diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index b1811eb45..c79452bb5 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -6194,7 +6194,7 @@ void HWR_RenderPlayerView(INT32 viewnumber, player_t *player)
 	}
 
 	// note: sets viewangle, viewx, viewy, viewz
-	R_SetupFrame(player, false); // This can stay false because it is only used to set viewsky in r_main.c, which isn't used here
+	R_SetupFrame(player);
 
 	// copy view cam position for local use
 	dup_viewx = viewx;
diff --git a/src/p_setup.c b/src/p_setup.c
index 0602865a9..af4f1f9dd 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3147,7 +3147,6 @@ boolean P_SetupLevel(boolean skipprecip)
 		savedata.lives = 0;
 	}
 
-	skyVisible = skyVisible1 = skyVisible2 = true; // assume the skybox is visible on level load.
 	if (loadprecip) // uglier hack
 	{ // to make a newly loaded level start on the second frame.
 		INT32 buf = gametic % BACKUPTICS;
diff --git a/src/r_bsp.c b/src/r_bsp.c
index 5643e777e..58d69ddf4 100644
--- a/src/r_bsp.c
+++ b/src/r_bsp.c
@@ -15,6 +15,7 @@
 #include "g_game.h"
 #include "r_local.h"
 #include "r_state.h"
+#include "r_portal.h" // Add seg portals
 
 #include "r_splats.h"
 #include "p_local.h" // camera
diff --git a/src/r_main.c b/src/r_main.c
index cab0490bf..c9513e390 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -66,8 +66,6 @@ size_t loopcount;
 fixed_t viewx, viewy, viewz;
 angle_t viewangle, aimingangle;
 fixed_t viewcos, viewsin;
-boolean viewsky, skyVisible;
-boolean skyVisible1, skyVisible2; // saved values of skyVisible for P1 and P2, for splitscreen
 sector_t *viewsector;
 player_t *viewplayer;
 
@@ -739,7 +737,7 @@ static void R_SetupFreelook(void)
 
 #undef AIMINGTODY
 
-void R_SetupFrame(player_t *player, boolean skybox)
+void R_SetupFrame(player_t *player)
 {
 	camera_t *thiscam;
 	boolean chasecam = false;
@@ -769,7 +767,6 @@ void R_SetupFrame(player_t *player, boolean skybox)
 	else if (!chasecam)
 		thiscam->chase = false;
 
-	viewsky = !skybox;
 	if (player->awayviewtics)
 	{
 		// cut-away view stuff
@@ -858,7 +855,6 @@ void R_SkyboxFrame(player_t *player)
 		thiscam = &camera;
 
 	// cut-away view stuff
-	viewsky = true;
 	viewmobj = skyboxmo[0];
 #ifdef PARANOIA
 	if (!viewmobj)
@@ -1022,9 +1018,6 @@ static void R_PortalFrame(portal_t *portal)
 
 void R_RenderPlayerView(player_t *player)
 {
-	portal_t *portal;
-	const boolean skybox = (skyboxmo[0] && cv_skybox.value);
-
 	if (cv_homremoval.value && player == &players[displayplayer]) // if this is display player 1
 	{
 		if (cv_homremoval.value == 1)
@@ -1033,37 +1026,7 @@ void R_RenderPlayerView(player_t *player)
 			V_DrawFill(0, 0, BASEVIDWIDTH, BASEVIDHEIGHT, 32+(timeinmap&15));
 	}
 
-	// load previous saved value of skyVisible for the player
-	if (splitscreen && player == &players[secondarydisplayplayer])
-		skyVisible = skyVisible2;
-	else
-		skyVisible = skyVisible1;
-
-	Portal_InitList();
-
-	if (skybox && skyVisible)
-	{
-		R_SkyboxFrame(player);
-
-		R_ClearClipSegs();
-		R_ClearDrawSegs();
-		R_ClearPlanes();
-		R_ClearSprites();
-#ifdef FLOORSPLATS
-		R_ClearVisibleFloorSplats();
-#endif
-
-		R_RenderBSPNode((INT32)numnodes - 1);
-		R_ClipSprites();
-		R_DrawPlanes();
-#ifdef FLOORSPLATS
-		R_DrawVisibleFloorSplats();
-#endif
-		R_DrawMasked();
-	}
-
-	R_SetupFrame(player, skybox);
-	skyVisible = false;
+	R_SetupFrame(player);
 	framecount++;
 	validcount++;
 
@@ -1075,6 +1038,7 @@ void R_RenderPlayerView(player_t *player)
 #ifdef FLOORSPLATS
 	R_ClearVisibleFloorSplats();
 #endif
+	Portal_InitList();
 
 	// check for new console commands.
 	NetUpdate();
@@ -1086,7 +1050,9 @@ void R_RenderPlayerView(player_t *player)
 	mytotal = 0;
 	ProfZeroTimer();
 #endif
+
 	R_RenderBSPNode((INT32)numnodes - 1);
+
 	R_ClipSprites();
 #ifdef TIMING
 	RDMSR(0x10, &mycount);
@@ -1096,9 +1062,15 @@ void R_RenderPlayerView(player_t *player)
 #endif
 //profile stuff ---------------------------------------------------------
 
+	// Add skybox portals caused by sky visplanes.
+	if (cv_skybox.value)
+		Portal_AddSkyboxPortals();
+
 	// Portal rendering. Hijacks the BSP traversal.
 	if (portal_base)
 	{
+		portal_t *portal;
+
 		for(portal = portal_base; portal; portal = portal_base)
 		{
 			portalrender = portal->pass; // Recursiveness depth.
@@ -1135,16 +1107,6 @@ void R_RenderPlayerView(player_t *player)
 	// draw mid texture and sprite
 	// And now 3D floors/sides!
 	R_DrawMasked();
-
-	// Check for new console commands.
-	NetUpdate();
-
-	// save value to skyVisible1 or skyVisible2
-	// this is so that P1 can't affect whether P2 can see a skybox or not, or vice versa
-	if (splitscreen && player == &players[secondarydisplayplayer])
-		skyVisible2 = skyVisible;
-	else
-		skyVisible1 = skyVisible;
 }
 
 // =========================================================================
diff --git a/src/r_main.h b/src/r_main.h
index 6ae5aa221..1d82a01b9 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -94,7 +94,7 @@ void R_ExecuteSetViewSize(void);
 
 void R_SkyboxFrame(player_t *player);
 
-void R_SetupFrame(player_t *player, boolean skybox);
+void R_SetupFrame(player_t *player);
 // Called by G_Drawer.
 void R_RenderPlayerView(player_t *player);
 
diff --git a/src/r_plane.c b/src/r_plane.c
index 5cd9b26b5..18e5fda52 100644
--- a/src/r_plane.c
+++ b/src/r_plane.c
@@ -23,6 +23,8 @@
 #include "r_state.h"
 #include "r_splats.h" // faB(21jan):testing
 #include "r_sky.h"
+#include "r_portal.h"
+
 #include "v_video.h"
 #include "w_wad.h"
 #include "z_zone.h"
@@ -679,16 +681,6 @@ static void R_DrawSkyPlane(visplane_t *pl)
 	INT32 x;
 	INT32 angle;
 
-	// If we're not supposed to draw the sky (e.g. for skyboxes), don't do anything!
-	// This probably utterly ruins sky rendering for FOFs and polyobjects, unfortunately
-	if (!viewsky)
-	{
-		// Mark that the sky was visible here for next tic
-		// (note: this is a hack and it sometimes can cause HOMs to appear for a tic IIRC)
-		skyVisible = true;
-		return;
-	}
-
 	// Reset column drawer function (note: couldn't we just call walldrawerfunc directly?)
 	// (that is, unless we'll need to switch drawers in future for some reason)
 	wallcolfunc = walldrawerfunc;
@@ -1186,3 +1178,31 @@ void R_PlaneBounds(visplane_t *plane)
 	plane->high = hi;
 	plane->low = low;
 }
+
+/** Creates portals for the currently existing sky visplanes.
+ * The visplanes are also removed and cleared from the list.
+ */
+void Portal_AddSkyboxPortals (void)
+{
+	visplane_t *pl;
+	INT32 i;
+	UINT16 count = 0;
+
+	for (i = 0; i < MAXVISPLANES; i++, pl++)
+	{
+		for (pl = visplanes[i]; pl; pl = pl->next)
+		{
+			if (pl->picnum == skyflatnum)
+			{
+				Portal_AddSkybox(pl);
+
+				pl->minx = 0;
+				pl->maxx = -1;
+
+				count++;
+			}
+		}
+	}
+
+	CONS_Debug(DBG_RENDER, "Skybox portals: %d\n", count);
+}
diff --git a/src/r_plane.h b/src/r_plane.h
index bdfc40058..c101e3218 100644
--- a/src/r_plane.h
+++ b/src/r_plane.h
@@ -120,4 +120,6 @@ typedef struct planemgr_s
 
 extern visffloor_t ffloor[MAXFFLOORS];
 extern INT32 numffloors;
+
+void Portal_AddSkyboxPortals (void);
 #endif
diff --git a/src/r_portal.c b/src/r_portal.c
index 2675ae968..15efc79ba 100644
--- a/src/r_portal.c
+++ b/src/r_portal.c
@@ -13,7 +13,9 @@
 
 #include "r_portal.h"
 #include "r_plane.h"
-#include "r_main.h" // viewheight, viewwidth
+#include "r_main.h"
+#include "doomstat.h"
+#include "p_spec.h" // Skybox viewpoints
 #include "z_zone.h"
 
 UINT8 portalrender;			/**< When rendering a portal, it establishes the depth of the current BSP traversal. */
@@ -39,7 +41,7 @@ void Portal_InitList (void)
  * the function is called, so it is useful for converting one-sided
  * lines into portals.
  */
-void Portal_ClipStoreFromRange (portal_t* portal)
+void Portal_ClipRange (portal_t* portal)
 {
 	INT32 start	= portal->start;
 	INT32 end	= portal->end;
@@ -179,9 +181,80 @@ void Portal_Add2Lines (const INT32 line1, const INT32 line2, const INT32 x1, con
 
 	portal->clipline = line2;
 
-	Portal_ClipStoreFromRange(portal);
+	Portal_ClipRange(portal);
 
 	portalline = true; // this tells R_StoreWallRange that curline is a portal seg
 }
 
+/** Store the clipping window for a portal using a visplane.
+ *
+ * Since visplanes top/bottom windows work in an identical way,
+ * it can just be copied almost directly.
+ */
+static void Portal_ClipVisplane (const visplane_t* plane, portal_t* portal)
+{
+	INT16 start	= portal->start;
+	INT16 end	= portal->end;
+	INT32 i;
 
+	for (i = 0; i < end - start; i++)
+	{
+		portal->ceilingclip[i] = plane->top[i + start];
+		portal->floorclip[i] = plane->bottom[i + start] + 1;
+	}
+}
+
+extern INT32 viewwidth;
+
+/** Creates a skybox portal out of a visplane.
+ *
+ * Applies the necessary offsets and rotation to give
+ * a depth illusion to the skybox.
+ */
+void Portal_AddSkybox (const visplane_t* plane)
+{
+	INT16 start = plane->minx;
+	INT16 end = plane->maxx + 1;
+	mapheader_t *mh;
+	portal_t* portal;
+
+	if (!(start < end))
+		return;
+
+	portal = Portal_Add(start, end);
+
+	Portal_ClipVisplane(plane, portal);
+
+	portal->viewx = skyboxmo[0]->x;
+	portal->viewy = skyboxmo[0]->y;
+	portal->viewz = skyboxmo[0]->z;
+	portal->viewangle = viewangle + skyboxmo[0]->angle;
+
+	mh = mapheaderinfo[gamemap-1];
+
+	// If a relative viewpoint exists, offset the viewpoint.
+	if (skyboxmo[1])
+	{
+		fixed_t x = 0, y = 0;
+
+		if (mh->skybox_scalex > 0)
+			x = (viewx - skyboxmo[1]->x) / mh->skybox_scalex;
+		else if (mh->skybox_scalex < 0)
+			x = (viewx - skyboxmo[1]->x) * -mh->skybox_scalex;
+
+		if (mh->skybox_scaley > 0)
+			y = (viewy - skyboxmo[1]->y) / mh->skybox_scaley;
+		else if (mh->skybox_scaley < 0)
+			y = (viewy - skyboxmo[1]->y) * -mh->skybox_scaley;
+
+		portal->viewx += x;
+		portal->viewy += y;
+	}
+
+	if (mh->skybox_scalez > 0)
+		portal->viewz += viewz / mh->skybox_scalez;
+	else if (mh->skybox_scalez < 0)
+		portal->viewz += viewz * -mh->skybox_scalez;
+
+	portal->clipline = -1;
+}
diff --git a/src/r_portal.h b/src/r_portal.h
index 8df3db415..9426aaf6a 100644
--- a/src/r_portal.h
+++ b/src/r_portal.h
@@ -12,9 +12,9 @@
 /// \brief Software renderer portal struct, functions, linked list extern.
 
 #include "r_data.h"
+#include "r_plane.h" // visplanes
 
-
-/** Portal structure.
+/** Portal structure for the software renderer.
  */
 typedef struct portal_s
 {
@@ -44,6 +44,7 @@ extern UINT8 portalrender;
 void Portal_InitList	(void);
 void Portal_Remove		(portal_t* portal);
 void Portal_Add2Lines	(const INT32 line1, const INT32 line2, const INT32 x1, const INT32 x2);
+void Portal_AddSkybox	(const visplane_t* plane);
 
-void Portal_ClipStoreFromRange (portal_t* portal);
+void Portal_ClipRange (portal_t* portal);
 void Portal_ClipApply (const portal_t* portal);
diff --git a/src/r_state.h b/src/r_state.h
index 9c8ce51d6..4959b55bc 100644
--- a/src/r_state.h
+++ b/src/r_state.h
@@ -80,8 +80,6 @@ extern side_t *sides;
 //
 extern fixed_t viewx, viewy, viewz;
 extern angle_t viewangle, aimingangle;
-extern boolean viewsky, skyVisible;
-extern boolean skyVisible1, skyVisible2; // saved values of skyVisible for P1 and P2, for splitscreen
 extern sector_t *viewsector;
 extern player_t *viewplayer;
 extern UINT8 portalrender;