diff --git a/source/core/rendering/hw_entrypoint.cpp b/source/core/rendering/hw_entrypoint.cpp
index b38dfecca..f41a25754 100644
--- a/source/core/rendering/hw_entrypoint.cpp
+++ b/source/core/rendering/hw_entrypoint.cpp
@@ -381,9 +381,7 @@ FSerializer& Serialize(FSerializer& arc, const char* key, PortalDesc& obj, Porta
 	if (arc.BeginObject(key))
 	{
 		arc("type", obj.type)
-			("dx", obj.dx)
-			("dy", obj.dy)
-			("dz", obj.dz)
+			("d", obj.delta)
 			("targets", obj.targets)
 			.EndObject();
 	}
diff --git a/source/core/rendering/hw_sections.cpp b/source/core/rendering/hw_sections.cpp
index 6465dd020..72ca158b8 100644
--- a/source/core/rendering/hw_sections.cpp
+++ b/source/core/rendering/hw_sections.cpp
@@ -42,6 +42,7 @@
 #include "hw_sections.h"
 #include "memarena.h"
 #include "c_cvars.h"
+#include "gamefuncs.h"
 
 void CreateVertexMap();
 
diff --git a/source/core/rendering/render.h b/source/core/rendering/render.h
index 4270164a2..ba43b0b16 100644
--- a/source/core/rendering/render.h
+++ b/source/core/rendering/render.h
@@ -11,7 +11,7 @@ void render_camtex(DCoreActor* playersprite, const DVector3& position, sectortyp
 struct PortalDesc
 {
 	int type;
-	int dx, dy, dz;
+	DVector3 delta;
 	TArray<int> targets;
 };
 
@@ -30,9 +30,7 @@ inline int portalAdd(int type, int target, const DVector3& offset)
 	auto& pt = allPortals[allPortals.Reserve(1)];
 	pt.type = type;
 	if (target >= 0) pt.targets.Push(target);
-	pt.dx = offset.X * worldtoint;
-	pt.dy = offset.Y * worldtoint;
-	pt.dz = offset.Z * zworldtoint;
+	pt.delta = offset;
 	return allPortals.Size() - 1;
 }
 
@@ -52,7 +50,7 @@ inline void mergePortals()
 				for (unsigned j = i + 1; j < allPortals.Size(); j++)
 				{
 					auto& pt2 = allPortals[j];
-					if (pt1.type != pt2.type || pt1.dx != pt2.dx || pt1.dy != pt2.dy || pt1.dz != pt2.dz) continue;
+					if (pt1.type != pt2.type || pt1.delta != pt2.delta) continue;
 					for (unsigned s = 0; s < pt1.targets.Size() && pt2.targets.Size(); s++)
 					{
 						for (unsigned t = 0; t < pt2.targets.Size(); t++)
diff --git a/source/core/rendering/scene/hw_portal.cpp b/source/core/rendering/scene/hw_portal.cpp
index b4483d664..83129beb1 100644
--- a/source/core/rendering/scene/hw_portal.cpp
+++ b/source/core/rendering/scene/hw_portal.cpp
@@ -796,7 +796,7 @@ bool HWSectorStackPortal::Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *c
 	auto portal = origin;
 	auto &vp = di->Viewpoint;
 
-	vp.Pos += DVector3(portal->dx / 16., portal->dy / -16., portal->dz / -256.);
+	vp.Pos += DVector3(portal->delta.X, -portal->delta.Y, -portal->delta.Z);
 	vp.SectNums = portal->targets.Data();
 	vp.SectCount = portal->targets.Size();
 	type = origin->type;
diff --git a/source/games/duke/src/premap.cpp b/source/games/duke/src/premap.cpp
index 6ef174016..66aca1671 100644
--- a/source/games/duke/src/premap.cpp
+++ b/source/games/duke/src/premap.cpp
@@ -855,12 +855,13 @@ static void SpawnPortals()
 	{
 		if (act->spr.picnum == SECTOREFFECTOR && act->spr.lotag == tag)
 		{
-			if (processedTags.Find(act->spr.hitag) == processedTags.Size())
+			int hitag = act->spr.hitag;
+			if (processedTags.Find(hitag) == processedTags.Size())
 			{
 				DukeStatIterator it2(STAT_RAROR);
 				while (auto act2 = it2.Next())
 				{
-					if (act2->spr.picnum == SECTOREFFECTOR && act2->spr.lotag == tag + 1 && act2->spr.hitag == act->spr.hitag)
+					if (act2->spr.picnum == SECTOREFFECTOR && act2->spr.lotag == tag + 1 && act2->spr.hitag == hitag)
 					{
 						if (processedTags.Find(act->spr.hitag) == processedTags.Size())
 						{
@@ -868,15 +869,15 @@ static void SpawnPortals()
 							s1->portalflags = PORTAL_SECTOR_FLOOR;
 							s2->portalflags = PORTAL_SECTOR_CEILING;
 							DVector2 diff = act->spr.pos.XY() - act2->spr.pos.XY();
-							s1->portalnum = portalAdd(PORTAL_SECTOR_FLOOR, sectnum(s2), DVector3(-diff, act->spr.hitag * zmaptoworld));
-							s2->portalnum = portalAdd(PORTAL_SECTOR_CEILING, sectnum(s1), DVector3(diff, act->spr.hitag * zmaptoworld));
+							s1->portalnum = portalAdd(PORTAL_SECTOR_FLOOR, sectnum(s2), DVector3(-diff, hitag)); // uses delta.Z as temporary storage, not a real coordinate.
+							s2->portalnum = portalAdd(PORTAL_SECTOR_CEILING, sectnum(s1), DVector3(diff, hitag));
 							processedTags.Push(act->spr.hitag);
 						}
 						else
 						{
 							for (auto& p : allPortals)
 							{
-								if (p.type == PORTAL_SECTOR_FLOOR && p.dz == act->spr.hitag)
+								if (p.type == PORTAL_SECTOR_FLOOR && p.delta.Z == hitag)
 								{
 									p.targets.Push(act2->sectno());
 								}
@@ -889,7 +890,7 @@ static void SpawnPortals()
 			{
 				for (auto& p : allPortals)
 				{
-					if (p.type == PORTAL_SECTOR_CEILING && p.dz == act->spr.hitag)
+					if (p.type == PORTAL_SECTOR_CEILING && p.delta.Z == hitag)
 					{
 						p.targets.Push(act->sectno());
 					}
@@ -942,7 +943,8 @@ static void SpawnPortals()
 		}
 	nexti:;
 	}
-	for (auto& p : allPortals) p.dz = 0;
+	// clean out the tags we stored in delta.Z
+	for (auto& p : allPortals) p.delta.Z = 0;
 	mergePortals();
 }