diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c89b881798..4ebce76cdc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -229,13 +229,12 @@ include_directories( ${OPENGL_INCLUDE_DIR} )
 
 if( NOT NO_OPENAL )
     find_package( OpenAL )
-	mark_as_advanced(CLEAR OPENAL_LIBRARY OPENAL_INCLUDE_DIR)
-    if( OPENAL_FOUND )
+	mark_as_advanced(CLEAR OPENAL_INCLUDE_DIR)
+    if( OPENAL_INCLUDE_DIR )
         include_directories( ${OPENAL_INCLUDE_DIR} )
-        set( ZDOOM_LIBS ${OPENAL_LIBRARY} ${ZDOOM_LIBS} )
-    else( OPENAL_FOUND )
-        set( NO_OPENAL ON )
-    endif( OPENAL_FOUND )
+    else( OPENAL_INCLUDE_DIR )
+		set( NO_OPENAL ON )
+    endif( OPENAL_INCLUDE_DIR )
 endif( NOT NO_OPENAL )
 
 if( NOT NO_FMOD )
diff --git a/src/dsectoreffect.cpp b/src/dsectoreffect.cpp
index 6732a19dc8..7bc9fc400e 100644
--- a/src/dsectoreffect.cpp
+++ b/src/dsectoreffect.cpp
@@ -95,11 +95,11 @@ void DMover::Serialize (FArchive &arc)
 	arc << interpolation;
 }
 
-void DMover::StopInterpolation()
+void DMover::StopInterpolation(bool force)
 {
 	if (interpolation != NULL)
 	{
-		interpolation->DelRef();
+		interpolation->DelRef(force);
 		interpolation = NULL;
 	}
 }
diff --git a/src/dsectoreffect.h b/src/dsectoreffect.h
index 95e1178aa3..3788c6d88f 100644
--- a/src/dsectoreffect.h
+++ b/src/dsectoreffect.h
@@ -36,7 +36,7 @@ protected:
 	DMover ();
 	void Serialize (FArchive &arc);
 	void Destroy();
-	void StopInterpolation();
+	void StopInterpolation(bool force = false);
 	inline EResult MoveFloor (fixed_t speed, fixed_t dest, int crush, int direction, bool hexencrush)
 	{
 		return MovePlane (speed, dest, crush, 0, direction, hexencrush);
diff --git a/src/fragglescript/t_func.cpp b/src/fragglescript/t_func.cpp
index 3060c65aa1..be838d54bc 100644
--- a/src/fragglescript/t_func.cpp
+++ b/src/fragglescript/t_func.cpp
@@ -1571,7 +1571,7 @@ public:
 		bool res = DMover::crushed != MoveFloor(speed, dest, crush, direction, false);
 		Destroy();
 		m_Sector->floordata=NULL;
-		StopInterpolation();
+		StopInterpolation(true);
 		m_Sector=NULL;
 		return res;
 	}
@@ -1656,6 +1656,14 @@ public:
 		m_Speed=movespeed;
 		m_Direction = _m_Direction;
 		m_FloorDestDist = moveheight;
+
+		// Do not interpolate instant movement floors.
+		fixed_t movedist = abs(-sec->floorplane.d - moveheight);
+		if (m_Speed >= movedist)
+		{
+			StopInterpolation(true);
+		}
+
 		StartFloorSound();
 	}
 };
@@ -1713,7 +1721,7 @@ public:
 		bool res = DMover::crushed != MoveCeiling(speed, dest, crush, direction, false);
 		Destroy();
 		m_Sector->ceilingdata=NULL;
-		StopInterpolation ();
+		StopInterpolation (true);
 		m_Sector=NULL;
 		return res;
 	}
@@ -1806,7 +1814,7 @@ public:
 		fixed_t movedist = abs(sec->ceilingplane.d - m_BottomHeight);
 		if (m_Speed >= movedist)
 		{
-			StopInterpolation ();
+			StopInterpolation (true);
 			m_Silent=2;
 		}
 		PlayCeilingSound();
diff --git a/src/g_heretic/a_hereticweaps.cpp b/src/g_heretic/a_hereticweaps.cpp
index c6ccc6ae6a..92cffd64b6 100644
--- a/src/g_heretic/a_hereticweaps.cpp
+++ b/src/g_heretic/a_hereticweaps.cpp
@@ -626,7 +626,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_DeathBallImpact)
 			}
 			else
 			{ // Seek
-				self->angle = self->AngleTo(target);
+				angle = self->AngleTo(target);
 				newAngle = true;
 			}
 		}
diff --git a/src/p_ceiling.cpp b/src/p_ceiling.cpp
index 3203cf7779..24ab121c41 100644
--- a/src/p_ceiling.cpp
+++ b/src/p_ceiling.cpp
@@ -412,7 +412,7 @@ DCeiling *DCeiling::Create(sector_t *sec, DCeiling::ECeiling type, line_t *line,
 	}
 	if (ceiling->m_Speed >= movedist)
 	{
-		ceiling->StopInterpolation();
+		ceiling->StopInterpolation(true);
 	}
 
 	// set texture/type change properties
diff --git a/src/p_floor.cpp b/src/p_floor.cpp
index 013f0a78ff..eb9aaa4f9a 100644
--- a/src/p_floor.cpp
+++ b/src/p_floor.cpp
@@ -478,7 +478,7 @@ bool EV_DoFloor (DFloor::EFloor floortype, line_t *line, int tag,
 			(floor->m_Direction<0 && floor->m_FloorDestDist<sec->floorplane.d) ||	// moving down but going up
 			(floor->m_Speed >= abs(sec->floorplane.d - floor->m_FloorDestDist)))	// moving in one step
 		{
-			floor->StopInterpolation();
+			floor->StopInterpolation(true);
 
 			// [Graf Zahl]
 			// Don't make sounds for instant movement hacks but make an exception for
diff --git a/src/p_terrain.cpp b/src/p_terrain.cpp
index af8de5cab2..9d0b8456ad 100644
--- a/src/p_terrain.cpp
+++ b/src/p_terrain.cpp
@@ -627,13 +627,19 @@ static void ParseFloor (FScanner &sc)
 	FTextureID picnum;
 	int terrain;
 
+	bool opt = sc.CheckString("optional");
 	sc.MustGetString ();
+
 	picnum = TexMan.CheckForTexture (sc.String, FTexture::TEX_Flat,
 		FTextureManager::TEXMAN_Overridable|FTextureManager::TEXMAN_TryAny);
+
 	if (!picnum.Exists())
 	{
-		Printf ("Unknown flat %s\n", sc.String);
-		sc.MustGetString ();
+		if (!opt)
+		{
+			Printf("Unknown flat %s\n", sc.String);
+		}
+		sc.MustGetString();
 		return;
 	}
 	sc.MustGetString ();
diff --git a/src/r_data/r_interpolate.cpp b/src/r_data/r_interpolate.cpp
index 5f2632737b..4e0781a98a 100644
--- a/src/r_data/r_interpolate.cpp
+++ b/src/r_data/r_interpolate.cpp
@@ -344,9 +344,10 @@ int DInterpolation::AddRef()
 //
 //==========================================================================
 
-int DInterpolation::DelRef()
+int DInterpolation::DelRef(bool force)
 {
 	if (refcount > 0) --refcount;
+	if (force && refcount == 0) Destroy();
 	return refcount;
 }
 
@@ -943,20 +944,6 @@ DInterpolation *sector_t::SetInterpolation(int position, bool attach)
 //
 //==========================================================================
 
-void sector_t::StopInterpolation(int position)
-{
-	if (interpolations[position] != NULL)
-	{
-		interpolations[position]->DelRef();
-	}
-}
-
-//==========================================================================
-//
-//
-//
-//==========================================================================
-
 DInterpolation *FPolyObj::SetInterpolation()
 {
 	if (interpolation != NULL)
diff --git a/src/r_data/r_interpolate.h b/src/r_data/r_interpolate.h
index 29e8a61712..92e74c3f29 100644
--- a/src/r_data/r_interpolate.h
+++ b/src/r_data/r_interpolate.h
@@ -25,7 +25,7 @@ protected:
 
 public:
 	int AddRef();
-	int DelRef();
+	int DelRef(bool force = false);
 
 	virtual void Destroy();
 	virtual void UpdateInterpolation() = 0;
diff --git a/src/r_defs.h b/src/r_defs.h
index aae0a9d676..d67c633eba 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -542,7 +542,6 @@ struct sector_t
 	sector_t *GetHeightSec() const;
 
 	DInterpolation *SetInterpolation(int position, bool attach);
-	void StopInterpolation(int position);
 
 	ASkyViewpoint *GetSkyBox(int which);
 
diff --git a/src/sc_man_scanner.re b/src/sc_man_scanner.re
index 519ee4a1e7..7f15d862e2 100644
--- a/src/sc_man_scanner.re
+++ b/src/sc_man_scanner.re
@@ -55,6 +55,8 @@ std2:
 	/*!re2c
 		"/*"						{ goto comment; }	/* C comment */
 		"//" (any\"\n")* "\n"		{ goto newline; }	/* C++ comment */
+		("#region"|"#endregion") (any\"\n")* "\n"
+									{ goto newline; }	/* Region blocks [mxd] */
 
 		/* C Keywords */
 		'break'						{ RET(TK_Break); }
@@ -241,6 +243,8 @@ std2:
 	/*!re2c
 		"/*"						{ goto comment; }	/* C comment */
 		("//"|";") (any\"\n")* "\n"	{ goto newline; }	/* C++/Hexen comment */
+		("#region"|"#endregion") (any\"\n")* "\n"
+									{ goto newline; }	/* Region blocks [mxd] */
 
 		WSP+						{ goto std1; }		/* whitespace */
 		"\n"						{ goto newline; }
@@ -259,6 +263,8 @@ std2:
 	/*!re2c
 		"/*"					{ goto comment; }	/* C comment */
 		"//" (any\"\n")* "\n"	{ goto newline; }	/* C++ comment */
+		("#region"|"#endregion") (any\"\n")* "\n"
+									{ goto newline; }	/* Region blocks [mxd] */
 
 		WSP+					{ goto std1; }		/* whitespace */
 		"\n"					{ goto newline; }
diff --git a/src/sound/oalload.h b/src/sound/oalload.h
index 7d4e62287f..986131b2c9 100644
--- a/src/sound/oalload.h
+++ b/src/sound/oalload.h
@@ -1,7 +1,11 @@
 #ifndef OALDEF_H
 #define OALDEF_H
 
-#if defined _WIN32 && !defined NO_OPENAL
+#ifndef NO_OPENAL
+
+#ifndef _WIN32
+typedef void* FARPROC;
+#endif
 
 #define DEFINE_ENTRY(type, name) static type p_##name;
 #include "oaldef.h"
diff --git a/src/sound/oalsound.cpp b/src/sound/oalsound.cpp
index a5ec97f97e..6030c9142c 100644
--- a/src/sound/oalsound.cpp
+++ b/src/sound/oalsound.cpp
@@ -36,6 +36,8 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 #define USE_WINDOWS_DWORD
+#else
+#include <dlfcn.h>
 #endif
 
 #include "except.h"
@@ -61,14 +63,23 @@ CVAR (Bool, snd_efx, true, CVAR_ARCHIVE|CVAR_GLOBALCONFIG)
 
 #ifdef _WIN32
 static HMODULE hmodOpenAL;
+#define OPENALLIB "openal32.dll"
+#else
+static void* hmodOpenAL;
+#ifdef __APPLE__
+#define OPENALLIB "OpenAL.framework/OpenAL"
+#else
+#define OPENALLIB "libopenal.so"
+#endif
+#define LoadLibrary(x) dlopen((x), RTLD_LAZY)
+#define GetProcAddress(a,b) dlsym((a),(b))
+#define FreeLibrary(x) dlclose((x))
 #endif
 
 bool IsOpenALPresent()
 {
 #ifdef NO_OPENAL
 	return false;
-#elif !defined _WIN32
-	return true;
 #else
 	static bool cached_result = false;
 	static bool done = false;
@@ -78,10 +89,10 @@ bool IsOpenALPresent()
 		done = true;
 		if (hmodOpenAL == NULL)
 		{
-			hmodOpenAL = LoadLibrary(NicePath("$PROGDIR/openal32.dll"));
+			hmodOpenAL = LoadLibrary(NicePath("$PROGDIR/" OPENALLIB));
 			if (hmodOpenAL == NULL)
 			{
-				hmodOpenAL = LoadLibrary("openal32.dll");
+				hmodOpenAL = LoadLibrary(OPENALLIB);
 				if (hmodOpenAL == NULL)
 				{
 					return false;
@@ -90,7 +101,7 @@ bool IsOpenALPresent()
 			for(int i = 0; oalfuncs[i].name != NULL; i++)
 			{
 				*oalfuncs[i].funcaddr = GetProcAddress(hmodOpenAL, oalfuncs[i].name);
-				if (oalfuncs[i].funcaddr == NULL)
+				if (*oalfuncs[i].funcaddr == NULL)
 				{
 					FreeLibrary(hmodOpenAL);
 					hmodOpenAL = NULL;
diff --git a/wadsrc/static/actors/doom/fatso.txt b/wadsrc/static/actors/doom/fatso.txt
index 0b30393257..88eaef39b3 100644
--- a/wadsrc/static/actors/doom/fatso.txt
+++ b/wadsrc/static/actors/doom/fatso.txt
@@ -34,7 +34,7 @@ ACTOR Fatso
 		FATT H 10 BRIGHT A_FatAttack2
 		FATT IG 5 A_FaceTarget
 		FATT H 10 BRIGHT A_FatAttack3
-		FATT IG 5
+		FATT IG 5 A_FaceTarget
 		Goto See
 	Pain:
 		FATT J 3
diff --git a/wadsrc/static/actors/doom/painelemental.txt b/wadsrc/static/actors/doom/painelemental.txt
index 5951afd6b5..ab0cd5cc9a 100644
--- a/wadsrc/static/actors/doom/painelemental.txt
+++ b/wadsrc/static/actors/doom/painelemental.txt
@@ -29,8 +29,8 @@ ACTOR PainElemental
 	Missile:
 		PAIN D 5 A_FaceTarget
 		PAIN E 5 A_FaceTarget
-		PAIN F 4 BRIGHT A_FaceTarget
-		PAIN F 1 BRIGHT A_PainAttack
+		PAIN F 5 BRIGHT A_FaceTarget
+		PAIN F 0 BRIGHT A_PainAttack
 		Goto See
 	Pain:
 		PAIN G 6
diff --git a/wadsrc/static/actors/doom/revenant.txt b/wadsrc/static/actors/doom/revenant.txt
index ce072bec46..1a5045f345 100644
--- a/wadsrc/static/actors/doom/revenant.txt
+++ b/wadsrc/static/actors/doom/revenant.txt
@@ -31,7 +31,7 @@ ACTOR Revenant
 		SKEL AABBCCDDEEFF 2 A_Chase
 		Loop
 	Melee:
-		SKEL G 1 A_FaceTarget
+		SKEL G 0 A_FaceTarget
 		SKEL G 6 A_SkelWhoosh
 		SKEL H 6 A_FaceTarget
 		SKEL I 6 A_SkelFist
diff --git a/wadsrc/static/confont.lmp b/wadsrc/static/confont.lmp
index 3d46a3ca4c..6b68df2e3e 100644
Binary files a/wadsrc/static/confont.lmp and b/wadsrc/static/confont.lmp differ