limit light alpha mult to renderflag

src/playsim/actor.h

@@ -508,6 +508,7 @@ enum ActorRenderFlag2
 	RF2_ISOMETRICSPRITES		= 0x0080,
 	RF2_SQUAREPIXELS			= 0x0100,	// apply +ROLLSPRITE scaling math so that non rolling sprites get the same scaling
 	RF2_STRETCHPIXELS			= 0x0200,	// don't apply SQUAREPIXELS for ROLLSPRITES
+	RF2_LIGHTMULTALPHA			= 0x0400,	// attached lights use alpha as intensity multiplier
 };
 
 // This translucency value produces the closest match to Heretic's TINTTAB.

src/rendering/hwrenderer/hw_dynlightdata.cpp

@@ -92,7 +92,7 @@ void AddLightToList(FDynLightData &dld, int group, FDynamicLight * light, bool f
 		cs = 1.0f;
 	}
 
-	if (light->target)
+	if (light->target && (light->target->renderflags2 & RF2_LIGHTMULTALPHA))
 		cs *= (float)light->target->Alpha;
 
 	float r = light->GetRed() / 255.0f * cs;

src/rendering/hwrenderer/scene/hw_spritelight.cpp

@@ -186,7 +186,7 @@ void HWDrawInfo::GetDynSpriteLight(AActor *self, float x, float y, float z, FSec
 						lg = light->GetGreen() / 255.0f;
 						lb = light->GetBlue() / 255.0f;
 
-						if (light->target)
+						if (light->target && (light->target->renderflags2 & RF2_LIGHTMULTALPHA))
 						{
 							float alpha = (float)light->target->Alpha;
 							lr *= alpha;

src/scripting/thingdef_data.cpp

@@ -390,6 +390,7 @@ static FFlagDef ActorFlagDefs[]=
 	DEFINE_FLAG(RF2, ISOMETRICSPRITES, AActor, renderflags2),
 	DEFINE_FLAG(RF2, SQUAREPIXELS, AActor, renderflags2),
 	DEFINE_FLAG(RF2, STRETCHPIXELS, AActor, renderflags2),
+	DEFINE_FLAG(RF2, LIGHTMULTALPHA, AActor, renderflags2),
 
 	// Bounce flags
 	DEFINE_FLAG2(BOUNCE_Walls, BOUNCEONWALLS, AActor, BounceFlags),

wadsrc/static/zscript/actors/shared/dynlights.zs

@@ -73,6 +73,7 @@ class DynamicLight : Actor
 		+FIXMAPTHINGPOS
 		+INVISIBLE
 		+NOTONAUTOMAP
+		+LIGHTMULTALPHA
 	}
 	
 	//==========================================================================