_shared/a_dynlight.h
@@ -21,11 +21,12 @@ enum
    LIGHT_SCALE = 3,
 };
 
-// This is as good as something new - and it can be set directly in the ActorInfo!
+// This is as good as something new
 #define MF4_SUBTRACTIVE MF4_MISSILEEVENMORE
 #define MF4_ADDITIVE MF4_MISSILEMORE
 #define MF4_DONTLIGHTSELF MF4_SEESDAGGERS
 #define MF4_ATTENUATE MF4_INCOMBAT
+#define MF4_NOSHADOWMAP MF4_STANDSTILL
 
 enum ELightType
 {
@@ -117,6 +118,7 @@ public:
 	uint8_t color2[3];
 	bool visibletoplayer;
 	bool swapped;
+	bool shadowmapped;
 	int bufferindex;
 
 
diff --git a/src/gl/dynlights/gl_shadowmap.cpp b/src/gl/dynlights/gl_shadowmap.cpp
index 80fc90113..0e997bb0e 100644
--- a/src/gl/dynlights/gl_shadowmap.cpp
+++ b/src/gl/dynlights/gl_shadowmap.cpp
@@ -116,35 +116,43 @@ bool FShadowMap::IsEnabled() const
 int FShadowMap::ShadowMapIndex(ADynamicLight *light)
 {
 	if (IsEnabled())
-		return mLightToShadowmap[light];
-	else
-		return 1024;
+	{
+		auto val = mLightToShadowmap.CheckKey(light);
+		if (val != nullptr) return *val;
+	}
+	return 1024;
 }
 
 void FShadowMap::UploadLights()
 {
-	mLights.Clear();
+	if (mLights.Size() != 1024 * 4) mLights.Resize(1024 * 4);
+	int lightindex = 0;
 	mLightToShadowmap.Clear(mLightToShadowmap.CountUsed() * 2); // To do: allow clearing a TMap while building up a reserve
 
+	// Todo: this should go through the blockmap in a spiral pattern around the player so that closer lights are preferred.
 	TThinkerIterator<ADynamicLight> it(STAT_DLIGHT);
-	while (true)
+	while (auto light = it.Next())
 	{
-		ADynamicLight *light = it.Next();
-		if (!light) break;
+		if (light->shadowmapped)
+		{
+			mLightToShadowmap[light] = lightindex >> 2;
 
-		mLightToShadowmap[light] = mLights.Size() / 4;
+			mLights[lightindex] = light->X();
+			mLights[lightindex+1] = light->Y();
+			mLights[lightindex+2] = light->Z();
+			mLights[lightindex+3] = light->GetRadius();
+			lightindex += 4;
 
-		mLights.Push(light->X());
-		mLights.Push(light->Y());
-		mLights.Push(light->Z());
-		mLights.Push(light->GetRadius());
+			if (lightindex == 1024*4) // Only 1024 lights for now
+				break;
+		}
 
-		if (mLights.Size() == 1024) // Only 1024 lights for now
-			break;
 	}
 
-	while (mLights.Size() < 1024 * 4)
-		mLights.Push(0.0f);
+	for (; lightindex < 1024 * 4; lightindex++)
+	{
+		mLights[lightindex] = 0;
+	}
 
 	if (mLightList == 0)
 		glGenBuffers(1, (GLuint*)&mLightList);
diff --git a/src/scripting/thingdef_data.cpp b/src/scripting/thingdef_data.cpp
index 4bf8db837..32363abdc 100644
--- a/src/scripting/thingdef_data.cpp
+++ b/src/scripting/thingdef_data.cpp
@@ -60,6 +60,7 @@
 #include "r_data/sprites.h"
 #include "serializer.h"
 #include "wi_stuff.h"
+#include "a_dynlight.h"
 
 static TArray<FPropertyInfo*> properties;
 static TArray<AFuncDesc> AFTable;
@@ -479,6 +480,16 @@ static FFlagDef PlayerPawnFlagDefs[] =
 	DEFINE_FLAG(PPF, CROUCHABLEMORPH, APlayerPawn, PlayerFlags),
 };
 
+static FFlagDef DynLightFlagDefs[] =
+{
+	// PlayerPawn flags
+	DEFINE_FLAG(MF4, SUBTRACTIVE, ADynamicLight, flags4),
+	DEFINE_FLAG(MF4, ADDITIVE, ADynamicLight, flags4),
+	DEFINE_FLAG(MF4, DONTLIGHTSELF, ADynamicLight, flags4),
+	DEFINE_FLAG(MF4, ATTENUATE, ADynamicLight, flags4),
+	DEFINE_FLAG(MF4, NOSHADOWMAP, ADynamicLight, flags4),
+};
+
 static FFlagDef PowerSpeedFlagDefs[] =
 {
 	// PowerSpeed flags