- make RR's ingame thunder effect not depend on having seen one specific texture.

This really should check if the player has seen one sector where the effect is active.

source/core/maptypes.h

@@ -100,6 +100,7 @@ enum ESectorExBits
 	SECTOREX_CLOUDSCROLL			= 1,
 	SECTOREX_DRAGGED				= 2,
 	SECTOREX_DONTCLIP				= 4,
+	SECTOREX_SEEN					= 8,
 };
 
 // Flags for retriangulation

source/core/rendering/scene/hw_flats.cpp

@@ -319,6 +319,7 @@ void HWFlat::ProcessSector(HWDrawInfo *di, sectortype * frontsector, int section
 	PlanesAtPoint(frontsector, vp.Pos.X, -vp.Pos.Y, &ceilz, &florz);
 
 	visibility = sectorVisibility(frontsector);
+	frontsector->exflags |= SECTOREX_SEEN;
 	sec = frontsector;
 	section = section_;
 	Sprite = nullptr;

source/games/duke/src/actors_lava.cpp

@@ -479,8 +479,18 @@ void thunder(void)
 	}
 	if (!winderflash && isRR())
 	{
-		auto tex = tileGetTexture(RTILE_CURTAINS);	// this cannot be easily generalized. :(
-		if (tex->isSeen(true))
+		bool seen = false;
+		for (i = 0; i < lightnincnt; i++)
+		{
+			auto sectp = lightninsector[i];
+			if (sectp->exflags & SECTOREX_SEEN)
+			{
+				seen = true;
+				sectp->exflags &= ~SECTOREX_SEEN;
+			}
+		}
+
+		if (seen)
 		{
 			if (krand() > 65000)
 			{