- refactored sector portal data so that it does not rely on actors.

This is necessary because otherwise the level data cannot be serialized before the actors.

src/dobject.cpp

@@ -384,6 +384,15 @@ size_t DObject::StaticPointerSubstitution (DObject *old, DObject *notOld)
 			changed += players[i].FixPointers (old, notOld);
 	}
 
+	for (auto &s : sectorPortals)
+	{
+		if (s.mSkybox == old)
+		{
+			s.mSkybox = static_cast<ASkyViewpoint*>(notOld);
+			changed++;
+		}
+	}
+
 	// Go through sectors.
 	if (sectors != NULL)
 	{
@@ -392,8 +401,6 @@ size_t DObject::StaticPointerSubstitution (DObject *old, DObject *notOld)
 #define SECTOR_CHECK(f,t) \
 	if (sectors[i].f.p == static_cast<t *>(old)) { sectors[i].f = static_cast<t *>(notOld); changed++; }
 			SECTOR_CHECK( SoundTarget, AActor );
-			SECTOR_CHECK( SkyBoxes[sector_t::ceiling], ASkyViewpoint );
-			SECTOR_CHECK( SkyBoxes[sector_t::floor], ASkyViewpoint );
 			SECTOR_CHECK( SecActTarget, ASectorAction );
 			SECTOR_CHECK( floordata, DSectorEffect );
 			SECTOR_CHECK( ceilingdata, DSectorEffect );

src/dobjgc.cpp

@@ -327,7 +327,10 @@ static void MarkRoot()
 	DThinker::MarkRoots();
 	FCanvasTextureInfo::Mark();
 	Mark(DACSThinker::ActiveThinker);
-	Mark(level.DefaultSkybox);
+	for (auto &s : sectorPortals)
+	{
+		Mark(s.mSkybox);
+	}
 	// Mark dead bodies.
 	for (i = 0; i < BODYQUESIZE; ++i)
 	{
@@ -680,8 +683,6 @@ size_t DSectorMarker::PropagateMark()
 		{
 			sector_t *sec = &sectors[SecNum + i];
 			GC::Mark(sec->SoundTarget);
-			GC::Mark(sec->SkyBoxes[sector_t::ceiling]);
-			GC::Mark(sec->SkyBoxes[sector_t::floor]);
 			GC::Mark(sec->SecActTarget);
 			GC::Mark(sec->floordata);
 			GC::Mark(sec->ceilingdata);

src/farchive.h

@@ -298,6 +298,7 @@ template<> FArchive &operator<< (FArchive &arc, FStrifeDialogueNode *&node);
 template<> FArchive &operator<< (FArchive &arc, FSwitchDef* &sw);
 template<> FArchive &operator<< (FArchive &arc, FDoorAnimation* &da);
 FArchive &operator<< (FArchive &arc, FLinePortal &da);
+FArchive &operator<< (FArchive &arc, FSectorPortal &da);
 
 
 

src/g_level.cpp

@@ -1386,7 +1386,6 @@ void G_InitLevelLocals ()
 	NormalLight.ChangeFade (level.fadeto);
 
 	level.DefaultEnvironment = info->DefaultEnvironment;
-	level.DefaultSkybox = NULL;
 }
 
 //==========================================================================
@@ -1538,7 +1537,7 @@ void G_SerializeLevel (FArchive &arc, bool hubLoad)
 	P_SerializeSubsectors(arc);
 	StatusBar->Serialize (arc);
 
-	arc << level.DefaultSkybox << level.total_monsters << level.total_items << level.total_secrets;
+	arc << level.total_monsters << level.total_items << level.total_secrets;
 
 	// Does this level have custom translations?
 	FRemapTable *trans;

src/g_level.h

@@ -435,8 +435,6 @@ struct FLevelLocals
 	int			airsupply;
 	int			DefaultEnvironment;		// Default sound environment.
 
-	TObjPtr<class ASkyViewpoint> DefaultSkybox;
-
 	FSectorScrollValues	*Scrolls;		// NULL if no DScrollers in this level
 
 	SBYTE		WallVertLight;			// Light diffs for vert/horiz walls

src/g_shared/a_sharedglobal.h

@@ -91,14 +91,9 @@ public:
 class ASkyViewpoint : public AActor
 {
 	DECLARE_CLASS (ASkyViewpoint, AActor)
-	HAS_OBJECT_POINTERS
 public:
-	void Serialize (FArchive &arc);
 	void BeginPlay ();
 	void Destroy ();
-	bool bInSkybox;
-	bool bAlways;
-	TObjPtr<ASkyViewpoint> Mate;
 };
 
 // For an EE compatible linedef based definition.

src/g_shared/a_skies.cpp

@@ -38,49 +38,42 @@
 #include "p_lnspec.h"
 #include "farchive.h"
 #include "r_sky.h"
+#include "portal.h"
 
 // arg0 = Visibility*4 for this skybox
 
-IMPLEMENT_POINTY_CLASS (ASkyViewpoint)
+IMPLEMENT_CLASS (ASkyViewpoint)
-	DECLARE_POINTER(Mate)
-END_POINTERS
 
 // If this actor has no TID, make it the default sky box
 void ASkyViewpoint::BeginPlay ()
 {
 	Super::BeginPlay ();
 
-	if (tid == 0 && level.DefaultSkybox == NULL)
+	if (tid == 0 && sectorPortals[0].mSkybox == nullptr)
 	{
-		level.DefaultSkybox = this;
+		sectorPortals[0].mSkybox = this;
+		sectorPortals[0].mDestination = Sector;
 	}
-	special1 = SKYBOX_SKYVIEWPOINT;
-}
-
-void ASkyViewpoint::Serialize (FArchive &arc)
-{
-	Super::Serialize (arc);
-	arc << bInSkybox << bAlways << Mate;
 }
 
 void ASkyViewpoint::Destroy ()
 {
 	// remove all sector references to ourselves.
-	for (int i = 0; i <numsectors; i++)
+	for (int i = 0; i < numsectors; i++)
 	{
-		if (sectors[i].SkyBoxes[sector_t::floor] == this)
+		if (sectors[i].GetPortal(sector_t::floor)->mSkybox == this)
-		{
+			sectors[i].ClearPortal(sector_t::floor);
-			sectors[i].SkyBoxes[sector_t::floor] = NULL;
+		if (sectors[i].GetPortal(sector_t::ceiling)->mSkybox == this)
-		}
+			sectors[i].ClearPortal(sector_t::ceiling);
-		if (sectors[i].SkyBoxes[sector_t::ceiling] == this)
-		{
-			sectors[i].SkyBoxes[sector_t::ceiling] = NULL;
-		}
 	}
-	if (level.DefaultSkybox == this)
+	for (auto &s : sectorPortals)
 	{
-		level.DefaultSkybox = NULL;
+		if (s.mSkybox == this) s.mSkybox = 0;
+		// This is necessary to entirely disable EE-style skyboxes
+		// if their viewpoint gets deleted.
+		s.mFlags |= PORTSF_SKYFLATONLY;	
 	}
+
 	Super::Destroy();
 }
 
@@ -90,10 +83,8 @@ void ASkyCamCompat::BeginPlay()
 {
 	// Do not call the SkyViewpoint's super method because it would trash our setup
 	AActor::BeginPlay();
-	special1 = SKYBOX_SKYVIEWPOINT;
 }
 
-
 //---------------------------------------------------------------------------
 
 // arg0 = tid of matching SkyViewpoint
@@ -130,20 +121,18 @@ void ASkyPicker::PostBeginPlay ()
 
 	if (box == NULL && args[0] != 0)
 	{
-		Printf ("Can't find SkyViewpoint %d for sector %td\n",
+		Printf ("Can't find SkyViewpoint %d for sector %td\n", args[0], Sector - sectors);
-			args[0], Sector - sectors);
 	}
 	else
 	{
+		int boxindex = P_GetSkyboxPortal(box);
 		if (0 == (args[1] & 2))
 		{
-			Sector->SkyBoxes[sector_t::ceiling] = box;
+			Sector->Portals[sector_t::ceiling] = boxindex;
-			if (box == NULL) Sector->MoreFlags |= SECF_NOCEILINGSKYBOX;	// sector should ignore the level's default skybox
 		}
 		if (0 == (args[1] & 1))
 		{
-			Sector->SkyBoxes[sector_t::floor] = box;
+			Sector->Portals[sector_t::floor] = boxindex;
-			if (box == NULL) Sector->MoreFlags |= SECF_NOFLOORSKYBOX;	// sector should ignore the level's default skybox
 		}
 	}
 	Destroy ();
@@ -160,9 +149,6 @@ void AStackPoint::BeginPlay ()
 {
 	// Skip SkyViewpoint's initialization
 	AActor::BeginPlay ();
-
-	bAlways = true;
-	special1 = SKYBOX_STACKEDSECTORTHING;
 }
 
 //---------------------------------------------------------------------------

src/p_maputl.cpp

@@ -1629,10 +1629,10 @@ int FPathTraverse::PortalRelocate(intercept_t *in, int flags, DVector3 *optpos)
 	return saved->getPortal()->mType == PORTT_LINKED? 1:-1;
 }
 
-void FPathTraverse::PortalRelocate(AActor *portalthing, int flags, double hitfrac)
+void FPathTraverse::PortalRelocate(const DVector2 &displacement, int flags, double hitfrac)
 {
-	double hitx = trace.x + portalthing->Scale.X;
+	double hitx = trace.x + displacement.X;
-	double hity = trace.y + portalthing->Scale.Y;
+	double hity = trace.y + displacement.Y;
 	double endx = hitx + trace.dx;
 	double endy = hity + trace.dy;
 	intercepts.Resize(intercept_index);

src/p_maputl.h

@@ -373,7 +373,7 @@ public:
 	}
 	void init(double x1, double y1, double x2, double y2, int flags, double startfrac = 0);
 	int PortalRelocate(intercept_t *in, int flags, DVector3 *optpos = NULL);
-	void PortalRelocate(AActor *portalthing, int flags, double hitfrac);
+	void PortalRelocate(const DVector2 &disp, int flags, double hitfrac);
 	virtual ~FPathTraverse();
 	const divline_t &Trace() const { return trace; }
 

src/p_saveg.cpp

@@ -369,7 +369,7 @@ void P_SerializeWorld (FArchive &arc)
 			<< sec->sky
 			<< sec->MoreFlags
 			<< sec->Flags
-			<< sec->SkyBoxes[sector_t::floor] << sec->SkyBoxes[sector_t::ceiling]
+			<< sec->Portals[sector_t::floor] << sec->Portals[sector_t::ceiling]
 			<< sec->ZoneNumber;
 		arc	<< sec->interpolations[0]
 			<< sec->interpolations[1]
@@ -449,7 +449,7 @@ void P_SerializeWorld (FArchive &arc)
 		arc << zn->Environment;
 	}
 
-	arc << linePortals;
+	arc << linePortals << sectorPortals;
 	P_CollectLinkedPortals();
 }
 
@@ -565,22 +565,8 @@ void P_SerializePolyobjs (FArchive &arc)
 				I_Error ("UnarchivePolyobjs: Invalid polyobj tag");
 			}
 			arc << angle << delta << po->interpolation;
-			if (SaveVersion >= 4537)
+			arc << po->bBlocked;
-			{
+			arc << po->bHasPortals;
-				arc << po->bBlocked;
-			}
-			else
-			{
-				po->bBlocked = false;
-			}
-			if (SaveVersion >= 4538)
-			{
-				arc << po->bHasPortals;
-			}
-			else
-			{
-				po->bHasPortals = 0;
-			}
 
 			po->RotatePolyobj (angle, true);
 			delta -= po->StartSpot.pos;

src/p_sectors.cpp

@@ -32,6 +32,7 @@
 #include "r_utility.h"
 #include "a_sharedglobal.h"
 #include "p_local.h"
+#include "r_sky.h"
 #include "r_data/colormaps.h"
 
 
@@ -803,11 +804,13 @@ int sector_t::GetCeilingLight () const
 }
 
 
-ASkyViewpoint *sector_t::GetSkyBox(int which)
+FSectorPortal *sector_t::ValidatePortal(int which)
 {
-	if (SkyBoxes[which] != NULL) return barrier_cast<ASkyViewpoint*>(SkyBoxes[which]);
+	FSectorPortal *port = GetPortal(which);
-	if (MoreFlags & (SECF_NOFLOORSKYBOX << which)) return NULL;
+	if (port->mType == PORTS_SKYVIEWPOINT && port->mSkybox == nullptr) return nullptr;				// A skybox without a viewpoint is just a regular sky.
-	return level.DefaultSkybox;
+	if (PortalBlocksView(which)) return nullptr;													// disabled or obstructed linked portal.
+	if ((port->mFlags & PORTSF_SKYFLATONLY) && GetTexture(which) != skyflatnum) return nullptr;		// Skybox without skyflat texture
+	return port;
 }
 
 
@@ -873,13 +876,13 @@ int sector_t::GetTerrain(int pos) const
 
 void sector_t::CheckPortalPlane(int plane)
 {
-	AActor *portal = SkyBoxes[plane];
+	if (GetPortalType(plane) == PORTS_LINKEDPORTAL)
-	if (!portal || portal->special1 != SKYBOX_LINKEDPORTAL) return;
+	{
-
+		double portalh = GetPortalPlaneZ(plane);
-	double planeh = GetPlaneTexZF(plane);
+		double planeh = GetPlaneTexZF(plane);
-	int obstructed = PLANEF_OBSTRUCTED * (plane == sector_t::floor ?
+		int obstructed = PLANEF_OBSTRUCTED * (plane == sector_t::floor ? planeh > portalh : planeh < portalh);
-		planeh > portal->specialf1 : planeh < portal->specialf1);
+		planes[plane].Flags = (planes[plane].Flags  & ~PLANEF_OBSTRUCTED) | obstructed;
-	planes[plane].Flags = (planes[plane].Flags  & ~PLANEF_OBSTRUCTED) | obstructed;
+	}
 }
 
 //===========================================================================

src/p_spec.cpp

@@ -838,12 +838,13 @@ static void SetupFloorPortal (AStackPoint *point)
 	NActorIterator it (NAME_LowerStackLookOnly, point->tid);
 	sector_t *Sector = point->Sector;
 	ASkyViewpoint *skyv = static_cast<ASkyViewpoint*>(it.Next());
-	Sector->SkyBoxes[sector_t::floor] = skyv;
+	if (skyv != NULL)
-	if (skyv != NULL && skyv->bAlways)
 	{
-		skyv->Mate = point;
+		skyv->target = point;
 		if (Sector->GetAlphaF(sector_t::floor) == 1.)
 			Sector->SetAlpha(sector_t::floor, clamp(point->args[0], 0, 255) / 255.);
+
+		Sector->Portals[sector_t::floor] = P_GetStackPortal(skyv, sector_t::floor);
 	}
 }
 
@@ -852,12 +853,13 @@ static void SetupCeilingPortal (AStackPoint *point)
 	NActorIterator it (NAME_UpperStackLookOnly, point->tid);
 	sector_t *Sector = point->Sector;
 	ASkyViewpoint *skyv = static_cast<ASkyViewpoint*>(it.Next());
-	Sector->SkyBoxes[sector_t::ceiling] = skyv;
+	if (skyv != NULL)
-	if (skyv != NULL && skyv->bAlways)
 	{
-		skyv->Mate = point;
+		skyv->target = point;
 		if (Sector->GetAlphaF(sector_t::ceiling) == 1.)
 			Sector->SetAlpha(sector_t::ceiling, clamp(point->args[0], 0, 255) / 255.);
+
+		Sector->Portals[sector_t::ceiling] = P_GetStackPortal(skyv, sector_t::ceiling);
 	}
 }
 
@@ -881,42 +883,68 @@ void P_SetupPortals()
 		pt->special1 = 0;
 		points.Push(pt);
 	}
+	// the semantics here are incredibly lax so the final setup can only be done once all portals have been created,
+	// because later stackpoints will happily overwrite info in older ones, if there are multiple links.
+	for (auto &s : sectorPortals)
+	{
+		if (s.mType == PORTS_STACKEDSECTORTHING && s.mSkybox)
+		{
+			for (auto &ss : sectorPortals)
+			{
+				if (ss.mType == PORTS_STACKEDSECTORTHING && ss.mSkybox == s.mSkybox->target)
+				{
+					s.mPartner = (&ss) - &sectorPortals[0];
+				}
+			}
+		}
+	}
+	// Now we can finally set the displacement and delete the stackpoint reference.
+	for (auto &s : sectorPortals)
+	{
+		if (s.mType == PORTS_STACKEDSECTORTHING && s.mSkybox)
+		{
+			s.mDisplacement = s.mSkybox->Pos() - s.mSkybox->target->Pos();
+			s.mSkybox = NULL;
+		}
+	}
 }
 
-static void SetPortal(sector_t *sector, int plane, ASkyViewpoint *portal, double alpha)
+static void SetPortal(sector_t *sector, int plane, unsigned pnum, double alpha)
 {
 	// plane: 0=floor, 1=ceiling, 2=both
 	if (plane > 0)
 	{
-		if (sector->SkyBoxes[sector_t::ceiling] == NULL || !barrier_cast<ASkyViewpoint*>(sector->SkyBoxes[sector_t::ceiling])->bAlways)
+		if (sector->GetPortalType(sector_t::ceiling) == PORTS_SKYVIEWPOINT)
 		{
-			sector->SkyBoxes[sector_t::ceiling] = portal;
+			sector->Portals[sector_t::ceiling] = pnum;
 			if (sector->GetAlphaF(sector_t::ceiling) == 1.)
 				sector->SetAlpha(sector_t::ceiling, alpha);
 
-			if (!portal->bAlways) sector->SetTexture(sector_t::ceiling, skyflatnum);
+			if (sectorPortals[pnum].mFlags & PORTSF_SKYFLATONLY)
+				sector->SetTexture(sector_t::ceiling, skyflatnum);
 		}
 	}
 	if (plane == 2 || plane == 0)
 	{
-		if (sector->SkyBoxes[sector_t::floor] == NULL || !barrier_cast<ASkyViewpoint*>(sector->SkyBoxes[sector_t::floor])->bAlways)
+		if (sector->GetPortalType(sector_t::floor) == PORTS_SKYVIEWPOINT)
 		{
-			sector->SkyBoxes[sector_t::floor] = portal;
+			sector->Portals[sector_t::floor] = pnum;
 		}
 		if (sector->GetAlphaF(sector_t::floor) == 1.)
 			sector->SetAlpha(sector_t::floor, alpha);
 
-		if (!portal->bAlways) sector->SetTexture(sector_t::floor, skyflatnum);
+		if (sectorPortals[pnum].mFlags & PORTSF_SKYFLATONLY)
+			sector->SetTexture(sector_t::floor, skyflatnum);
 	}
 }
 
-static void CopyPortal(int sectortag, int plane, ASkyViewpoint *origin, double alpha, bool tolines)
+static void CopyPortal(int sectortag, int plane, unsigned pnum, double alpha, bool tolines)
 {
 	int s;
 	FSectorTagIterator itr(sectortag);
 	while ((s = itr.Next()) >= 0)
 	{
-		SetPortal(&sectors[s], plane, origin, alpha);
+		SetPortal(&sectors[s], plane, pnum, alpha);
 	}
 
 	for (int j=0;j<numlines;j++)
@@ -930,20 +958,21 @@ static void CopyPortal(int sectortag, int plane, ASkyViewpoint *origin, double a
 		{
 			if (lines[j].args[0] == 0)
 			{
-				SetPortal(lines[j].frontsector, plane, origin, alpha);
+				SetPortal(lines[j].frontsector, plane, pnum, alpha);
 			}
 			else
 			{
 				FSectorTagIterator itr(lines[j].args[0]);
 				while ((s = itr.Next()) >= 0)
 				{
-					SetPortal(&sectors[s], plane, origin, alpha);
+					SetPortal(&sectors[s], plane, pnum, alpha);
 				}
 			}
 		}
 	}
 }
 
+
 void P_SpawnPortal(line_t *line, int sectortag, int plane, int bytealpha, int linked)
 {
 	if (plane < 0 || plane > 2 || (linked && plane == 2)) return;
@@ -958,36 +987,10 @@ void P_SpawnPortal(line_t *line, int sectortag, int plane, int bytealpha, int li
 			lines[i].args[3] == 1)
 		{
 			// beware of overflows.
-			DVector3 pos1((line->v1->fX() + line->v2->fX()) / 2, (line->v1->fY() + line->v2->fY()) / 2, 0);
+			DVector2 pos1 = line->v1->fPos() + line->Delta() / 2;
-			DVector3 pos2((lines[i].v1->fX() + lines[i].v2->fX()) / 2, (lines[i].v1->fY() + lines[i].v2->fY()) / 2, 0);
+			DVector2 pos2 = lines[i].v1->fPos() + lines[i].Delta() / 2;
-			double z = linked ? line->frontsector->GetPlaneTexZF(plane) : 0;	// the map's sector height defines the portal plane for linked portals
+			unsigned pnum = P_GetPortal(linked ? PORTS_LINKEDPORTAL : PORTS_PORTAL, plane, line->frontsector, lines[i].frontsector, pos2 - pos1);
-
+			CopyPortal(sectortag, plane, pnum, bytealpha / 255., false);
-			double alpha = bytealpha / 255.;
-
-			AStackPoint *anchor = Spawn<AStackPoint>(pos1, NO_REPLACE);
-			AStackPoint *reference = Spawn<AStackPoint>(pos2, NO_REPLACE);
-
-			// In some situations it can happen that the sector here is not the frontsector of the anchor linedef,
-			// because some colinear node line with opposite direction causes this to be positioned on the wrong side.
-			// Fortunately these things will never move so it should be sufficient to set the intended sector directly.
-			anchor->Sector = line->frontsector;
-			reference->Sector = lines[i].frontsector;
-
-			reference->special1 = linked ? SKYBOX_LINKEDPORTAL : SKYBOX_PORTAL;
-			anchor->special1 = SKYBOX_ANCHOR;
-			// store the portal displacement in the unused scaleX/Y members of the portal reference actor.
-			anchor->Scale = -(reference->Scale = pos2 - pos1);
-			anchor->specialf1 = reference->specialf1 = z;
-
-			reference->Mate = anchor;
-			anchor->Mate = reference;
-
-			// This is so that the renderer can distinguish these portals from
-			// the ones spawned with the '*StackLookOnly' things.
-			reference->flags |= MF_JUSTATTACKED;
-			anchor->flags |= MF_JUSTATTACKED;
-
-			CopyPortal(sectortag, plane, reference, alpha, false);
 			return;
 		}
 	}
@@ -1012,7 +1015,8 @@ void P_SpawnSkybox(ASkyViewpoint *origin)
 			if (refline->special == Sector_SetPortal && refline->args[1] == 2)
 			{
 				// We found the setup linedef for this skybox, so let's use it for our init.
-				CopyPortal(refline->args[0], refline->args[2], origin, 0, true);
+				unsigned pnum = P_GetSkyboxPortal(origin);
+				CopyPortal(refline->args[0], refline->args[2], pnum, 0, true);
 				return;
 			}
 		}
@@ -1334,6 +1338,12 @@ void P_SpawnSpecials (void)
 			{
 				P_SpawnPortal(&lines[i], lines[i].args[0], lines[i].args[2], lines[i].args[4], lines[i].args[1]);
 			}
+			else if (lines[i].args[1] == 3 || lines[i].args[1] == 4)
+			{
+				line_t *line = &lines[i];
+				unsigned pnum = P_GetPortal(line->args[1] == 3 ? PORTS_PLANE : PORTS_HORIZON, line->args[2], line->frontsector, NULL, { 0,0 });
+				CopyPortal(line->args[0], line->args[2], pnum, 0, true);
+			}
 			break;
 
 		case Line_SetPortal:

src/p_trace.cpp

@@ -216,7 +216,7 @@ void FTraceInfo::EnterSectorPortal(FPathTraverse &pt, int position, double frac,
 	inshootthrough = true;
 	startfrac = frac;
 	EnterDist = enterdist;
-	pt.PortalRelocate(entersec->SkyBoxes[position], ptflags, frac);
+	pt.PortalRelocate(entersec->GetPortal(position)->mDisplacement, ptflags, frac);
 
 	if ((TraceFlags & TRACE_ReportPortals) && TraceCallback != NULL)
 	{
@@ -321,7 +321,7 @@ void FTraceInfo::Setup3DFloors()
 					{
 						CurSector->floorplane = *rover->top.plane;
 						CurSector->SetTexture(sector_t::floor, *rover->top.texture, false);
-						CurSector->SkyBoxes[sector_t::floor] = nullptr;
+						CurSector->ClearPortal(sector_t::floor);
 						bf = ff_top;
 					}
 				}
@@ -333,7 +333,7 @@ void FTraceInfo::Setup3DFloors()
 						CurSector->ceilingplane = *rover->bottom.plane;
 						CurSector->SetTexture(sector_t::ceiling, *rover->bottom.texture, false);
 						bc = ff_bottom;
-						CurSector->SkyBoxes[sector_t::ceiling] = nullptr;
+						CurSector->ClearPortal(sector_t::ceiling);
 					}
 				}
 				else
@@ -343,7 +343,7 @@ void FTraceInfo::Setup3DFloors()
 					{
 						CurSector->floorplane = *rover->bottom.plane;
 						CurSector->SetTexture(sector_t::floor, *rover->bottom.texture, false);
-						CurSector->SkyBoxes[sector_t::floor] = nullptr;
+						CurSector->ClearPortal(sector_t::floor);
 						bf = ff_bottom;
 					}
 
@@ -351,7 +351,7 @@ void FTraceInfo::Setup3DFloors()
 					{
 						CurSector->ceilingplane = *rover->top.plane;
 						CurSector->SetTexture(sector_t::ceiling, *rover->top.texture, false);
-						CurSector->SkyBoxes[sector_t::ceiling] = nullptr;
+						CurSector->ClearPortal(sector_t::ceiling);
 						bc = ff_top;
 					}
 					inshootthrough = false;
@@ -499,7 +499,7 @@ bool FTraceInfo::LineCheck(intercept_t *in, double dist, DVector3 hit)
 						{
 							entersector->floorplane = *rover->top.plane;
 							entersector->SetTexture(sector_t::floor, *rover->top.texture, false);
-							entersector->SkyBoxes[sector_t::floor] = NULL;
+							entersector->ClearPortal(sector_t::floor);
 							bf = ff_top;
 						}
 					}
@@ -510,7 +510,7 @@ bool FTraceInfo::LineCheck(intercept_t *in, double dist, DVector3 hit)
 						{
 							entersector->ceilingplane = *rover->bottom.plane;
 							entersector->SetTexture(sector_t::ceiling, *rover->bottom.texture, false);
-							entersector->SkyBoxes[sector_t::ceiling] = NULL;
+							entersector->ClearPortal(sector_t::ceiling);
 							bc = ff_bottom;
 						}
 					}

src/portal.cpp

@@ -64,6 +64,8 @@ FPortalBlockmap PortalBlockmap;
 TArray<FLinePortal> linePortals;
 TArray<FLinePortal*> linkedPortals;	// only the linked portals, this is used to speed up looking for them in P_CollectConnectedGroups.
 
+TArray<FSectorPortal> sectorPortals;
+
 //============================================================================
 //
 // This is used to mark processed portals for some collection functions.
@@ -213,6 +215,26 @@ FArchive &operator<< (FArchive &arc, FLinePortal &port)
 	return arc;
 }
 
+//============================================================================
+//
+// Save a sector portal for savegames.
+//
+//============================================================================
+
+FArchive &operator<< (FArchive &arc, FSectorPortal &port)
+{
+	arc << port.mType
+		<< port.mFlags
+		<< port.mPartner
+		<< port.mPlane
+		<< port.mOrigin
+		<< port.mDestination
+		<< port.mDisplacement
+		<< port.mPlaneZ
+		<< port.mSkybox;
+	return arc;
+}
+
 
 //============================================================================
 //
@@ -487,7 +509,7 @@ bool P_ChangePortal(line_t *ln, int thisid, int destid)
 
 //============================================================================
 //
-// clears all portal dat for a new level start
+// clears all portal data for a new level start
 //
 //============================================================================
 
@@ -496,9 +518,17 @@ void P_ClearPortals()
 	Displacements.Create(1);
 	linePortals.Clear();
 	linkedPortals.Clear();
+	sectorPortals.Resize(2);
+	// The first entry must always be the default skybox. This is what every sector gets by default.
+	memset(&sectorPortals[0], 0, sizeof(sectorPortals[0]));
+	sectorPortals[0].mType = PORTS_SKYVIEWPOINT;
+	sectorPortals[0].mFlags = PORTSF_SKYFLATONLY;
+	// The second entry will be the default sky. This is for forcing a regular sky through the skybox picker
+	memset(&sectorPortals[1], 0, sizeof(sectorPortals[0]));
+	sectorPortals[1].mType = PORTS_SKYVIEWPOINT;
+	sectorPortals[1].mFlags = PORTSF_SKYFLATONLY;
 }
 
-
 //============================================================================
 //
 // check if this line is between portal and the viewer. clip away if it is.
@@ -637,6 +667,74 @@ void P_TranslatePortalZ(line_t* src, double& z)
 	}
 }
 
+//============================================================================
+//
+// P_GetSkyboxPortal
+//
+// Gets a portal for a SkyViewpoint
+// If none exists yet, it will create a new one.
+//
+//============================================================================
+
+unsigned P_GetSkyboxPortal(ASkyViewpoint *actor)
+{
+	if (actor == NULL) return 1;	// this means a regular sky.
+	for (unsigned i = 0;i<sectorPortals.Size();i++)
+	{
+		if (sectorPortals[i].mSkybox == actor) return i;
+	}
+	unsigned i = sectorPortals.Reserve(1);
+	memset(&sectorPortals[i], 0, sizeof(sectorPortals[i]));
+	sectorPortals[i].mType = PORTS_SKYVIEWPOINT;
+	sectorPortals[i].mFlags = actor->GetClass()->IsDescendantOf(RUNTIME_CLASS(ASkyCamCompat)) ? 0 : PORTSF_SKYFLATONLY;
+	sectorPortals[i].mSkybox = actor;
+	sectorPortals[i].mDestination = actor->Sector;
+	return i;
+}
+
+//============================================================================
+//
+// P_GetPortal
+//
+// Creates a portal struct for a linedef-based portal
+//
+//============================================================================
+
+unsigned P_GetPortal(int type, int plane, sector_t *from, sector_t *to, const DVector2 &displacement)
+{
+	unsigned i = sectorPortals.Reserve(1);
+	memset(&sectorPortals[i], 0, sizeof(sectorPortals[i]));
+	sectorPortals[i].mType = type;
+	sectorPortals[i].mPlane = plane;
+	sectorPortals[i].mOrigin = from;
+	sectorPortals[i].mDestination = to;
+	sectorPortals[i].mDisplacement = displacement;
+	sectorPortals[i].mPlaneZ = type == PORTS_LINKEDPORTAL? from->GetPlaneTexZF(plane) : FLT_MAX;
+	return i;
+}
+
+//============================================================================
+//
+// P_GetStackPortal
+//
+// Creates a portal for a stacked sector thing
+//
+//============================================================================
+
+unsigned P_GetStackPortal(AActor *point, int plane)
+{
+	unsigned i = sectorPortals.Reserve(1);
+	memset(&sectorPortals[i], 0, sizeof(sectorPortals[i]));
+	sectorPortals[i].mType = PORTS_STACKEDSECTORTHING;
+	sectorPortals[i].mPlane = plane;
+	sectorPortals[i].mOrigin = point->target->Sector;
+	sectorPortals[i].mDestination = point->Sector;
+	sectorPortals[i].mPlaneZ = FLT_MAX;
+	sectorPortals[i].mSkybox = point;
+	return i;
+}
+
+
 //============================================================================
 //
 // P_GetOffsetPosition
@@ -756,35 +854,35 @@ static bool CollectSectors(int groupid, sector_t *origin)
 //
 //============================================================================
 
-static void AddDisplacementForPortal(AStackPoint *portal)
+static void AddDisplacementForPortal(FSectorPortal *portal)
 {
-	int thisgroup = portal->Mate->Sector->PortalGroup;
+	int thisgroup = portal->mOrigin->PortalGroup;
-	int othergroup = portal->Sector->PortalGroup;
+	int othergroup = portal->mDestination->PortalGroup;
 	if (thisgroup == othergroup)
 	{
-		Printf("Portal between sectors %d and %d has both sides in same group and will be disabled\n", portal->Sector->sectornum, portal->Mate->Sector->sectornum);
+		Printf("Portal between sectors %d and %d has both sides in same group and will be disabled\n", portal->mOrigin->sectornum, portal->mDestination->sectornum);
-		portal->special1 = portal->Mate->special1 = SKYBOX_PORTAL;
+		portal->mType = PORTS_PORTAL;
 		return;
 	}
 	if (thisgroup <= 0 || thisgroup >= Displacements.size || othergroup <= 0 || othergroup >= Displacements.size)
 	{
-		Printf("Portal between sectors %d and %d has invalid group and will be disabled\n", portal->Sector->sectornum, portal->Mate->Sector->sectornum);
+		Printf("Portal between sectors %d and %d has invalid group and will be disabled\n", portal->mOrigin->sectornum, portal->mDestination->sectornum);
-		portal->special1 = portal->Mate->special1 = SKYBOX_PORTAL;
+		portal->mType = PORTS_PORTAL;
 		return;
 	}
 
 	FDisplacement & disp = Displacements(thisgroup, othergroup);
 	if (!disp.isSet)
 	{
-		disp.pos = portal->Scale;
+		disp.pos = portal->mDisplacement;
 		disp.isSet = true;
 	}
 	else
 	{
-		if (disp.pos != portal->Scale)
+		if (disp.pos != portal->mDisplacement)
 		{
-			Printf("Portal between sectors %d and %d has displacement mismatch and will be disabled\n", portal->Sector->sectornum, portal->Mate->Sector->sectornum);
+			Printf("Portal between sectors %d and %d has displacement mismatch and will be disabled\n", portal->mOrigin->sectornum, portal->mDestination->sectornum);
-			portal->special1 = portal->Mate->special1 = SKYBOX_PORTAL;
+			portal->mType = PORTS_PORTAL;
 			return;
 		}
 	}
@@ -895,55 +993,43 @@ static bool ConnectGroups()
 
 void P_CreateLinkedPortals()
 {
-	TThinkerIterator<AStackPoint> it;
+	TArray<FSectorPortal *> orgs;
-	AStackPoint *mo;
-	TArray<AStackPoint *> orgs;
 	int id = 1;
 	bool bogus = false;
 
-	while ((mo = it.Next()))
+	for(auto &s : sectorPortals)
 	{
-		if (mo->special1 == SKYBOX_LINKEDPORTAL)
+		if (s.mType == PORTS_LINKEDPORTAL)
 		{
-			if (mo->Mate != NULL)
+			orgs.Push(&s);
-			{
-				orgs.Push(mo);
-				mo->reactiontime = ++id;
-			}
-			else
-			{
-				// this should never happen, but if it does, the portal needs to be removed
-				mo->Destroy();
-			}
 		}
 	}
 	id = 1;
 	if (orgs.Size() != 0)
 	{
-	for (int i = 0; i < numsectors; i++)
+		for (int i = 0; i < numsectors; i++)
-	{
-		for (int j = 0; j < 2; j++)
 		{
-			AActor *box = sectors[i].SkyBoxes[j];
+			for (int j = 0; j < 2; j++)
-			if (box != NULL && box->special1 == SKYBOX_LINKEDPORTAL)
 			{
-				secplane_t &plane = j == 0 ? sectors[i].floorplane : sectors[i].ceilingplane;
+				if (sectors[i].GetPortalType(j) == PORTS_LINKEDPORTAL)
-				if (plane.isSlope())
 				{
-					// The engine cannot deal with portals on a sloped plane.
+					secplane_t &plane = j == 0 ? sectors[i].floorplane : sectors[i].ceilingplane;
-					sectors[i].SkyBoxes[j] = NULL;
+					if (plane.isSlope())
-					Printf("Portal on %s of sector %d is sloped and will be disabled\n", j == 0 ? "floor" : "ceiling", i);
+					{
+						// The engine cannot deal with portals on a sloped plane.
+						sectors[i].ClearPortal(j);
+						Printf("Portal on %s of sector %d is sloped and will be disabled\n", j == 0 ? "floor" : "ceiling", i);
+					}
 				}
 			}
 		}
-	}
 
-	// Group all sectors, starting at each portal origin.
+		// Group all sectors, starting at each portal origin.
-	for (unsigned i = 0; i < orgs.Size(); i++)
+		for (unsigned i = 0; i < orgs.Size(); i++)
-	{
+		{
-		if (CollectSectors(id, orgs[i]->Sector)) id++;
+			if (CollectSectors(id, orgs[i]->mOrigin)) id++;
-		if (CollectSectors(id, orgs[i]->Mate->Sector)) id++;
+			if (CollectSectors(id, orgs[i]->mDestination)) id++;
-	}
+		}
 	}
 	for (unsigned i = 0; i < linePortals.Size(); i++)
 	{
@@ -960,17 +1046,9 @@ void P_CreateLinkedPortals()
 	{
 		for (int j = 0; j < 2; j++)
 		{
-			ASkyViewpoint *box = barrier_cast<ASkyViewpoint*>(sectors[i].SkyBoxes[j]);
+			if (sectors[i].GetPortalType(j) == PORTS_LINKEDPORTAL && sectors[i].PortalGroup == 0)
-			if (box != NULL)
 			{
-				if (box->special1 == SKYBOX_LINKEDPORTAL && sectors[i].PortalGroup == 0)
+				CollectSectors(sectors[i].GetOppositePortalGroup(j), &sectors[i]);
-				{
-					// Note: the linked actor will be on the other side of the portal.
-					// To get this side's group we will have to look at the mate object.
-					CollectSectors(box->Mate->Sector->PortalGroup, &sectors[i]);
-					// We cannot process the backlink here because all we can access is the anchor object
-					// If necessary that will have to be done for the other side's portal.
-				}
 			}
 		}
 	}
@@ -1060,11 +1138,11 @@ void P_CreateLinkedPortals()
 				double fp = sectors[i].floorplane.fD();
 				if (cp < fp || fz == fp)
 				{
-					sectors[i].SkyBoxes[sector_t::ceiling] = NULL;
+					sectors[i].ClearPortal(sector_t::ceiling);
 				}
 				else
 				{
-					sectors[i].SkyBoxes[sector_t::floor] = NULL;
+					sectors[i].ClearPortal(sector_t::floor);
 				}
 			}
 		}

src/portal.h

@@ -6,6 +6,7 @@
 #include "m_bbox.h"
 
 struct FPortalGroupArray;
+class ASkyViewpoint;
 //============================================================================
 //
 // This table holds the offsets for the different parts of a map
@@ -173,8 +174,6 @@ enum
 //============================================================================
 //
 // All information about a line-to-line portal (all types)
-// There is no structure for sector plane portals because for historic
-// reasons those use actors to connect.
 //
 //============================================================================
 
@@ -190,10 +189,61 @@ struct FLinePortal
 	DAngle mAngleDiff;
 	double mSinRot;
 	double mCosRot;
+	void *mRenderData;
 };
 
 extern TArray<FLinePortal> linePortals;
 
+//============================================================================
+//
+// All information about a sector plane portal
+//
+//============================================================================
+
+enum
+{
+	PORTS_SKYVIEWPOINT = 0,		// a regular skybox
+	PORTS_STACKEDSECTORTHING,	// stacked sectors with the thing method
+	PORTS_PORTAL,				// stacked sectors with Sector_SetPortal
+	PORTS_LINKEDPORTAL,			// linked portal (interactive)
+	PORTS_PLANE,				// EE-style plane portal (not implemented in SW renderer)
+	PORTS_HORIZON,				// EE-style horizon portal (not implemented in SW renderer)
+};
+
+enum
+{
+	PORTSF_SKYFLATONLY = 1,				// portal is only active on skyflatnum
+	PORTSF_INSKYBOX = 2,				// to avoid recursion
+};
+
+struct FSectorPortal
+{
+	int mType;
+	int mFlags;
+	unsigned mPartner;
+	int mPlane;
+	sector_t *mOrigin;
+	sector_t *mDestination;
+	DVector2 mDisplacement;
+	double mPlaneZ;
+	TObjPtr<AActor> mSkybox;
+	void *mRenderData;
+
+	bool MergeAllowed() const
+	{
+		// For thing based stack sectors and regular skies the portal has no relevance for merging visplanes.
+		return (mType == PORTS_STACKEDSECTORTHING || (mType == PORTS_SKYVIEWPOINT && (mFlags & PORTSF_SKYFLATONLY)));
+	}
+};
+
+extern TArray<FSectorPortal> sectorPortals;
+
+//============================================================================
+//
+// Functions
+//
+//============================================================================
+
 void P_ClearPortals();
 void P_SpawnLinePortal(line_t* line);
 void P_FinalizePortals();
@@ -205,6 +255,9 @@ inline int P_NumPortalGroups()
 {
 	return Displacements.size;
 }
+unsigned P_GetSkyboxPortal(ASkyViewpoint *actor);
+unsigned P_GetPortal(int type, int plane, sector_t *orgsec, sector_t *destsec, const DVector2 &displacement);
+unsigned P_GetStackPortal(AActor *point, int plane);
 
 
 /* code ported from prototype */

src/r_bsp.cpp

@@ -515,18 +515,18 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec,
 
 bool R_SkyboxCompare(sector_t *frontsector, sector_t *backsector)
 {
-	AActor *frontc = frontsector->SkyBoxes[sector_t::ceiling];
+	FSectorPortal *frontc = frontsector->GetPortal(sector_t::ceiling);
-	AActor *frontf = frontsector->SkyBoxes[sector_t::floor];
+	FSectorPortal *frontf = frontsector->GetPortal(sector_t::floor);
-	AActor *backc = backsector->SkyBoxes[sector_t::ceiling];
+	FSectorPortal *backc = backsector->GetPortal(sector_t::ceiling);
-	AActor *backf = backsector->SkyBoxes[sector_t::floor];
+	FSectorPortal *backf = backsector->GetPortal(sector_t::floor);
 
 	// return true if any of the planes has a linedef-based portal (unless both sides have the same one.
 	// Ideally this should also check thing based portals but the omission of this check had been abused to hell and back for those.
 	// (Note: This may require a compatibility option if some maps ran into this for line based portals as well.)
-	if (frontc != NULL && (frontc->special1 == SKYBOX_PORTAL || frontc->special1 == SKYBOX_LINKEDPORTAL)) return (frontc != backc);
+	if (!frontc->MergeAllowed()) return (frontc != backc);
-	if (frontf != NULL && (frontf->special1 == SKYBOX_PORTAL || frontf->special1 == SKYBOX_LINKEDPORTAL)) return (frontf != backf);
+	if (!frontf->MergeAllowed()) return (frontf != backf);
-	if (backc != NULL && (backc->special1 == SKYBOX_PORTAL || backc->special1 == SKYBOX_LINKEDPORTAL)) return true;
+	if (!backc->MergeAllowed()) return true;
-	if (backf != NULL && (backf->special1 == SKYBOX_PORTAL || backf->special1 == SKYBOX_LINKEDPORTAL)) return true;
+	if (!backf->MergeAllowed()) return true;
 	return false;
 }
 
@@ -1046,7 +1046,7 @@ void R_Subsector (subsector_t *sub)
 	int          ceilinglightlevel;		// killough 4/11/98
 	bool		 outersubsector;
 	int	fll, cll, position;
-	ASkyViewpoint *skybox;
+	FSectorPortal *portal;
 
 	// kg3D - fake floor stuff
 	visplane_t *backupfp;
@@ -1114,12 +1114,11 @@ void R_Subsector (subsector_t *sub)
 		basecolormap = frontsector->ColorMap;
 	}
 
-	skybox = frontsector->GetSkyBox(sector_t::ceiling);
+	portal = frontsector->ValidatePortal(sector_t::ceiling);
-	if (skybox != NULL && skybox->special1 >= SKYBOX_PLANE) skybox = NULL;	// skip unsupported portal types
 
 	ceilingplane = frontsector->ceilingplane.PointOnSide(viewx, viewy, viewz) > 0 ||
 		frontsector->GetTexture(sector_t::ceiling) == skyflatnum ||
-		(skybox != NULL && skybox->bAlways) ||
+		portal != NULL ||
 		(frontsector->heightsec && 
 		 !(frontsector->heightsec->MoreFlags & SECF_IGNOREHEIGHTSEC) &&
 		 frontsector->heightsec->GetTexture(sector_t::floor) == skyflatnum) ?
@@ -1134,7 +1133,7 @@ void R_Subsector (subsector_t *sub)
 					frontsector->GetYScale(sector_t::ceiling),
 					frontsector->GetAngle(sector_t::ceiling),
 					frontsector->sky,
-					skybox
+					portal
 					) : NULL;
 
 	if (fixedlightlev < 0 && frontsector->e && frontsector->e->XFloor.lightlist.Size())
@@ -1156,12 +1155,11 @@ void R_Subsector (subsector_t *sub)
 	// killough 3/7/98: Add (x,y) offsets to flats, add deep water check
 	// killough 3/16/98: add floorlightlevel
 	// killough 10/98: add support for skies transferred from sidedefs
-	skybox = frontsector->GetSkyBox(sector_t::floor);
+	portal = frontsector->ValidatePortal(sector_t::floor);
-	if (skybox != NULL && skybox->special1 >= SKYBOX_PLANE) skybox = NULL;	// skip unsupported portal types
 
 	floorplane = frontsector->floorplane.PointOnSide(viewx, viewy, viewz) > 0 || // killough 3/7/98
 		frontsector->GetTexture(sector_t::floor) == skyflatnum ||
-		(skybox != NULL && skybox->bAlways) ||
+		portal != NULL ||
 		(frontsector->heightsec &&
 		 !(frontsector->heightsec->MoreFlags & SECF_IGNOREHEIGHTSEC) &&
 		 frontsector->heightsec->GetTexture(sector_t::ceiling) == skyflatnum) ?
@@ -1176,7 +1174,7 @@ void R_Subsector (subsector_t *sub)
 					frontsector->GetYScale(sector_t::floor),
 					frontsector->GetAngle(sector_t::floor),
 					frontsector->sky,
-					skybox
+					portal
 					) : NULL;
 
 	// kg3D - fake planes rendering

src/r_defs.h

@@ -58,19 +58,6 @@ enum
 extern size_t MaxDrawSegs;
 struct FDisplacement;
 
-
-enum
-{
-	SKYBOX_ANCHOR = -1,
-	SKYBOX_SKYVIEWPOINT = 0,				// a regular skybox
-	SKYBOX_STACKEDSECTORTHING,	// stacked sectors with the thing method
-	SKYBOX_PORTAL,				// stacked sectors with Sector_SetPortal
-	SKYBOX_LINKEDPORTAL,		// linked portal (interactive)
-	SKYBOX_PLANE,				// EE-style plane portal (not implemented in SW renderer)
-	SKYBOX_HORIZON,				// EE-style horizon portal (not implemented in SW renderer)
-};
-
-
 //
 // INTERNAL MAP TYPES
 //	used by play and refresh
@@ -499,8 +486,6 @@ enum
 	SECF_UNDERWATERMASK	= 32+64,
 	SECF_DRAWN			= 128,	// sector has been drawn at least once
 	SECF_HIDDEN			= 256,	// Do not draw on textured automap
-	SECF_NOFLOORSKYBOX	= 512,	// force use of regular sky 
-	SECF_NOCEILINGSKYBOX	= 1024,	// force use of regular sky (do not separate from NOFLOORSKYBOX!!!)
 };
 
 enum
@@ -668,7 +653,7 @@ public:
 
 	DInterpolation *SetInterpolation(int position, bool attach);
 
-	ASkyViewpoint *GetSkyBox(int which);
+	FSectorPortal *ValidatePortal(int which);
 	void CheckPortalPlane(int plane);
 
 	enum
@@ -930,8 +915,7 @@ public:
 
 	bool PortalBlocksView(int plane)
 	{
-		if (SkyBoxes[plane] == NULL) return true;
+		if (GetPortalType(plane) != PORTS_LINKEDPORTAL) return false;
-		if (GetPortalType(plane) != SKYBOX_LINKEDPORTAL) return false;
 		return !!(planes[plane].Flags & (PLANEF_NORENDER | PLANEF_DISABLED | PLANEF_OBSTRUCTED));
 	}
 
@@ -952,28 +936,37 @@ public:
 
 	bool PortalIsLinked(int plane)
 	{
-		return (SkyBoxes[plane] != NULL && GetPortalType(plane) == SKYBOX_LINKEDPORTAL);
+		return (GetPortalType(plane) == PORTS_LINKEDPORTAL);
+	}
+
+	void ClearPortal(int plane)
+	{
+		Portals[plane] = 0;
+	}
+
+	FSectorPortal *GetPortal(int plane)
+	{
+		return &sectorPortals[Portals[plane]];
 	}
 
-	// These intentionally do not validate the SkyBoxes pointers.
 	double GetPortalPlaneZ(int plane)
 	{
-		return SkyBoxes[plane]->specialf1;
+		return sectorPortals[Portals[plane]].mPlaneZ;
 	}
 
 	DVector2 GetPortalDisplacement(int plane)
 	{
-		return SkyBoxes[plane]->Scale;
+		return sectorPortals[Portals[plane]].mDisplacement;
 	}
 
 	int GetPortalType(int plane)
 	{
-		return SkyBoxes[plane]->special1;
+		return sectorPortals[Portals[plane]].mType;
 	}
 
 	int GetOppositePortalGroup(int plane)
 	{
-		return SkyBoxes[plane]->Sector->PortalGroup;
+		return sectorPortals[Portals[plane]].mDestination->PortalGroup;
 	}
 
 	int GetTerrain(int pos) const;
@@ -1083,9 +1076,8 @@ public:
 	// occurs, SecActTarget's TriggerAction method is called.
 	TObjPtr<ASectorAction> SecActTarget;
 
-	// [RH] The sky box to render for this sector. NULL means use a
+	// [RH] The portal or skybox to render for this sector.
-	// regular sky.
+	unsigned Portals[2];
-	TObjPtr<AActor> SkyBoxes[2];
 	int PortalGroup;
 
 	int							sectornum;			// for comparing sector copies

src/r_main.cpp

@@ -693,7 +693,7 @@ void R_EnterPortal (PortalDrawseg* pds, int depth)
 	fixed_t starty = viewy;
 	fixed_t startz = viewz;
 	DVector3 savedpath[2] = { ViewPath[0], ViewPath[1] };
-	int savedvisibility = camera->renderflags & RF_INVISIBLE;
+	int savedvisibility = camera? camera->renderflags & RF_INVISIBLE : 0;
 
 	CurrentPortalUniq++;
 
@@ -746,7 +746,7 @@ void R_EnterPortal (PortalDrawseg* pds, int depth)
 		viewz = FLOAT2FIXED(view.Z);
 		viewangle = va.BAMs();
 
-		if (!r_showviewer)
+		if (!r_showviewer && camera)
 		{
 			double distp = (ViewPath[0] - ViewPath[1]).Length();
 			if (distp > EQUAL_EPSILON)
@@ -802,11 +802,11 @@ void R_EnterPortal (PortalDrawseg* pds, int depth)
 	InSubsector = NULL;
 	R_RenderBSPNode (nodes + numnodes - 1);
 	R_3D_ResetClip(); // reset clips (floor/ceiling)
-	if (!savedvisibility) camera->renderflags &= ~RF_INVISIBLE;
+	if (!savedvisibility && camera) camera->renderflags &= ~RF_INVISIBLE;
 
 	PlaneCycles.Clock();
 	R_DrawPlanes ();
-	R_DrawSkyBoxes ();
+	R_DrawPortals ();
 	PlaneCycles.Unclock();
 
 	fixed_t vzp = viewz;
@@ -961,7 +961,7 @@ void R_RenderActorView (AActor *actor, bool dontmaplines)
 	{
 		PlaneCycles.Clock();
 		R_DrawPlanes ();
-		R_DrawSkyBoxes ();
+		R_DrawPortals ();
 		PlaneCycles.Unclock();
 
 		// [RH] Walk through mirrors

src/r_plane.cpp

@@ -584,7 +584,7 @@ static visplane_t *new_visplane (unsigned hash)
 visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightlevel, fixed_t alpha, bool additive,
 						 fixed_t xoffs, fixed_t yoffs,
 						 fixed_t xscale, fixed_t yscale, angle_t angle,
-						 int sky, ASkyViewpoint *skybox)
+						 int sky, FSectorPortal *portal)
 {
 	secplane_t plane;
 	visplane_t *check;
@@ -606,9 +606,9 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 		// same column but separated by a wall. If they both try to reside in the
 		// same visplane, then only the floor sky will be drawn.
 		plane.set(0., 0., height.fC(), 0.);
-		isskybox = skybox != NULL && !skybox->bInSkybox;
+		isskybox = portal != NULL && !(portal->mFlags & PORTSF_INSKYBOX);
 	}
-	else if (skybox != NULL && skybox->bAlways && !skybox->bInSkybox)
+	else if (portal != NULL && !(portal->mFlags & PORTSF_INSKYBOX))
 	{
 		plane = height;
 		isskybox = true;
@@ -622,7 +622,7 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 		// and ->alpha is for stacked sectors
 		if (fake3D & (FAKE3D_FAKEFLOOR|FAKE3D_FAKECEILING)) sky = 0x80000000 | fakeAlpha;
 		else sky = 0;	// not skyflatnum so it can't be a sky
-		skybox = NULL;
+		portal = NULL;
 		alpha = OPAQUE;
 	}
 
@@ -633,9 +633,9 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 	{
 		if (isskybox)
 		{
-			if (skybox == check->skybox && plane == check->height)
+			if (portal == check->portal && plane == check->height)
 			{
-				if (skybox->Mate != NULL)
+				if (portal->mType != PORTS_SKYVIEWPOINT)
 				{ // This skybox is really a stacked sector, so we need to
 				  // check even more.
 					if (check->extralight == stacked_extralight &&
@@ -645,7 +645,7 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 						check->viewz == stacked_viewz &&
 						(
 							// headache inducing logic... :(
-							(!(skybox->flags & MF_JUSTATTACKED)) ||
+							(portal->mType != PORTS_STACKEDSECTORTHING) ||
 							(
 								check->Alpha == alpha &&
 								check->Additive == additive &&
@@ -710,7 +710,7 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 	check->angle = angle;
 	check->colormap = basecolormap;		// [RH] Save colormap
 	check->sky = sky;
-	check->skybox = skybox;
+	check->portal = portal;
 	check->left = viewwidth;			// Was SCREENWIDTH -- killough 11/98
 	check->right = 0;
 	check->extralight = stacked_extralight;
@@ -781,7 +781,7 @@ visplane_t *R_CheckPlane (visplane_t *pl, int start, int stop)
 		// make a new visplane
 		unsigned hash;
 
-		if (pl->skybox != NULL && !pl->skybox->bInSkybox && (pl->picnum == skyflatnum || pl->skybox->bAlways) && viewactive)
+		if (pl->portal != NULL && !(pl->portal->mFlags & PORTSF_INSKYBOX) && viewactive)
 		{
 			hash = MAXVISPLANES;
 		}
@@ -800,7 +800,7 @@ visplane_t *R_CheckPlane (visplane_t *pl, int start, int stop)
 		new_pl->yscale = pl->yscale;
 		new_pl->angle = pl->angle;
 		new_pl->colormap = pl->colormap;
-		new_pl->skybox = pl->skybox;
+		new_pl->portal = pl->portal;
 		new_pl->extralight = pl->extralight;
 		new_pl->visibility = pl->visibility;
 		new_pl->viewx = pl->viewx;
@@ -1160,7 +1160,7 @@ void R_DrawSinglePlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 
 //==========================================================================
 //
-// R_DrawSkyBoxes
+// R_DrawPortals
 //
 // Draws any recorded sky boxes and then frees them.
 //
@@ -1181,7 +1181,7 @@ void R_DrawSinglePlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 CVAR (Bool, r_skyboxes, true, 0)
 static int numskyboxes;
 
-void R_DrawSkyBoxes ()
+void R_DrawPortals ()
 {
 	static TArray<size_t> interestingStack;
 	static TArray<ptrdiff_t> drawsegStack;
@@ -1221,7 +1221,7 @@ void R_DrawSkyBoxes ()
 		visplanes[MAXVISPLANES] = pl->next;
 		pl->next = NULL;
 
-		if (pl->right < pl->left || !r_skyboxes || numskyboxes == MAX_SKYBOX_PLANES)
+		if (pl->right < pl->left || !r_skyboxes || numskyboxes == MAX_SKYBOX_PLANES || pl->portal == NULL)
 		{
 			R_DrawSinglePlane (pl, OPAQUE, false, false);
 			*freehead = pl;
@@ -1231,14 +1231,15 @@ void R_DrawSkyBoxes ()
 
 		numskyboxes++;
 
-		ASkyViewpoint *sky = pl->skybox;
+		FSectorPortal *port = pl->portal;
-		ASkyViewpoint *mate = sky->Mate;
+		switch (port->mType)
-
+		{
-		if (mate == NULL)
+		case PORTS_SKYVIEWPOINT:
 		{
 			// Don't let gun flashes brighten the sky box
+			ASkyViewpoint *sky = barrier_cast<ASkyViewpoint*>(port->mSkybox);
 			extralight = 0;
-			R_SetVisibility (sky->args[0] * 0.25f);
+			R_SetVisibility(sky->args[0] * 0.25f);
 
 			DVector3 viewpos = sky->InterpolatedPosition(r_TicFracF);
 			viewx = FLOAT2FIXED(viewpos.X);
@@ -1247,23 +1248,40 @@ void R_DrawSkyBoxes ()
 			viewangle = savedangle + (sky->PrevAngles.Yaw + deltaangle(sky->PrevAngles.Yaw, sky->Angles.Yaw) * r_TicFracF).BAMs();
 
 			R_CopyStackedViewParameters();
+			break;
 		}
-		else
+
-		{
+		case PORTS_STACKEDSECTORTHING:
+		case PORTS_PORTAL:
+		case PORTS_LINKEDPORTAL:
 			extralight = pl->extralight;
 			R_SetVisibility (pl->visibility);
-			viewx = pl->viewx + FLOAT2FIXED(-sky->Mate->X() + sky->X());
+			viewx = pl->viewx + FLOAT2FIXED(port->mDisplacement.X);
-			viewy = pl->viewy + FLOAT2FIXED(-sky->Mate->Y() + sky->Y());
+			viewy = pl->viewy + FLOAT2FIXED(port->mDisplacement.Y);
 			viewz = pl->viewz;
 			viewangle = pl->viewangle;
+			break;
+
+		case PORTS_HORIZON:
+		case PORTS_PLANE:
+			// not implemented yet
+
+		default:
+			R_DrawSinglePlane(pl, OPAQUE, false, false);
+			*freehead = pl;
+			freehead = &pl->next;
+			numskyboxes--;
+			continue;
 		}
+
 		ViewAngle = AngleToFloat(viewangle);
 		ViewPos = { FIXED2DBL(viewx), FIXED2DBL(viewy), FIXED2DBL(viewz) };
 
-		sky->bInSkybox = true;
+		port->mFlags |= PORTSF_INSKYBOX;
-		if (mate != NULL) mate->bInSkybox = true;
+		if (port->mPartner > 0) sectorPortals[port->mPartner].mFlags |= PORTSF_INSKYBOX;
-		camera = sky;
+		camera = NULL;
-		viewsector = sky->Sector;
+		viewsector = port->mDestination;
+		assert(viewsector != NULL);
 		R_SetViewAngle ();
 		validcount++;	// Make sure we see all sprites
 
@@ -1324,8 +1342,8 @@ void R_DrawSkyBoxes ()
 		R_3D_ResetClip(); // reset clips (floor/ceiling)
 		R_DrawPlanes ();
 
-		sky->bInSkybox = false;
+		port->mFlags &= ~PORTSF_INSKYBOX;
-		if (mate != NULL) mate->bInSkybox = false;
+		if (port->mPartner > 0) sectorPortals[port->mPartner].mFlags &= ~PORTSF_INSKYBOX;
 	}
 
 	// Draw all the masked textures in a second pass, in the reverse order they

src/r_plane.h

@@ -43,7 +43,7 @@ struct visplane_s
 	fixed_t		xscale, yscale;		// [RH] Support flat scaling
 	angle_t		angle;				// [RH] Support flat rotation
 	int			sky;
-	ASkyViewpoint *skybox;			// [RH] Support sky boxes
+	FSectorPortal *portal;			// [RH] Support sky boxes
 
 	// [RH] This set of variables copies information from the time when the
 	// visplane is created. They are only used by stacks so that you can
@@ -88,7 +88,7 @@ void R_DeinitPlanes ();
 void R_ClearPlanes (bool fullclear);
 
 int R_DrawPlanes ();
-void R_DrawSkyBoxes ();
+void R_DrawPortals ();
 void R_DrawSkyPlane (visplane_t *pl);
 void R_DrawNormalPlane (visplane_t *pl, fixed_t alpha, bool additive, bool masked);
 void R_DrawTiltedPlane (visplane_t *pl, fixed_t alpha, bool additive, bool masked);
@@ -106,7 +106,7 @@ visplane_t *R_FindPlane
   fixed_t		yscale,
   angle_t		angle,
   int			sky,
-  ASkyViewpoint *skybox);
+  FSectorPortal *portal);
 
 visplane_t *R_CheckPlane (visplane_t *pl, int start, int stop);
 

src/r_things.cpp

@@ -1536,6 +1536,7 @@ void R_DrawPlayerSprites ()
 	F3DFloor *rover;
 
 	if (!r_drawplayersprites ||
+		!camera ||
 		!camera->player ||
 		(players[consoleplayer].cheats & CF_CHASECAM) ||
 		(r_deathcamera && camera->health <= 0))

src/version.h

@@ -72,11 +72,11 @@ const char *GetVersionString();
 // SAVESIG should match SAVEVER.
 
 // MINSAVEVER is the minimum level snapshot version that can be loaded.
-#define MINSAVEVER	4536
+#define MINSAVEVER	4539
 
 // Use 4500 as the base git save version, since it's higher than the
 // SVN revision ever got.
-#define SAVEVER 4538
+#define SAVEVER 4539
 
 #define SAVEVERSTRINGIFY2(x) #x
 #define SAVEVERSTRINGIFY(x) SAVEVERSTRINGIFY2(x)

wadsrc/static/xlat/eternity.txt

@@ -39,13 +39,13 @@ enum
 282 = 0,	Sector_Attach3DMidtex(tag, 0, 1) // "3DMidTex_MoveWithCeiling"
 
 // Plane portals are not supported in ZDoom, though they probably wouldn't be too hard to implement.
-283 = 0,	Unsupported() // "Portal_PlaneCeiling"
+283 = 0,	Sector_SetPortal(tag,3, 1, 0, 0) // "Portal_PlaneCeiling"
-284 = 0,	Unsupported() // "Portal_PlaneFloor"
+284 = 0,	Sector_SetPortal(tag,3, 0, 0, 0) // "Portal_PlaneFloor"
-285 = 0,	Unsupported() // "Portal_PlaneFloorCeiling"
+285 = 0,	Sector_SetPortal(tag,3, 2, 0, 0) // "Portal_PlaneFloorCeiling"
-286 = 0,	Unsupported() // "Portal_HorizonCeiling"
+286 = 0,	Sector_SetPortal(tag,4, 1, 0, 0) // "Portal_HorizonCeiling"
-287 = 0,	Unsupported() // "Portal_HorizonFloor"
+287 = 0,	Sector_SetPortal(tag,4, 0, 0, 0) // "Portal_HorizonFloor"
-288 = 0,	Unsupported() // "Portal_HorizonFloorCeiling"
+288 = 0,	Sector_SetPortal(tag,4, 2, 0, 0) // "Portal_HorizonFloorCeiling"
-289 = 0,	Unsupported() // "Portal_LineTransfer"
+289 = 0,	Sector_SetPortal(0, 5, 0, tag) // "Portal_LineTransfer"
 
 // Skybox portals
 290 = 0,	Sector_SetPortal(tag, 2, 1, 1, 0) // "Portal_SkyboxCeiling"