Skymist is a third sky layer with transparency, and adopts the fade color and skyfog density. Size not connected to SKY1 or SKY2. Works with 6-sided skyboxes. Three template pngs (skymist1, 2, & 3) all 1x544 pixels, 8-bit grayscale with transparency are part of gzdoom.pk3 for general usage. Can supply custom lump through mapinfo. Console command 'skymisttoggle' shows the effect (make sure fade has a non-zero color in mapinfo and skyfog has non-zero density). Oh, and skyfog now works with 6-sided skyboxes.

src/common/rendering/hwrenderer/data/hw_skydome.cpp

@@ -488,7 +488,7 @@ void FSkyVertexBuffer::DoRenderDome(FRenderState& state, FGameTexture* tex, int
 		RenderRow(state, DT_TriangleFan, rc, primStart);
 		state.EnableTexture(true);
 	}
-	state.SetObjectColor(0xffffffff);
+	state.SetObjectColor(color);
 	for (int i = 1; i <= mRows; i++)
 	{
 		RenderRow(state, DT_TriangleStrip, i, primStart, i == 1);

src/console/c_cmds.cpp

@@ -942,6 +942,16 @@ CCMD(changesky)
 	InitSkyMap (primaryLevel);
 }
 
+//-----------------------------------------------------------------------------
+//
+//
+//
+//-----------------------------------------------------------------------------
+CCMD(skymisttoggle)
+{
+	primaryLevel->flags3 ^= LEVEL3_SKYMIST;
+}
+
 //-----------------------------------------------------------------------------
 //
 //

src/g_level.cpp

@@ -1835,8 +1835,10 @@ void FLevelLocals::Init()
 
 	skyspeed1 = info->skyspeed1;
 	skyspeed2 = info->skyspeed2;
+	skymistspeed = info->skymistspeed;
 	skytexture1 = TexMan.GetTextureID(info->SkyPic1.GetChars(), ETextureType::Wall, FTextureManager::TEXMAN_Overridable | FTextureManager::TEXMAN_ReturnFirst);
 	skytexture2 = TexMan.GetTextureID(info->SkyPic2.GetChars(), ETextureType::Wall, FTextureManager::TEXMAN_Overridable | FTextureManager::TEXMAN_ReturnFirst);
+	skymisttexture = TexMan.GetTextureID(info->SkyMistPic.GetChars(), ETextureType::Wall, FTextureManager::TEXMAN_Overridable | FTextureManager::TEXMAN_ReturnFirst);
 	fadeto = info->fadeto;
 	cdtrack = info->cdtrack;
 	cdid = info->cdid;

src/g_levellocals.h

@@ -687,12 +687,14 @@ public:
 	unsigned int cdid;
 	FTextureID	skytexture1;
 	FTextureID	skytexture2;
+	FTextureID	skymisttexture;
 
 	float		skyspeed1;				// Scrolling speed of sky textures, in pixels per ms
 	float		skyspeed2;
+	float		skymistspeed;
 
 	double		sky1pos, sky2pos;
-	float		hw_sky1pos, hw_sky2pos;
+	float		hw_sky1pos, hw_sky2pos, hw_skymistpos;
 	bool		skystretch;
 	uint32_t	globalcolormap;
 

src/gamedata/g_mapinfo.cpp

@@ -97,6 +97,7 @@ level_info_t *FindLevelInfo (const char *mapname, bool allowdefault)
 		if (TheDefaultLevelInfo.LevelName.IsEmpty())
 		{
 			TheDefaultLevelInfo.SkyPic2 = TheDefaultLevelInfo.SkyPic1 = "SKY1";
+			TheDefaultLevelInfo.SkyMistPic = "SKYMIST1";
 			TheDefaultLevelInfo.LevelName = "Unnamed";
 		}
 		return &TheDefaultLevelInfo;
@@ -255,6 +256,7 @@ void level_info_t::Reset()
 	NextMap = "";
 	NextSecretMap = "";
 	SkyPic1 = SkyPic2 = "-NOFLAT-";
+	SkyMistPic = "SKYMIST1";
 	cluster = 0;
 	partime = 0;
 	sucktime = 0;
@@ -277,7 +279,7 @@ void level_info_t::Reset()
 	musicorder = 0;
 	Snapshot = { 0,0,0,0,0,nullptr };
 	deferred.Clear();
-	skyspeed1 = skyspeed2 = 0.f;
+	skyspeed1 = skyspeed2 = skymistspeed = 0.f;
 	fadeto = 0;
 	outsidefog = 0xff000000;
 	cdtrack = 0;
@@ -1099,6 +1101,20 @@ DEFINE_MAP_OPTION(sky2, true)
 	}
 }
 
+DEFINE_MAP_OPTION(skymist, true)
+{
+	parse.ParseAssign();
+	parse.ParseLumpOrTextureName(info->SkyMistPic);
+	if (parse.CheckFloat())
+	{
+		if (parse.HexenHack)
+		{
+			parse.sc.Float /= 256;
+		}
+		info->skymistspeed = float(parse.sc.Float * (TICRATE / 1000.));
+	}
+}
+
 // Vavoom compatibility
 DEFINE_MAP_OPTION(skybox, true)
 {
@@ -1857,7 +1873,8 @@ MapFlagHandlers[] =
 	{ "disableskyboxao",				MITYPE_CLRFLAG3,	LEVEL3_SKYBOXAO, 0 },
 	{ "avoidmelee",						MITYPE_SETFLAG3,	LEVEL3_AVOIDMELEE, 0 },
 	{ "attenuatelights",				MITYPE_SETFLAG3,	LEVEL3_ATTENUATE, 0 },
-	{ "nofogofwar",					MITYPE_SETFLAG3,	LEVEL3_NOFOGOFWAR, 0 },
+	{ "nofogofwar",						MITYPE_SETFLAG3,	LEVEL3_NOFOGOFWAR, 0 },
+	{ "useskymist",						MITYPE_SETFLAG3,	LEVEL3_SKYMIST, 0 },
 	{ "nobotnodes",						MITYPE_IGNORE,	0, 0 },		// Skulltag option: nobotnodes
 	{ "nopassover",						MITYPE_COMPATFLAG, COMPATF_NO_PASSMOBJ, 0 },
 	{ "passover",						MITYPE_CLRCOMPATFLAG, COMPATF_NO_PASSMOBJ, 0 },

src/gamedata/g_mapinfo.h

@@ -274,6 +274,7 @@ enum ELevelFlags : unsigned int
 	LEVEL3_LIGHTCREATED			= 0x00080000,	// a light had been created in the last frame
 	LEVEL3_NOFOGOFWAR			= 0x00100000,	// disables effect of r_radarclipper CVAR on this map
 	LEVEL3_SECRET				= 0x00200000,   // level is a secret level
+	LEVEL3_SKYMIST				= 0x00400000,   // level skyfog uses the skymist texture
 };
 
 
@@ -333,6 +334,7 @@ struct level_info_t
 	FString		PName;
 	FString		SkyPic1;
 	FString		SkyPic2;
+	FString		SkyMistPic;
 	FString		FadeTable;
 	FString		CustomColorMap;
 	FString		F1Pic;
@@ -359,6 +361,7 @@ struct level_info_t
 	TArray<acsdefered_t> deferred;
 	float		skyspeed1;
 	float		skyspeed2;
+	float		skymistspeed;
 	uint32_t	fadeto;
 	uint32_t	outsidefog;
 	int			cdtrack;

src/p_saveg.cpp

@@ -964,6 +964,7 @@ void FLevelLocals::Serialize(FSerializer &arc, bool hubload)
 		("fadeto", fadeto)
 		("skyspeed1", skyspeed1)
 		("skyspeed2", skyspeed2)
+		("skymistspeed", skymistspeed)
 		("found_secrets", found_secrets)
 		("found_items", found_items)
 		("killed_monsters", killed_monsters)
@@ -977,6 +978,7 @@ void FLevelLocals::Serialize(FSerializer &arc, bool hubload)
 		("totaltime", i)
 		("skytexture1", skytexture1)
 		("skytexture2", skytexture2)
+		("skymisttexture", skymisttexture)
 		("fogdensity", fogdensity)
 		("outsidefogdensity", outsidefogdensity)
 		("skyfog", skyfog)

src/p_setup.cpp

@@ -212,6 +212,10 @@ static void PrecacheLevel(FLevelLocals *Level)
 	{
 		AddToList(hitlist.Data(), Level->skytexture2, FTextureManager::HIT_Sky);
 	}
+	if (Level->skymisttexture.isValid())
+	{
+		AddToList(hitlist.Data(), Level->skymisttexture, FTextureManager::HIT_Sky);
+	}
 
 	static const BITFIELD checkForTextureFlags = FTextureManager::TEXMAN_Overridable | FTextureManager::TEXMAN_TryAny | FTextureManager::TEXMAN_ReturnFirst | FTextureManager::TEXMAN_DontCreate;
 

src/playsim/p_acs.cpp

@@ -5545,6 +5545,7 @@ int DLevelScript::CallFunction(int argCount, int funcIndex, int32_t *args, int &
 		{
 			if (args[0] == 1) Level->skyspeed1 = ACSToFloat(args[1]);
 			else if (args[0] == 2) Level->skyspeed2 = ACSToFloat(args[1]);
+			else if (args[0] == 3) Level->skymistspeed = ACSToFloat(args[1]);
 			return 1;
 		}
 

src/rendering/hwrenderer/scene/hw_portal.h

@@ -13,9 +13,9 @@ class FSkyBox;
 
 struct HWSkyInfo
 {
-	float x_offset[2];
+	float x_offset[3];
 	float y_offset;		// doubleskies don't have a y-offset
-	FGameTexture * texture[2];
+	FGameTexture * texture[3];
 	FTextureID skytexno1;
 	bool mirrored;
 	bool doublesky;
@@ -351,7 +351,6 @@ public:
 
 };
 
-
 struct HWSkyPortal : public HWPortal
 {
 	HWSkyInfo * origin;

src/rendering/hwrenderer/scene/hw_sky.cpp

@@ -118,6 +118,9 @@ void HWSkyInfo::init(HWDrawInfo *di, sector_t* sec, int skypos, int sky1, PalEnt
 	}
 	else fadecolor = 0;
 
+	texture[2] = TexMan.GetGameTexture(di->Level->skymisttexture);
+	x_offset[2] = di->Level->hw_skymistpos;
+
 }
 
 

src/rendering/hwrenderer/scene/hw_skyportal.cpp

@@ -74,19 +74,26 @@ void HWSkyPortal::DrawContents(HWDrawInfo *di, FRenderState &state)
 			vertexBuffer->RenderDome(state, origin->texture[0], origin->x_offset[0], origin->y_offset, origin->mirrored, FSkyVertexBuffer::SKYMODE_MAINLAYER, !!(di->Level->flags & LEVEL_FORCETILEDSKY));
 			state.SetTextureMode(TM_NORMAL);
 		}
-		
+
 		state.AlphaFunc(Alpha_Greater, 0.f);
 		
 		if (origin->doublesky && origin->texture[1])
 		{
 			vertexBuffer->RenderDome(state, origin->texture[1], origin->x_offset[1], origin->y_offset, false, FSkyVertexBuffer::SKYMODE_SECONDLAYER, !!(di->Level->flags & LEVEL_FORCETILEDSKY));
 		}
+	}
 
-		if (di->Level->skyfog>0 && !di->isFullbrightScene()  && (origin->fadecolor & 0xffffff) != 0)
+	if (di->Level->skyfog>0 && (origin->fadecolor & 0xffffff) != 0)
+	{
+		PalEntry FadeColor = origin->fadecolor;
+		FadeColor.a = clamp<int>(di->Level->skyfog, 0, 255);
+
+		if (di->Level->flags3 & LEVEL3_SKYMIST && origin->texture[2])
+		{
+			vertexBuffer->RenderDome(state, origin->texture[2], origin->x_offset[2], 0.f, false, FSkyVertexBuffer::SKYMODE_FOGLAYER, !!(di->Level->flags & LEVEL_FORCETILEDSKY), 0, 0, FadeColor);
+		}
+		else if (!di->isFullbrightScene())
 		{
-			PalEntry FadeColor = origin->fadecolor;
-			FadeColor.a = clamp<int>(di->Level->skyfog, 0, 255);
-
 			state.EnableTexture(false);
 			state.SetObjectColor(FadeColor);
 			state.Draw(DT_Triangles, 0, 12);

src/rendering/r_sky.cpp

@@ -79,6 +79,10 @@ void InitSkyMap(FLevelLocals *Level)
 	{
 		Level->skytexture1 = TexMan.GetFrontSkyLayer(Level->skytexture1);
 	}
+	if (Level->skymisttexture.isNull())
+	{
+		Level->skymisttexture = TexMan.CheckForTexture("skymist1", ETextureType::Any);
+	}
 
 	skytex1 = TexMan.GetGameTexture(Level->skytexture1, false);
 	skytex2 = TexMan.GetGameTexture(Level->skytexture2, false);
@@ -143,6 +147,7 @@ void R_UpdateSky (uint64_t mstime)
 		// The hardware renderer uses a different value range and clamps it to a single rotation
 		Level->hw_sky1pos = (float)(fmod((double(mstime) * Level->skyspeed1), 1024.) * (90. / 256.));
 		Level->hw_sky2pos = (float)(fmod((double(mstime) * Level->skyspeed2), 1024.) * (90. / 256.));
+		Level->hw_skymistpos = (float)(fmod((double(mstime) * Level->skymistspeed), 1024.) * (90. / 256.));
 	}
 }
 

src/scripting/vmthunks.cpp

@@ -1738,6 +1738,15 @@ DEFINE_ACTION_FUNCTION_NATIVE(_Sector, SetXOffset, SetXOffset)
 	 return 0;
  }
 
+ DEFINE_ACTION_FUNCTION(FLevelLocals, ChangeSkyMist)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(FLevelLocals);
+	 PARAM_INT(skymist);
+	 self->skymisttexture = FSetTextureID(skymist);
+	 InitSkyMap(self);
+	 return 0;
+ }
+
  DEFINE_ACTION_FUNCTION(FLevelLocals, StartIntermission)
  {
 	 PARAM_SELF_STRUCT_PROLOGUE(FLevelLocals);
@@ -2802,6 +2811,7 @@ DEFINE_FIELD_X(LevelInfo, level_info_t, NextMap)
 DEFINE_FIELD_X(LevelInfo, level_info_t, NextSecretMap)
 DEFINE_FIELD_X(LevelInfo, level_info_t, SkyPic1)
 DEFINE_FIELD_X(LevelInfo, level_info_t, SkyPic2)
+DEFINE_FIELD_X(LevelInfo, level_info_t, SkyMistPic)
 DEFINE_FIELD_X(LevelInfo, level_info_t, F1Pic)
 DEFINE_FIELD_X(LevelInfo, level_info_t, cluster)
 DEFINE_FIELD_X(LevelInfo, level_info_t, partime)
@@ -2817,6 +2827,7 @@ DEFINE_FIELD_X(LevelInfo, level_info_t, MapLabel)
 DEFINE_FIELD_X(LevelInfo, level_info_t, musicorder)
 DEFINE_FIELD_X(LevelInfo, level_info_t, skyspeed1)
 DEFINE_FIELD_X(LevelInfo, level_info_t, skyspeed2)
+DEFINE_FIELD_X(LevelInfo, level_info_t, skymistspeed)
 DEFINE_FIELD_X(LevelInfo, level_info_t, cdtrack)
 DEFINE_FIELD_X(LevelInfo, level_info_t, gravity)
 DEFINE_FIELD_X(LevelInfo, level_info_t, aircontrol)
@@ -2860,8 +2871,10 @@ DEFINE_FIELD(FLevelLocals, Music)
 DEFINE_FIELD(FLevelLocals, musicorder)
 DEFINE_FIELD(FLevelLocals, skytexture1)
 DEFINE_FIELD(FLevelLocals, skytexture2)
+DEFINE_FIELD(FLevelLocals, skymisttexture)
 DEFINE_FIELD(FLevelLocals, skyspeed1)
 DEFINE_FIELD(FLevelLocals, skyspeed2)
+DEFINE_FIELD(FLevelLocals, skymistspeed)
 DEFINE_FIELD(FLevelLocals, total_secrets)
 DEFINE_FIELD(FLevelLocals, found_secrets)
 DEFINE_FIELD(FLevelLocals, total_items)