- fixed rendering of one-sided line portals in the hardware renderer

# draw upper and lower textures when the back sector does not properly match
# do not draw middle textures on portal lines
# minor optimization to 'is***Portal' functions to avoid memory access in the most common case of no portal being present.

src/g_levellocals.h

@@ -801,19 +801,19 @@ inline FLevelLocals *line_t::GetLevel() const
 }
 inline FLinePortal *line_t::getPortal() const
 {
-	return portalindex >= GetLevel()->linePortals.Size() ? (FLinePortal*)nullptr : &GetLevel()->linePortals[portalindex];
+	return portalindex == UINT_MAX && portalindex >= GetLevel()->linePortals.Size() ? (FLinePortal*)nullptr : &GetLevel()->linePortals[portalindex];
 }
 
 // returns true if the portal is crossable by actors
 inline bool line_t::isLinePortal() const
 {
-	return portalindex >= GetLevel()->linePortals.Size() ? false : !!(GetLevel()->linePortals[portalindex].mFlags & PORTF_PASSABLE);
+	return portalindex == UINT_MAX && portalindex >= GetLevel()->linePortals.Size() ? false : !!(GetLevel()->linePortals[portalindex].mFlags & PORTF_PASSABLE);
 }
 
 // returns true if the portal needs to be handled by the renderer
 inline bool line_t::isVisualPortal() const
 {
-	return portalindex >= GetLevel()->linePortals.Size() ? false : !!(GetLevel()->linePortals[portalindex].mFlags & PORTF_VISIBLE);
+	return portalindex == UINT_MAX && portalindex >= GetLevel()->linePortals.Size() ? false : !!(GetLevel()->linePortals[portalindex].mFlags & PORTF_VISIBLE);
 }
 
 inline line_t *line_t::getPortalDestination() const

src/rendering/hwrenderer/scene/hw_bsp.cpp

@@ -142,15 +142,21 @@ void HWDrawInfo::WorkerThread()
 
 			front = hw_FakeFlat(job->sub->sector, in_area, false);
 			auto seg = job->seg;
-			if (seg->backsector)
+			auto backsector = seg->backsector;
+			if (!backsector && seg->linedef->isVisualPortal() && seg->sidedef == seg->linedef->sidedef[0]) // For one-sided portals use the portal's destination sector as backsector.
 			{
-				if (front->sectornum == seg->backsector->sectornum || (seg->sidedef->Flags & WALLF_POLYOBJ))
+				auto portal = seg->linedef->getPortal();
+				backsector = portal->mDestination->frontsector;
+			}
+			if (backsector)
+			{
+				if (front->sectornum == backsector->sectornum || ((seg->sidedef->Flags & WALLF_POLYOBJ) && !seg->linedef->isVisualPortal()))
 				{
 					back = front;
 				}
 				else
 				{
-					back = hw_FakeFlat(seg->backsector, in_area, true);
+					back = hw_FakeFlat(backsector, in_area, true);
 				}
 			}
 			else back = nullptr;

src/rendering/hwrenderer/scene/hw_walls.cpp

@@ -2046,14 +2046,16 @@ void HWWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 		return;
 	}
 
+	bool isportal = seg->linedef->isVisualPortal() && seg->sidedef == seg->linedef->sidedef[0];
+
 	//return;
 	// [GZ] 3D middle textures are necessarily two-sided, even if they lack the explicit two-sided flag
-	if (!backsector || !(seg->linedef->flags&(ML_TWOSIDED | ML_3DMIDTEX))) // one sided
+	if (!backsector || (!(seg->linedef->flags&(ML_TWOSIDED | ML_3DMIDTEX)) && !isportal)) // one sided
 	{
 		// sector's sky
 		SkyNormal(di, frontsector, v1, v2);
 
-		if (seg->linedef->isVisualPortal())
+		if (isportal)
 		{
 			lineportal = seg->linedef->getPortal()->mGroup;
 			ztop[0] = zceil[0];
@@ -2139,7 +2141,6 @@ void HWWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 
 
 		/* mid texture */
-		bool isportal = seg->linedef->isVisualPortal() && seg->sidedef == seg->linedef->sidedef[0];
 		sector_t *backsec = isportal? seg->linedef->getPortalDestination()->frontsector : backsector;
 
 		bool drawfogboundary = !di->isFullbrightScene() && di->CheckFog(frontsector, backsec);
@@ -2156,12 +2157,6 @@ void HWWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 		}
 		else texture = nullptr;
 
-		if (texture || drawfogboundary)
-		{
-			DoMidTexture(di, seg, drawfogboundary, frontsector, backsector, realfront, realback,
-				fch1, fch2, ffh1, ffh2, bch1, bch2, bfh1, bfh2);
-		}
-
 		if (isportal)
 		{
 			lineportal = seg->linedef->getPortal()->mGroup;
@@ -2171,9 +2166,18 @@ void HWWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 			zbottom[1] = bfh2;
 			PutPortal(di, PORTALTYPE_LINETOLINE, -1);
 		}
-		else if (backsector->e->XFloor.ffloors.Size() || frontsector->e->XFloor.ffloors.Size())
+		else
 		{
-			DoFFloorBlocks(di, seg, frontsector, backsector, fch1, fch2, ffh1, ffh2, bch1, bch2, bfh1, bfh2);
+			if (texture || drawfogboundary)
+			{
+				DoMidTexture(di, seg, drawfogboundary, frontsector, backsector, realfront, realback,
+					fch1, fch2, ffh1, ffh2, bch1, bch2, bfh1, bfh2);
+			}
+
+			if (backsector->e->XFloor.ffloors.Size() || frontsector->e->XFloor.ffloors.Size())
+			{
+				DoFFloorBlocks(di, seg, frontsector, backsector, fch1, fch2, ffh1, ffh2, bch1, bch2, bfh1, bfh2);
+			}
 		}
 
 		/* bottom texture */