Add more ways to prevent GZDoom from drawing skybox walls

Add noskywalls flag to sectors and linedefs

specs/udmf_zdoom.txt

@@ -140,6 +140,7 @@ Note: All <bool> fields default to false unless mentioned otherwise.
                                   // 12: Unexplored secret wall.
                                   // 13: Portal line.
       revealed = <bool>;          // true = line is initially visible on automap.
+      noskywalls = <bool>;        // true = skies are not drawn above or below this line
 
       health = <int>;             // Amount of hitpoints for this line.
       healthgroup = <int>;        // ID of destructible object to synchronize hitpoints (optional, default is 0)
@@ -294,6 +295,8 @@ Note: All <bool> fields default to false unless mentioned otherwise.
       colorization_floor = <int>;     // Sets a colorization record for the floor texture. Colorization records must be defined in TEXTURES.
       colorization_ceiling = <int>;     // Sets a colorization record for the ceiling texture. Colorization records must be defined in TEXTURES.
 
+      noskywalls = <bool>;            // If true, do not draw skybox walls above/below this sector
+
       portal_ceil_blocksound = <bool>;     // ceiling portal blocks sound.
       portal_ceil_disabled = <bool>;       // ceiling portal disabled.
       portal_ceil_nopass = <bool>;         // ceiling portal blocks movement if true.

src/doomdata.h

@@ -173,7 +173,7 @@ enum ELineFlags : unsigned
 	ML_BLOCKHITSCAN				= 0x08000000,	// blocks hitscan attacks
 	ML_3DMIDTEX_IMPASS			= 0x10000000,	// [TP] if 3D midtex, behaves like a height-restricted ML_BLOCKING
 	ML_REVEALED					= 0x20000000,	// set if revealed in automap
-
+	ML_NOSKYWALLS				= 0x40000000,	// Don't draw sky above or below walls
 	ML_PORTALCONNECT			= 0x80000000,	// for internal use only: This line connects to a sector with a linked portal (used to speed up sight checks.)
 };
 

src/gamedata/r_defs.h

@@ -485,6 +485,7 @@ enum
 	SECMF_DRAWN				= 128,	// sector has been drawn at least once
 	SECMF_HIDDEN			= 256,	// Do not draw on textured automap
 	SECMF_OVERLAPPING		= 512,	// floor and ceiling overlap and require special renderer action.
+	SECMF_NOSKYWALLS		= 1024,	// Do not draw "sky walls"
 };
 
 enum

src/maploader/udmf.cpp

@@ -1074,6 +1074,10 @@ class UDMFParser : public UDMFParserBase
 				ld->automapstyle = AutomapLineStyle(CheckInt(key));
 				continue;
 
+			case NAME_NoSkyWalls:
+				Flag(ld->flags, ML_NOSKYWALLS, key);
+				continue;
+
 			case NAME_MoreIds:
 				// delay parsing of the tag string until parsing of the sector is complete
 				// This ensures that the ID is always the first tag in the list.
@@ -1662,6 +1666,10 @@ class UDMFParser : public UDMFParserBase
 					sec->AdditiveColors[sector_t::sprites] = CheckInt(key) | 0xff000000;
 					break;
 
+				case NAME_NoSkyWalls:
+					Flag(sec->MoreFlags, SECMF_NOSKYWALLS, key);
+					break;
+
 				case NAME_colorization_floor:
 					sec->SetTextureFx(sector_t::floor, TexMan.GetTextureManipulation(CheckString(key)));
 					break;

src/rendering/hwrenderer/scene/hw_sky.cpp

@@ -230,8 +230,8 @@ void HWWall::SkyTop(HWDrawInfo *di, seg_t * seg,sector_t * fs,sector_t * bs,vert
 {
 	if (fs->GetTexture(sector_t::ceiling)==skyflatnum)
 	{
-		if (bs->special == GLSector_NoSkyDraw) return;
-		if (bs->GetTexture(sector_t::ceiling)==skyflatnum) 
+		if (bs->special == GLSector_NoSkyDraw || bs->MoreFlags & SECMF_NOSKYWALLS || seg->linedef->flags & ML_NOSKYWALLS) return;
+		if (bs->GetTexture(sector_t::ceiling)==skyflatnum)
 		{
 			// if the back sector is closed the sky must be drawn!
 			if (bs->ceilingplane.ZatPoint(v1) > bs->floorplane.ZatPoint(v1) ||
@@ -324,7 +324,7 @@ void HWWall::SkyBottom(HWDrawInfo *di, seg_t * seg,sector_t * fs,sector_t * bs,v
 {
 	if (fs->GetTexture(sector_t::floor)==skyflatnum)
 	{
-		if (bs->special == GLSector_NoSkyDraw) return;
+		if (bs->special == GLSector_NoSkyDraw || bs->MoreFlags & SECMF_NOSKYWALLS || seg->linedef->flags & ML_NOSKYWALLS) return;
 		FTexture * tex = TexMan.GetTexture(seg->sidedef->GetTexture(side_t::bottom), true);
 
 		// For lower skies the normal logic only applies to walls with no lower texture.

src/utility/namedef.h

@@ -594,6 +594,7 @@ xx(ColorAdd_Floor)
 xx(ColorAdd_Ceiling)
 xx(ColorAdd_Sprites)
 xx(ColorAdd_Walls)
+xx(NoSkyWalls)
 xx(Desaturation)
 xx(SoundSequence)
 xx(Silent)