diff --git a/src/level/doomdata.h b/src/level/doomdata.h
index 693ed5e..849a709 100644
--- a/src/level/doomdata.h
+++ b/src/level/doomdata.h
@@ -153,11 +153,23 @@ struct IntSector
 		struct { bool skyFloor, skyCeiling; };
 	};
 
-	inline const char* GetTextureName(int plane) const { return plane != PLANE_FLOOR ? data.ceilingpic : data.floorpic; }
-
 	TArray<UDMFKey> props;
 
 	TArray<IntLineDef*> lines;
+
+	// Utility functions
+	inline const char* GetTextureName(int plane) const { return plane != PLANE_FLOOR ? data.ceilingpic : data.floorpic; }
+
+	inline bool HasTag(int sectorTag) const
+	{
+		if (tags.Size() <= 0 && sectorTag == 0)
+			return true;
+		for (auto tag : tags)
+		{
+			if (tag == sectorTag) return true;
+		}
+		return false;
+	}
 };
 
 struct MapSubsector
diff --git a/src/lightmap/gpuraytracer.cpp b/src/lightmap/gpuraytracer.cpp
index 03567c0..21dc2dd 100644
--- a/src/lightmap/gpuraytracer.cpp
+++ b/src/lightmap/gpuraytracer.cpp
@@ -1015,7 +1015,7 @@ std::vector<PortalInfo> GPURaytracer::CreatePortalInfo()
 
 	for (const auto& surface : mesh->surfaces)
 	{
-		if (surface->portalDestinationIndex >= 0)
+		if (surface->portalIndex >= 0)
 		{
 			PortalInfo info;
 			info.Transformation = mesh->portals[surface->portalIndex]->transformation;
diff --git a/src/lightmap/levelmesh.cpp b/src/lightmap/levelmesh.cpp
index bcdeb89..48573c0 100644
--- a/src/lightmap/levelmesh.cpp
+++ b/src/lightmap/levelmesh.cpp
@@ -510,6 +510,92 @@ int LevelMesh::CreateLinePortal(FLevel& doomMap, const IntLineDef& srcLine, cons
 	return int(portals.size() - 1);
 }
 
+int LevelMesh::CheckAndMakePortal(FLevel& doomMap, MapSubsectorEx* sub, IntSector* sector, int typeIndex, int plane)
+{
+	const auto& lines = doomMap.GetSectorFromSubSector(sub)->lines;
+
+	for (const auto& line : lines)
+	{
+		if (line->special == Sector_SetPortal && line->args[0] && line->args[2] == plane && !line->args[3] && sector->HasTag(line->args[0]))
+		{
+			const IntLineDef* dstLine = nullptr;
+
+			// Find the other portal line
+			for (const auto &targetLine : doomMap.Lines)
+			{
+				if (targetLine.special == Sector_SetPortal && targetLine.args[2] == plane && targetLine.args[3] && line->args[0] == targetLine.args[0])
+				{
+					dstLine = &targetLine;
+					break;
+				}
+			}
+
+			if (dstLine)
+			{
+				 return CreatePlanePortal(doomMap, *line, *dstLine);
+			}
+		}
+	}
+
+	return -1;
+}
+
+int LevelMesh::CreatePlanePortal(FLevel& doomMap, const IntLineDef& srcLine, const IntLineDef& dstLine)
+{
+	auto portal = std::make_unique<Portal>();
+
+	// Calculate portal transformation
+	{
+		FloatVertex srcV1 = doomMap.GetSegVertex(srcLine.v1);
+		FloatVertex srcV2 = doomMap.GetSegVertex(srcLine.v2);
+		FloatVertex dstV1 = doomMap.GetSegVertex(dstLine.v1);
+		FloatVertex dstV2 = doomMap.GetSegVertex(dstLine.v2);
+
+		int alignment = srcLine.args[2];
+
+		double srcAZ = 0;
+		double srcBZ = 0;
+		double dstAZ = 0;
+		double dstBZ = 0;
+
+		const auto* srcFront = srcLine.frontsector;
+		const auto* dstFront = dstLine.frontsector;
+
+		if (alignment == 0) // floor
+		{
+			srcAZ = srcFront->floorplane.zAt(srcV1.x, srcV1.y);
+			srcBZ = srcFront->floorplane.zAt(srcV2.x, srcV2.y);
+			dstAZ = dstFront->ceilingplane.zAt(dstV1.x, dstV1.y);
+			dstBZ = dstFront->ceilingplane.zAt(dstV2.x, dstV2.y);
+		}
+		else // ceiling
+		{
+			srcAZ = srcFront->ceilingplane.zAt(srcV1.x, srcV1.y);
+			srcBZ = srcFront->ceilingplane.zAt(srcV2.x, srcV2.y);
+			dstAZ = dstFront->floorplane.zAt(dstV1.x, dstV1.y);
+			dstBZ = dstFront->floorplane.zAt(dstV2.x, dstV2.y);
+		}
+
+		const vec3 vecSrcA = vec3(vec2(srcV1.x, srcV1.y), srcAZ);
+		const vec3 vecSrcB = vec3(vec2(srcV2.x, srcV2.y), srcAZ);
+		const vec3 vecDstA = vec3(vec2(dstV1.x, dstV1.y), dstAZ);
+		const vec3 vecDstB = vec3(vec2(dstV2.x, dstV2.y), dstBZ);
+
+		// Translation
+		vec3 originSrc = (vecSrcB + vecSrcA) * 0.5f;
+		vec3 originDst = (vecDstB + vecDstA) * 0.5f;
+
+		vec3 translation = originDst - originSrc;
+
+		// printf("Portal translation: %.3f %.3f %.3f\n", translation.x, translation.y, translation.z);
+
+		portal->transformation = mat4::translate(translation);
+	}
+
+	portals.push_back(std::move(portal));
+	return int(portals.size() - 1);
+}
+
 void LevelMesh::CreateSideSurfaces(FLevel &doomMap, IntSideDef *side)
 {
 	IntSector *front;
@@ -585,6 +671,8 @@ void LevelMesh::CreateSideSurfaces(FLevel &doomMap, IntSideDef *side)
 			surf->portalDestinationIndex = destLineIndex;
 
 			surf->portalIndex = CreateLinePortal(doomMap, *side->line, doomMap.Lines[destLineIndex]);
+
+			surfaces.push_back(std::move(surf));
 			return;
 		}
 		else
@@ -874,6 +962,7 @@ void LevelMesh::CreateFloorSurface(FLevel &doomMap, MapSubsectorEx *sub, IntSect
 	if (!is3DFloor)
 	{
 		surf->plane = sector->floorplane;
+		surf->portalIndex = CheckAndMakePortal(doomMap, sub, sector, typeIndex, PLANE_FLOOR);
 	}
 	else
 	{
@@ -912,6 +1001,7 @@ void LevelMesh::CreateCeilingSurface(FLevel &doomMap, MapSubsectorEx *sub, IntSe
 	if (!is3DFloor)
 	{
 		surf->plane = sector->ceilingplane;
+		surf->portalIndex = CheckAndMakePortal(doomMap, sub, sector, typeIndex, PLANE_CEILING);
 	}
 	else
 	{
diff --git a/src/lightmap/levelmesh.h b/src/lightmap/levelmesh.h
index 3834a07..63fb0d2 100644
--- a/src/lightmap/levelmesh.h
+++ b/src/lightmap/levelmesh.h
@@ -160,5 +160,8 @@ private:
 
 	static bool IsDegenerate(const vec3 &v0, const vec3 &v1, const vec3 &v2);
 
+	int CheckAndMakePortal(FLevel& doomMap, MapSubsectorEx* sub, IntSector* sector, int typeIndex, int plane);
+
 	int CreateLinePortal(FLevel &doomMap, const IntLineDef& srcLine, const IntLineDef& dstLine);
+	int CreatePlanePortal(FLevel &doomMap, const IntLineDef& srcLine, const IntLineDef& dstLine);
 };