diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4e2ffed32..3ba350529 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -885,6 +885,7 @@ set (PCH_SOURCES
 	rendering/hwrenderer/scene/hw_lighting.cpp
 	rendering/hwrenderer/scene/hw_drawlistadd.cpp
 	rendering/hwrenderer/scene/hw_setcolor.cpp
+	rendering/hwrenderer/scene/hw_meshcache.cpp
 	maploader/edata.cpp
 	maploader/specials.cpp
 	maploader/maploader.cpp
diff --git a/src/rendering/hwrenderer/hw_entrypoint.cpp b/src/rendering/hwrenderer/hw_entrypoint.cpp
index c8d4bb0fd..4bfb59407 100644
--- a/src/rendering/hwrenderer/hw_entrypoint.cpp
+++ b/src/rendering/hwrenderer/hw_entrypoint.cpp
@@ -50,6 +50,7 @@
 #include "hwrenderer/scene/hw_fakeflat.h"
 #include "hwrenderer/scene/hw_clipper.h"
 #include "hwrenderer/scene/hw_portal.h"
+#include "hwrenderer/scene/hw_meshcache.h"
 #include "hw_vrmodes.h"
 
 EXTERN_CVAR(Bool, cl_capfps)
@@ -127,6 +128,8 @@ sector_t* RenderViewpoint(FRenderViewpoint& mainvp, AActor* camera, IntRect* bou
 
 	screen->SetLevelMesh(camera->Level->levelMesh);
 
+	meshcache.Update(mainvp);
+
 	// Update the attenuation flag of all light defaults for each viewpoint.
 	// This function will only do something if the setting differs.
 	FLightDefaults::SetAttenuationForLevel(!!(camera->Level->flags3 & LEVEL3_ATTENUATE));
diff --git a/src/rendering/hwrenderer/scene/hw_drawinfo.h b/src/rendering/hwrenderer/scene/hw_drawinfo.h
index f750a2313..abbd181a1 100644
--- a/src/rendering/hwrenderer/scene/hw_drawinfo.h
+++ b/src/rendering/hwrenderer/scene/hw_drawinfo.h
@@ -182,6 +182,8 @@ struct HWDrawInfo
 	fixed_t viewx, viewy;	// since the nodes are still fixed point, keeping the view position  also fixed point for node traversal is faster.
 	bool multithread;
 
+	bool MeshBuilding = false;
+
 private:
     // For ProcessLowerMiniseg
     bool inview;
diff --git a/src/rendering/hwrenderer/scene/hw_meshcache.cpp b/src/rendering/hwrenderer/scene/hw_meshcache.cpp
new file mode 100644
index 000000000..5c63f4165
--- /dev/null
+++ b/src/rendering/hwrenderer/scene/hw_meshcache.cpp
@@ -0,0 +1,90 @@
+
+#include "hw_meshcache.h"
+#include "hw_drawinfo.h"
+#include "hw_drawstructs.h"
+#include "hw_mesh.h"
+#include "g_levellocals.h"
+
+EXTERN_CVAR(Bool, gl_texture)
+EXTERN_CVAR(Float, gl_mask_threshold)
+
+HWMeshCache meshcache;
+
+void HWMeshCache::Update(FRenderViewpoint& vp)
+{
+	auto level = vp.ViewLevel;
+	unsigned int count = level->sectors.Size();
+	Sectors.Resize(count);
+	for (unsigned int i = 0; i < count; i++)
+	{
+		auto sector = &level->sectors[i];
+		if (Sectors[i].Sector != sector) // Note: this is just a stupid way to detect we changed map. What is the proper way?
+		{
+			Sectors[i].Sector = sector;
+			Sectors[i].Update(vp);
+		}
+	}
+}
+
+void HWCachedSector::Update(FRenderViewpoint& vp)
+{
+	HWDrawInfo* di = HWDrawInfo::StartDrawInfo(vp.ViewLevel, nullptr, vp, nullptr);
+	di->MeshBuilding = true;
+
+	// Add all the walls to the draw lists
+
+	for (line_t* line : Sector->Lines)
+	{
+		side_t* side = (line->sidedef[0]->sector == Sector) ? line->sidedef[0] : line->sidedef[1];
+
+		HWWall wall;
+		wall.sub = Sector->subsectors[0];
+		wall.Process(di, side->segs[0], Sector, (line->sidedef[0]->sector == Sector) ? line->backsector : line->frontsector);
+	}
+
+	// Convert draw lists to meshes
+
+	MeshBuilder state;
+
+	state.SetDepthMask(true);
+	state.EnableFog(true);
+	state.SetRenderStyle(STYLE_Source);
+
+	di->drawlists[GLDL_PLAINWALLS].SortWalls();
+	di->drawlists[GLDL_PLAINFLATS].SortFlats();
+	di->drawlists[GLDL_MASKEDWALLS].SortWalls();
+	di->drawlists[GLDL_MASKEDFLATS].SortFlats();
+	di->drawlists[GLDL_MASKEDWALLSOFS].SortWalls();
+
+	// Part 1: solid geometry. This is set up so that there are no transparent parts
+	state.SetDepthFunc(DF_Less);
+	state.AlphaFunc(Alpha_GEqual, 0.f);
+	state.ClearDepthBias();
+	state.EnableTexture(gl_texture);
+	state.EnableBrightmap(true);
+	di->drawlists[GLDL_PLAINWALLS].DrawWalls(di, state, false);
+	di->drawlists[GLDL_PLAINFLATS].DrawFlats(di, state, false);
+	Opaque = state.Create();
+
+	// Part 2: masked geometry. This is set up so that only pixels with alpha>gl_mask_threshold will show
+	state.AlphaFunc(Alpha_GEqual, gl_mask_threshold);
+	di->drawlists[GLDL_MASKEDWALLS].DrawWalls(di, state, false);
+	di->drawlists[GLDL_MASKEDFLATS].DrawFlats(di, state, false);
+	Translucent = state.Create();
+
+	// Part 3: masked geometry with polygon offset. This list is empty most of the time so only waste time on it when in use.
+	if (di->drawlists[GLDL_MASKEDWALLSOFS].Size() > 0)
+	{
+		state.SetDepthBias(-1, -128);
+		di->drawlists[GLDL_MASKEDWALLSOFS].DrawWalls(di, state, false);
+		state.ClearDepthBias();
+		TranslucentDepthBiased = state.Create();
+	}
+	else
+	{
+		TranslucentDepthBiased.reset();
+	}
+
+	di->MeshBuilding = false;
+	di->EndDrawInfo();
+}
diff --git a/src/rendering/hwrenderer/scene/hw_meshcache.h b/src/rendering/hwrenderer/scene/hw_meshcache.h
new file mode 100644
index 000000000..868ef686c
--- /dev/null
+++ b/src/rendering/hwrenderer/scene/hw_meshcache.h
@@ -0,0 +1,30 @@
+#pragma once
+
+#include "hw_mesh.h"
+#include "r_defs.h"
+
+struct FRenderViewpoint;
+
+class HWCachedSector
+{
+public:
+	sector_t* Sector = nullptr;
+
+	std::unique_ptr<Mesh> Opaque;
+	std::unique_ptr<Mesh> Translucent;
+	std::unique_ptr<Mesh> TranslucentDepthBiased;
+
+	void Update(FRenderViewpoint& vp);
+};
+
+class HWMeshCache
+{
+public:
+	void Update(FRenderViewpoint& vp);
+
+	TArray<HWCachedSector> Sectors;
+
+private:
+};
+
+extern HWMeshCache meshcache;
diff --git a/src/rendering/hwrenderer/scene/hw_walls.cpp b/src/rendering/hwrenderer/scene/hw_walls.cpp
index d0bfec9cd..4df4342c3 100644
--- a/src/rendering/hwrenderer/scene/hw_walls.cpp
+++ b/src/rendering/hwrenderer/scene/hw_walls.cpp
@@ -565,6 +565,9 @@ void HWWall::PutWall(HWDrawInfo *di, bool translucent)
 
 void HWWall::PutPortal(HWDrawInfo *di, int ptype, int plane)
 {
+	if (di->MeshBuilding)
+		return;
+
 	HWPortal * portal = nullptr;
 
 	MakeVertices(di, *screen->RenderState(), false);