- wrap access to portal properties into sector_t:: member functions.

src/p_effect.cpp

@@ -287,22 +287,21 @@ void P_ThinkParticles ()
 		particle->Pos.Z += particle->Vel.Z;
 		particle->Vel += particle->Acc;
 		particle->subsector = R_PointInSubsector(particle->Pos);
+		sector_t *s = particle->subsector->sector;
 		// Handle crossing a sector portal.
-		if (!particle->subsector->sector->PortalBlocksMovement(sector_t::ceiling))
+		if (!s->PortalBlocksMovement(sector_t::ceiling))
 		{
-			AActor *skybox = particle->subsector->sector->SkyBoxes[sector_t::ceiling];
+			if (particle->Pos.Z > s->GetPortalPlaneZ(sector_t::ceiling))
-			if (particle->Pos.Z > skybox->specialf1)
 			{
-				particle->Pos += skybox->Scale;
+				particle->Pos += s->GetPortalDisplacement(sector_t::ceiling);
 				particle->subsector = NULL;
 			}
 		}
-		else if (!particle->subsector->sector->PortalBlocksMovement(sector_t::floor))
+		else if (!s->PortalBlocksMovement(sector_t::floor))
 		{
-			AActor *skybox = particle->subsector->sector->SkyBoxes[sector_t::floor];
+			if (particle->Pos.Z < s->GetPortalPlaneZ(sector_t::floor))
-			if (particle->Pos.Z < skybox->specialf1)
 			{
-				particle->Pos += skybox->Scale;
+				particle->Pos += s->GetPortalDisplacement(sector_t::floor);
 				particle->subsector = NULL;
 			}
 		}

src/p_enemy.cpp

@@ -162,12 +162,12 @@ void P_RecursiveSound (sector_t *sec, AActor *soundtarget, bool splash, int soun
 		// I wish there was a better method to do this than randomly looking through the portal at a few places...
 		if (checkabove)
 		{
-			sector_t *upper = P_PointInSector(check->v1->fPos() + check->Delta() / 2 + sec->SkyBoxes[sector_t::ceiling]->Scale);
+			sector_t *upper = P_PointInSector(check->v1->fPos() + check->Delta() / 2 + sec->GetPortalDisplacement(sector_t::ceiling));
 			P_RecursiveSound(upper, soundtarget, splash, soundblocks, emitter, maxdist);
 		}
 		if (checkbelow)
 		{
-			sector_t *lower = P_PointInSector(check->v1->fPos() + check->Delta() / 2 + sec->SkyBoxes[sector_t::floor]->Scale);
+			sector_t *lower = P_PointInSector(check->v1->fPos() + check->Delta() / 2 + sec->GetPortalDisplacement(sector_t::floor));
 			P_RecursiveSound(lower, soundtarget, splash, soundblocks, emitter, maxdist);
 		}
 		FLinePortal *port = check->getPortal();

src/p_map.cpp

@@ -656,20 +656,21 @@ double P_GetMoveFactor(const AActor *mo, double *frictionp)
 // - 0 when intersecting
 // - -1 when outside the portal
 //
+// Note that this check is done from the 'other' side of the portal
+// so plane names seem to be inverted.
+//
 //==========================================================================
 
 static int LineIsAbove(line_t *line, AActor *actor)
 {
-	AActor *point = line->frontsector->SkyBoxes[sector_t::floor];
+	if (line->frontsector->PortalBlocksMovement(sector_t::floor)) return -1;
-	if (point == NULL) return -1;
+	return line->frontsector->GetPortalPlaneZ(sector_t::floor) >= actor->Top();
-	return point->specialf1 >= actor->Top();
 }
 
 static int LineIsBelow(line_t *line, AActor *actor)
 {
-	AActor *point = line->frontsector->SkyBoxes[sector_t::ceiling];
+	if (line->frontsector->PortalBlocksMovement(sector_t::ceiling)) return -1;
-	if (point == NULL) return -1;
+	return line->frontsector->GetPortalPlaneZ(sector_t::ceiling) <= actor->Z();
-	return point->specialf1 <= actor->Z();
 }
 
 //
@@ -762,7 +763,7 @@ bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::Chec
 				if (state == 1)
 				{
 					// the line should not block but we should set the ceilingz to the portal boundary so that we can't float up into that line.
-					double portalz = cres.line->frontsector->SkyBoxes[sector_t::floor]->specialf1;
+					double portalz = cres.line->frontsector->GetPortalPlaneZ(sector_t::floor);
 					if (portalz < tm.ceilingz)
 					{
 						tm.ceilingz = portalz;
@@ -778,7 +779,7 @@ bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::Chec
 				if (state == -1) return true;
 				if (state == 1)
 				{
-					double portalz = cres.line->frontsector->SkyBoxes[sector_t::ceiling]->specialf1;
+					double portalz = cres.line->frontsector->GetPortalPlaneZ(sector_t::ceiling);
 					if (portalz > tm.floorz)
 					{
 						tm.floorz = portalz;
@@ -3529,20 +3530,20 @@ struct aim_t
 
 	void EnterSectorPortal(int position, double frac, sector_t *entersec, DAngle newtoppitch, DAngle newbottompitch)
 	{
-		AActor *portal = entersec->SkyBoxes[position];
+		double portalz = entersec->GetPortalPlaneZ(position);
 
-		if (position == sector_t::ceiling && portal->specialf1 < limitz) return;
+		if (position == sector_t::ceiling && portalz < limitz) return;
-		else if (position == sector_t::floor && portal->specialf1 > limitz) return;
+		else if (position == sector_t::floor && portalz > limitz) return;
 		aim_t newtrace = Clone();
 
 
 		newtrace.toppitch = newtoppitch;
 		newtrace.bottompitch = newbottompitch;
 		newtrace.aimdir = position == sector_t::ceiling? aim_t::aim_up : aim_t::aim_down;
-		newtrace.startpos = startpos + portal->Scale;
+		newtrace.startpos = startpos + entersec->GetPortalDisplacement(position);
 		newtrace.startfrac = frac + 1. / attackrange;	// this is to skip the transition line to the portal which would produce a bogus opening
 		newtrace.lastsector = P_PointInSector(newtrace.startpos + aimtrace * newtrace.startfrac);
-		newtrace.limitz = portal->specialf1;
+		newtrace.limitz = portalz;
 		if (aimdebug)
 			Printf("-----Entering %s portal from sector %d to sector %d\n", position ? "ceiling" : "floor", lastsector->sectornum, newtrace.lastsector->sectornum);
 		newtrace.AimTraverse();
@@ -6253,22 +6254,22 @@ void AActor::UpdateRenderSectorList()
 		ClearRenderSectorList();
 		while (!sec->PortalBlocksMovement(sector_t::ceiling))
 		{
-			double planeh = sec->SkyBoxes[sector_t::ceiling]->specialf1;
+			double planeh = sec->GetPortalPlaneZ(sector_t::ceiling);
 			if (planeh < lasth) break;	// broken setup.
 			if (Top() + SPRITE_SPACE < planeh) break;
 			lasth = planeh;
-			DVector2 newpos = Pos() + sec->SkyBoxes[sector_t::ceiling]->Scale;
+			DVector2 newpos = Pos() + sec->GetPortalDisplacement(sector_t::ceiling);
 			sec = P_PointInSector(newpos);
 			render_sectorlist = P_AddSecnode(sec, this, render_sectorlist, sec->render_thinglist);
 		}
 		lasth = FLT_MAX;
 		while (!sec->PortalBlocksMovement(sector_t::floor))
 		{
-			double planeh = sec->SkyBoxes[sector_t::floor]->specialf1;
+			double planeh = sec->GetPortalPlaneZ(sector_t::floor);
 			if (planeh > lasth) break;	// broken setup.
 			if (Z() - SPRITE_SPACE > planeh) break;
 			lasth = planeh;
-			DVector2 newpos = Pos() + sec->SkyBoxes[sector_t::floor]->Scale;
+			DVector2 newpos = Pos() + sec->GetPortalDisplacement(sector_t::floor);
 			sec = P_PointInSector(newpos);
 			render_sectorlist = P_AddSecnode(sec, this, render_sectorlist, sec->render_thinglist);
 		}

src/p_maputl.cpp

@@ -174,7 +174,7 @@ void P_LineOpening (FLineOpening &open, AActor *actor, const line_t *linedef, co
 			{
 				// We must check through the portal for the actual dropoff.
 				// If there's no lines in the lower sections we'd never get a usable value otherwise.
-				open.lowfloor = back->NextLowestFloorAt(pos.X, pos.Y, back->SkyBoxes[sector_t::floor]->specialf1-1);
+				open.lowfloor = back->NextLowestFloorAt(pos.X, pos.Y, back->GetPortalPlaneZ(sector_t::floor) - EQUAL_EPSILON);
 			}
 		}
 		else
@@ -188,7 +188,7 @@ void P_LineOpening (FLineOpening &open, AActor *actor, const line_t *linedef, co
 			{
 				// We must check through the portal for the actual dropoff.
 				// If there's no lines in the lower sections we'd never get a usable value otherwise.
-				open.lowfloor = front->NextLowestFloorAt(pos.X, pos.Y, front->SkyBoxes[sector_t::floor]->specialf1 - 1);
+				open.lowfloor = front->NextLowestFloorAt(pos.X, pos.Y, front->GetPortalPlaneZ(sector_t::floor) - EQUAL_EPSILON);
 			}
 		}
 		open.frontfloorplane = front->floorplane;
@@ -735,7 +735,7 @@ bool FMultiBlockLinesIterator::GoUp(double x, double y)
 	{
 		if (!cursector->PortalBlocksMovement(sector_t::ceiling))
 		{
-			startIteratorForGroup(cursector->SkyBoxes[sector_t::ceiling]->Sector->PortalGroup);
+			startIteratorForGroup(cursector->GetOppositePortalGroup(sector_t::ceiling));
 			portalflags = FFCF_NOFLOOR;
 			return true;
 		}
@@ -756,7 +756,7 @@ bool FMultiBlockLinesIterator::GoDown(double x, double y)
 	{
 		if (!cursector->PortalBlocksMovement(sector_t::floor))
 		{
-			startIteratorForGroup(cursector->SkyBoxes[sector_t::floor]->Sector->PortalGroup);
+			startIteratorForGroup(cursector->GetOppositePortalGroup(sector_t::floor));
 			portalflags = FFCF_NOCEILING;
 			return true;
 		}

src/p_mobj.cpp

@@ -3169,10 +3169,9 @@ DVector3 AActor::GetPortalTransition(double byoffset, sector_t **pSec)
 
 	while (!sec->PortalBlocksMovement(sector_t::ceiling))
 	{
-		AActor *port = sec->SkyBoxes[sector_t::ceiling];
+		if (testz > sec->GetPortalPlaneZ(sector_t::ceiling))
-		if (testz > port->specialf1)
 		{
-			pos = PosRelative(port->Sector);
+			pos = PosRelative(sec->GetOppositePortalGroup(sector_t::ceiling));
 			sec = P_PointInSector(pos);
 			moved = true;
 		}
@@ -3182,10 +3181,9 @@ DVector3 AActor::GetPortalTransition(double byoffset, sector_t **pSec)
 	{
 		while (!sec->PortalBlocksMovement(sector_t::floor))
 		{
-			AActor *port = sec->SkyBoxes[sector_t::floor];
+			if (testz <= sec->GetPortalPlaneZ(sector_t::floor))
-			if (testz <= port->specialf1)
 			{
-				pos = PosRelative(port->Sector);
+				pos = PosRelative(sec->GetOppositePortalGroup(sector_t::floor));
 				sec = P_PointInSector(pos);
 			}
 			else break;
@@ -3202,12 +3200,11 @@ void AActor::CheckPortalTransition(bool islinked)
 	bool moved = false;
 	while (!Sector->PortalBlocksMovement(sector_t::ceiling))
 	{
-		AActor *port = Sector->SkyBoxes[sector_t::ceiling];
+		if (Z() > Sector->GetPortalPlaneZ(sector_t::ceiling))
-		if (Z() > port->specialf1)
 		{
 			DVector3 oldpos = Pos();
 			if (islinked && !moved) UnlinkFromWorld();
-			SetXYZ(PosRelative(port->Sector));
+			SetXYZ(PosRelative(Sector->GetOppositePortalGroup(sector_t::ceiling)));
 			Prev = Pos() - oldpos;
 			Sector = P_PointInSector(Pos());
 			PrevPortalGroup = Sector->PortalGroup;
@@ -3219,12 +3216,12 @@ void AActor::CheckPortalTransition(bool islinked)
 	{
 		while (!Sector->PortalBlocksMovement(sector_t::floor))
 		{
-			AActor *port = Sector->SkyBoxes[sector_t::floor];
+			double portalz = Sector->GetPortalPlaneZ(sector_t::floor);
-			if (Z() < port->specialf1 && floorz < port->specialf1)
+			if (Z() < portalz && floorz < portalz)
 			{
 				DVector3 oldpos = Pos();
 				if (islinked && !moved) UnlinkFromWorld();
-				SetXYZ(PosRelative(port->Sector));
+				SetXYZ(PosRelative(Sector->GetOppositePortalGroup(sector_t::floor)));
 				Prev = Pos() - oldpos;
 				Sector = P_PointInSector(Pos());
 				PrevPortalGroup = Sector->PortalGroup;

src/p_sectors.cpp

@@ -895,10 +895,10 @@ double sector_t::HighestCeilingAt(const DVector2 &p, sector_t **resultsec)
 	DVector2 pos = p;
 
 	// Continue until we find a blocking portal or a portal below where we actually are.
-	while (!check->PortalBlocksMovement(ceiling) && planeheight < check->SkyBoxes[ceiling]->specialf1)
+	while (!check->PortalBlocksMovement(ceiling) && planeheight < check->GetPortalPlaneZ(ceiling))
 	{
-		pos += check->SkyBoxes[ceiling]->Scale;
+		pos += check->GetPortalDisplacement(ceiling);
-		planeheight = check->SkyBoxes[ceiling]->specialf1;
+		planeheight = check->GetPortalPlaneZ(ceiling);
 		check = P_PointInSector(pos);
 	}
 	if (resultsec) *resultsec = check;
@@ -918,10 +918,10 @@ double sector_t::LowestFloorAt(const DVector2 &p, sector_t **resultsec)
 	DVector2 pos = p;
 
 	// Continue until we find a blocking portal or a portal above where we actually are.
-	while (!check->PortalBlocksMovement(floor) && planeheight > check->SkyBoxes[floor]->specialf1)
+	while (!check->PortalBlocksMovement(floor) && planeheight > check->GetPortalPlaneZ(floor))
 	{
-		pos += check->SkyBoxes[floor]->Scale;
+		pos += check->GetPortalDisplacement(floor);
-		planeheight = check->SkyBoxes[floor]->specialf1;
+		planeheight = check->GetPortalPlaneZ(ceiling);
 		check = P_PointInSector(pos);
 	}
 	if (resultsec) *resultsec = check;
@@ -956,7 +956,7 @@ double sector_t::NextHighestCeilingAt(double x, double y, double bottomz, double
 				return ff_bottom;
 			}
 		}
-		if ((flags & FFCF_NOPORTALS) || sec->PortalBlocksMovement(ceiling) || planeheight >= sec->SkyBoxes[ceiling]->specialf1)
+		if ((flags & FFCF_NOPORTALS) || sec->PortalBlocksMovement(ceiling) || planeheight >= sec->GetPortalPlaneZ(ceiling))
 		{ // Use sector's floor
 			if (resultffloor) *resultffloor = NULL;
 			if (resultsec) *resultsec = sec;
@@ -964,10 +964,10 @@ double sector_t::NextHighestCeilingAt(double x, double y, double bottomz, double
 		}
 		else
 		{
-			DVector2 pos = sec->SkyBoxes[ceiling]->Scale;
+			DVector2 pos = sec->GetPortalDisplacement(ceiling);
 			x += pos.X;
 			y += pos.Y;
-			planeheight = sec->SkyBoxes[ceiling]->specialf1;
+			planeheight = sec->GetPortalPlaneZ(ceiling);
 			sec = P_PointInSector(x, y);
 		}
 	}
@@ -1001,7 +1001,7 @@ double sector_t::NextLowestFloorAt(double x, double y, double z, int flags, doub
 				}
 			}
 		}
-		if ((flags & FFCF_NOPORTALS) || sec->PortalBlocksMovement(sector_t::floor) || planeheight <= sec->SkyBoxes[floor]->specialf1)
+		if ((flags & FFCF_NOPORTALS) || sec->PortalBlocksMovement(sector_t::floor) || planeheight <= sec->GetPortalPlaneZ(floor))
 		{ // Use sector's floor
 			if (resultffloor) *resultffloor = NULL;
 			if (resultsec) *resultsec = sec;
@@ -1009,10 +1009,10 @@ double sector_t::NextLowestFloorAt(double x, double y, double z, int flags, doub
 		}
 		else
 		{
-			DVector2 pos = sec->SkyBoxes[floor]->Scale;
+			DVector2 pos = sec->GetPortalDisplacement(floor);
 			x += pos.X;
 			y += pos.Y;
-			planeheight = sec->SkyBoxes[floor]->specialf1;
+			planeheight = sec->GetPortalPlaneZ(floor);
 			sec = P_PointInSector(x, y);
 		}
 	}

src/p_sight.cpp

@@ -254,11 +254,11 @@ bool SightCheck::PTR_SightTraverse (intercept_t *in)
 
 		if (portaldir != sector_t::floor && (open.portalflags & SO_TOPBACK) && !(open.portalflags & SO_TOPFRONT))
 		{
-			portals.Push({ in->frac, topslope, bottomslope, sector_t::ceiling, backsec->SkyBoxes[sector_t::ceiling]->Sector->PortalGroup });
+			portals.Push({ in->frac, topslope, bottomslope, sector_t::ceiling, backsec->GetOppositePortalGroup(sector_t::ceiling) });
 		}
 		if (portaldir != sector_t::ceiling && (open.portalflags & SO_BOTTOMBACK) && !(open.portalflags & SO_BOTTOMFRONT))
 		{
-			portals.Push({ in->frac, topslope, bottomslope, sector_t::floor, backsec->SkyBoxes[sector_t::floor]->Sector->PortalGroup });
+			portals.Push({ in->frac, topslope, bottomslope, sector_t::floor, backsec->GetOppositePortalGroup(sector_t::floor) });
 		}
 	}
 	if (lport)
@@ -628,11 +628,11 @@ bool SightCheck::P_SightPathTraverse ()
 	// We also must check if the starting sector contains  portals, and start sight checks in those as well.
 	if (portaldir != sector_t::floor && checkceiling && !lastsector->PortalBlocksSight(sector_t::ceiling))
 	{
-		portals.Push({ 0, topslope, bottomslope, sector_t::ceiling, lastsector->SkyBoxes[sector_t::ceiling]->Sector->PortalGroup });
+		portals.Push({ 0, topslope, bottomslope, sector_t::ceiling, lastsector->GetOppositePortalGroup(sector_t::ceiling) });
 	}
 	if (portaldir != sector_t::ceiling && checkfloor && !lastsector->PortalBlocksSight(sector_t::floor))
 	{
-		portals.Push({ 0, topslope, bottomslope, sector_t::floor, lastsector->SkyBoxes[sector_t::floor]->Sector->PortalGroup });
+		portals.Push({ 0, topslope, bottomslope, sector_t::floor, lastsector->GetOppositePortalGroup(sector_t::floor) });
 	}
 
 	x1 -= bmaporgx;

src/p_trace.cpp

@@ -112,10 +112,9 @@ static void GetPortalTransition(DVector3 &pos, sector_t *&sec)
 
 	while (!sec->PortalBlocksMovement(sector_t::ceiling))
 	{
-		AActor *port = sec->SkyBoxes[sector_t::ceiling];
+		if (pos.Z > sec->GetPortalPlaneZ(sector_t::ceiling))
-		if (pos.Z > port->specialf1)
 		{
-			pos += port->Scale;
+			pos += sec->GetPortalDisplacement(sector_t::ceiling);
 			sec = P_PointInSector(pos);
 			moved = true;
 		}
@@ -125,10 +124,9 @@ static void GetPortalTransition(DVector3 &pos, sector_t *&sec)
 	{
 		while (!sec->PortalBlocksMovement(sector_t::floor))
 		{
-			AActor *port = sec->SkyBoxes[sector_t::floor];
+			if (pos.Z <= sec->GetPortalPlaneZ(sector_t::floor))
-			if (pos.Z <= port->specialf1)
 			{
-				pos += port->Scale;
+				pos += sec->GetPortalDisplacement(sector_t::floor);
 				sec = P_PointInSector(pos);
 			}
 			else break;
@@ -208,18 +206,17 @@ bool Trace(const DVector3 &start, sector_t *sector, const DVector3 &direction, d
 
 void FTraceInfo::EnterSectorPortal(FPathTraverse &pt, int position, double frac, sector_t *entersec)
 {
-	AActor *portal = entersec->SkyBoxes[position];
+	DVector2 displacement = entersec->GetPortalDisplacement(position);;
-
 	double enterdist = MaxDist * frac;
 	DVector3 exit = Start + enterdist * Vec;
-	DVector3 enter = exit + portal->Scale;
+	DVector3 enter = exit + displacement;
 
-	Start += portal->Scale;
+	Start += displacement;
 	CurSector = P_PointInSector(enter);
 	inshootthrough = true;
 	startfrac = frac;
 	EnterDist = enterdist;
-	pt.PortalRelocate(portal, ptflags, frac);
+	pt.PortalRelocate(entersec->SkyBoxes[position], ptflags, frac);
 
 	if ((TraceFlags & TRACE_ReportPortals) && TraceCallback != NULL)
 	{
@@ -763,7 +760,7 @@ bool FTraceInfo::TraceTraverse (int ptflags)
 		if (Vec.Z < 0 && !CurSector->PortalBlocksMovement(sector_t::floor))
 		{
 			// calculate position where the portal is crossed
-			double portz = CurSector->SkyBoxes[sector_t::floor]->specialf1;
+			double portz = CurSector->GetPortalPlaneZ(sector_t::floor);
 			if (hit.Z < portz && limitz > portz)
 			{
 				limitz = portz;
@@ -775,7 +772,7 @@ bool FTraceInfo::TraceTraverse (int ptflags)
 		else if (Vec.Z > 0 && !CurSector->PortalBlocksMovement(sector_t::ceiling))
 		{
 			// calculate position where the portal is crossed
-			double portz = CurSector->SkyBoxes[sector_t::ceiling]->specialf1;
+			double portz = CurSector->GetPortalPlaneZ(sector_t::ceiling);
 			if (hit.Z > portz && limitz < portz)
 			{
 				limitz = portz;

src/portal.cpp

@@ -1050,8 +1050,8 @@ void P_CreateLinkedPortals()
 		}
 		if (sectors[i].PortalIsLinked(sector_t::ceiling) && sectors[i].PortalIsLinked(sector_t::floor))
 		{
-			double cz = sectors[i].SkyBoxes[sector_t::ceiling]->specialf1;
+			double cz = sectors[i].GetPortalPlaneZ(sector_t::ceiling);
-			double fz = sectors[i].SkyBoxes[sector_t::floor]->specialf1;
+			double fz = sectors[i].GetPortalPlaneZ(sector_t::floor);
 			if (cz < fz)
 			{
 				// This is a fatal condition. We have to remove one of the two portals. Choose the one that doesn't match the current plane
@@ -1162,22 +1162,22 @@ bool P_CollectConnectedGroups(int startgroup, const DVector3 &position, double u
 	{
 		sector_t *sec = P_PointInSector(position);
 		sector_t *wsec = sec;
-		while (!wsec->PortalBlocksMovement(sector_t::ceiling) && upperz > wsec->SkyBoxes[sector_t::ceiling]->specialf1)
+		while (!wsec->PortalBlocksMovement(sector_t::ceiling) && upperz > wsec->GetPortalPlaneZ(sector_t::ceiling))
 		{
-			sector_t *othersec = wsec->SkyBoxes[sector_t::ceiling]->Sector;
+			int othergroup = wsec->GetOppositePortalGroup(sector_t::ceiling);
-			DVector2 pos = Displacements.getOffset(startgroup, othersec->PortalGroup) + position;
+			DVector2 pos = Displacements.getOffset(startgroup, othergroup) + position;
-			processMask.setBit(othersec->PortalGroup);
+			processMask.setBit(othergroup);
-			out.Add(othersec->PortalGroup | FPortalGroupArray::UPPER);
+			out.Add(othergroup | FPortalGroupArray::UPPER);
 			wsec = P_PointInSector(pos);	// get upper sector at the exact spot we want to check and repeat
 			retval = true;
 		}
 		wsec = sec;
-		while (!wsec->PortalBlocksMovement(sector_t::floor) && position.Z < wsec->SkyBoxes[sector_t::floor]->specialf1)
+		while (!wsec->PortalBlocksMovement(sector_t::floor) && position.Z < wsec->GetPortalPlaneZ(sector_t::floor))
 		{
-			sector_t *othersec = wsec->SkyBoxes[sector_t::floor]->Sector;
+			int othergroup = wsec->GetOppositePortalGroup(sector_t::floor);
-			DVector2 pos = Displacements.getOffset(startgroup, othersec->PortalGroup) + position;
+			DVector2 pos = Displacements.getOffset(startgroup, othergroup) + position;
-			processMask.setBit(othersec->PortalGroup | FPortalGroupArray::LOWER);
+			processMask.setBit(othergroup | FPortalGroupArray::LOWER);
-			out.Add(othersec->PortalGroup);
+			out.Add(othergroup);
 			wsec = P_PointInSector(pos);	// get lower sector at the exact spot we want to check and repeat
 			retval = true;
 		}
@@ -1204,9 +1204,9 @@ bool P_CollectConnectedGroups(int startgroup, const DVector3 &position, double u
 							sector_t *sec = s ? ld->backsector : ld->frontsector;
 							if (sec && !(sec->PortalBlocksMovement(sector_t::ceiling)))
 							{
-								if (sec->SkyBoxes[sector_t::ceiling]->specialf1 < upperz)
+								if (sec->GetPortalPlaneZ(sector_t::ceiling) < upperz)
 								{
-									int grp = sec->SkyBoxes[sector_t::ceiling]->Sector->PortalGroup;
+									int grp = sec->GetOppositePortalGroup(sector_t::ceiling);
 									if (!(processMask.getBit(grp)))
 									{
 										processMask.setBit(grp);
@@ -1223,9 +1223,9 @@ bool P_CollectConnectedGroups(int startgroup, const DVector3 &position, double u
 							sector_t *sec = s ? ld->backsector : ld->frontsector;
 							if (sec && !(sec->PortalBlocksMovement(sector_t::floor)))
 							{
-								if (sec->SkyBoxes[sector_t::floor]->specialf1 > position.Z)
+								if (sec->GetPortalPlaneZ(sector_t::floor) > position.Z)
 								{
-									int grp = sec->SkyBoxes[sector_t::floor]->Sector->PortalGroup;
+									int grp = sec->GetOppositePortalGroup(sector_t::floor);
 									if (!(processMask.getBit(grp)))
 									{
 										processMask.setBit(grp);

src/r_defs.h

@@ -931,7 +931,7 @@ public:
 	bool PortalBlocksView(int plane)
 	{
 		if (SkyBoxes[plane] == NULL) return true;
-		if (SkyBoxes[plane]->special1 != SKYBOX_LINKEDPORTAL) return false;
+		if (GetPortalType(plane) != SKYBOX_LINKEDPORTAL) return false;
 		return !!(planes[plane].Flags & (PLANEF_NORENDER | PLANEF_DISABLED | PLANEF_OBSTRUCTED));
 	}
 
@@ -952,7 +952,28 @@ public:
 
 	bool PortalIsLinked(int plane)
 	{
-		return (SkyBoxes[plane] != NULL && SkyBoxes[plane]->special1 == SKYBOX_LINKEDPORTAL);
+		return (SkyBoxes[plane] != NULL && GetPortalType(plane) == SKYBOX_LINKEDPORTAL);
+	}
+
+	// These intentionally do not validate the SkyBoxes pointers.
+	double GetPortalPlaneZ(int plane)
+	{
+		return SkyBoxes[plane]->specialf1;
+	}
+
+	DVector2 GetPortalDisplacement(int plane)
+	{
+		return SkyBoxes[plane]->Scale;
+	}
+
+	int GetPortalType(int plane)
+	{
+		return SkyBoxes[plane]->special1;
+	}
+
+	int GetOppositePortalGroup(int plane)
+	{
+		return SkyBoxes[plane]->Sector->PortalGroup;
 	}
 
 	int GetTerrain(int pos) const;

src/r_utility.cpp

@@ -694,10 +694,9 @@ void R_InterpolateView (player_t *player, double Frac, InterpolationViewer *ivie
 	bool moved = false;
 	while (!viewsector->PortalBlocksMovement(sector_t::ceiling))
 	{
-		AActor *point = viewsector->SkyBoxes[sector_t::ceiling];
+		if (ViewPos.Z > viewsector->GetPortalPlaneZ(sector_t::ceiling))
-		if (ViewPos.Z > point->specialf1)
 		{
-			ViewPos += point->Scale;
+			ViewPos += viewsector->GetPortalDisplacement(sector_t::ceiling);
 			viewsector = R_PointInSubsector(ViewPos)->sector;
 			moved = true;
 		}
@@ -707,10 +706,9 @@ void R_InterpolateView (player_t *player, double Frac, InterpolationViewer *ivie
 	{
 		while (!viewsector->PortalBlocksMovement(sector_t::floor))
 		{
-			AActor *point = viewsector->SkyBoxes[sector_t::floor];
+			if (ViewPos.Z < viewsector->GetPortalPlaneZ(sector_t::floor))
-			if (ViewPos.Z < point->specialf1)
 			{
-				ViewPos += point->Scale;
+				ViewPos += viewsector->GetPortalDisplacement(sector_t::floor);
 				viewsector = R_PointInSubsector(ViewPos)->sector;
 				moved = true;
 			}