diff --git a/.travis.yml b/.travis.yml
index 6962cbaff..39b3ee086 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -93,16 +93,15 @@ matrix:
     - os: linux
       compiler: clang
       env:
-        - CLANG_VERSION=6.0
+        - CLANG_VERSION=7
         - CMAKE_OPTIONS="-DCMAKE_BUILD_TYPE=MinSizeRel -DDYN_OPENAL=NO -DDYN_SNDFILE=NO -DDYN_MPG123=NO -DDYN_FLUIDSYNTH=NO"
       addons:
         apt:
           sources:
             - ubuntu-toolchain-r-test
-            - llvm-toolchain-trusty-6.0
+            - llvm-toolchain-trusty-7
           packages:
-            - clang-6.0
-            - libstdc++-5-dev
+            - clang-7
             - libsdl2-dev
             - libgme-dev
             - libopenal-dev
diff --git a/src/hwrenderer/data/hw_viewpointbuffer.h b/src/hwrenderer/data/hw_viewpointbuffer.h
index 2e1f1e620..3a770ec91 100644
--- a/src/hwrenderer/data/hw_viewpointbuffer.h
+++ b/src/hwrenderer/data/hw_viewpointbuffer.h
@@ -16,7 +16,7 @@ class GLViewpointBuffer
 	unsigned int mByteSize;
 	TArray<bool> mClipPlaneInfo;
 	
-	unsigned int m2DWidth = ~0u, m2DHeight = ~0u;
+	int m2DWidth = -1, m2DHeight = -1;
 
 	unsigned int mBlockSize;
 
diff --git a/src/p_ceiling.cpp b/src/p_ceiling.cpp
index 5eb8157f5..0f37e3379 100644
--- a/src/p_ceiling.cpp
+++ b/src/p_ceiling.cpp
@@ -428,7 +428,7 @@ bool P_CreateCeiling(sector_t *sec, DCeiling::ECeiling type, line_t *line, int t
 				switch (change & 3)
 				{
 					case 1:		// type is zeroed
-						ceiling->m_NewSpecial.Clear();
+						ceiling->m_NewSpecial = {};
 						ceiling->m_Type = DCeiling::genCeilingChg0;
 						break;
 					case 2:		// type is copied
@@ -447,7 +447,7 @@ bool P_CreateCeiling(sector_t *sec, DCeiling::ECeiling type, line_t *line, int t
 			switch (change & 3)
 			{
 				case 1:		// type is zeroed
-					ceiling->m_NewSpecial.Clear();
+					ceiling->m_NewSpecial = {};
 					ceiling->m_Type = DCeiling::genCeilingChg0;
 					break;
 				case 2:		// type is copied
diff --git a/src/p_floor.cpp b/src/p_floor.cpp
index d0b6cb077..7141a842e 100644
--- a/src/p_floor.cpp
+++ b/src/p_floor.cpp
@@ -229,7 +229,7 @@ void DFloor::SetFloorChangeType (sector_t *sec, int change)
 	switch (change & 3)
 	{
 	case 1:
-		m_NewSpecial.Clear();
+		m_NewSpecial = {};
 		m_Type = DFloor::genFloorChg0;
 		break;
 	case 2:
@@ -828,7 +828,7 @@ bool EV_DoDonut (int tag, line_t *line, double pillarspeed, double slimespeed)
 			floor->m_Speed = slimespeed;
 			floor->m_Instant = false;
 			floor->m_Texture = s3->GetTexture(sector_t::floor);
-			floor->m_NewSpecial.Clear();
+			floor->m_NewSpecial = {};
 			height = s3->FindHighestFloorPoint (&spot);
 			floor->m_FloorDestDist = s2->floorplane.PointToDist (spot, height);
 			floor->StartFloorSound ();
diff --git a/src/p_spec.h b/src/p_spec.h
index 6dc118658..61cc7b2f0 100644
--- a/src/p_spec.h
+++ b/src/p_spec.h
@@ -439,7 +439,7 @@ protected:
 
 	// [RH] Need these for BOOM-ish transferring ceilings
 	FTextureID	m_Texture;
-	secspecial_t m_NewSpecial;
+	secspecial_t m_NewSpecial{};
 
 	// ID
 	int 		m_Tag;
@@ -536,7 +536,7 @@ public:
 	bool		m_Hexencrush;
 	bool		m_Instant;
 	int 		m_Direction;
-	secspecial_t m_NewSpecial;
+	secspecial_t m_NewSpecial{};
 	FTextureID	m_Texture;
 	double	 	m_FloorDestDist;
 	double	 	m_Speed;
diff --git a/src/polyrenderer/scene/poly_cull.cpp b/src/polyrenderer/scene/poly_cull.cpp
index 4bda49b7c..6668e2f2b 100644
--- a/src/polyrenderer/scene/poly_cull.cpp
+++ b/src/polyrenderer/scene/poly_cull.cpp
@@ -164,7 +164,7 @@ void PolyCull::CullSubsector(subsector_t *sub)
 		angle_t angle2 = PointToPseudoAngle(line->v1->fX(), line->v1->fY());
 		angle_t angle1 = PointToPseudoAngle(line->v2->fX(), line->v2->fY());
 		bool lineVisible = !IsSegmentCulled(angle1, angle2);
-		if (lineVisible && line->backsector == nullptr)
+		if (lineVisible && IsSolidLine(line))
 		{
 			MarkSegmentCulled(angle1, angle2);
 		}
@@ -182,6 +182,52 @@ void PolyCull::CullSubsector(subsector_t *sub)
 	SubsectorDepths[sub->Index()] = subsectorDepth;
 }
 
+bool PolyCull::IsSolidLine(seg_t *line)
+{
+	// One-sided
+	if (!line->backsector) return true;
+
+	// Portal
+	if (line->linedef && line->linedef->isVisualPortal() && line->sidedef == line->linedef->sidedef[0]) return true;
+
+	double frontCeilingZ1 = line->frontsector->ceilingplane.ZatPoint(line->v1);
+	double frontFloorZ1 = line->frontsector->floorplane.ZatPoint(line->v1);
+	double frontCeilingZ2 = line->frontsector->ceilingplane.ZatPoint(line->v2);
+	double frontFloorZ2 = line->frontsector->floorplane.ZatPoint(line->v2);
+
+	double backCeilingZ1 = line->backsector->ceilingplane.ZatPoint(line->v1);
+	double backFloorZ1 = line->backsector->floorplane.ZatPoint(line->v1);
+	double backCeilingZ2 = line->backsector->ceilingplane.ZatPoint(line->v2);
+	double backFloorZ2 = line->backsector->floorplane.ZatPoint(line->v2);
+
+	// Closed door.
+	if (backCeilingZ1 <= frontFloorZ1 && backCeilingZ2 <= frontFloorZ2) return true;
+	if (backFloorZ1 >= frontCeilingZ1 && backFloorZ2 >= frontCeilingZ2) return true;
+
+	// properly render skies (consider door "open" if both ceilings are sky)
+	if (line->backsector->GetTexture(sector_t::ceiling) == skyflatnum && line->frontsector->GetTexture(sector_t::ceiling) == skyflatnum) return false;
+
+	// if door is closed because back is shut:
+	if (!(backCeilingZ1 <= backFloorZ1 && backCeilingZ2 <= backFloorZ2)) return false;
+
+	// preserve a kind of transparent door/lift special effect:
+	if (((backCeilingZ1 >= frontCeilingZ1 && backCeilingZ2 >= frontCeilingZ2) || line->sidedef->GetTexture(side_t::top).isValid())
+		&& ((backFloorZ1 <= frontFloorZ1 && backFloorZ2 <= frontFloorZ2) || line->sidedef->GetTexture(side_t::bottom).isValid()))
+	{
+		// killough 1/18/98 -- This function is used to fix the automap bug which
+		// showed lines behind closed doors simply because the door had a dropoff.
+		//
+		// It assumes that Doom has already ruled out a door being closed because
+		// of front-back closure (e.g. front floor is taller than back ceiling).
+
+		// This fixes the automap floor height bug -- killough 1/18/98:
+		// killough 4/7/98: optimize: save result in doorclosed for use in r_segs.c
+		return true;
+	}
+
+	return false;
+}
+
 bool PolyCull::IsSegmentCulled(angle_t startAngle, angle_t endAngle) const
 {
 	if (startAngle > endAngle)
diff --git a/src/polyrenderer/scene/poly_cull.h b/src/polyrenderer/scene/poly_cull.h
index 53b14c9cc..81fa19387 100644
--- a/src/polyrenderer/scene/poly_cull.h
+++ b/src/polyrenderer/scene/poly_cull.h
@@ -56,6 +56,8 @@ private:
 	void MarkViewFrustum();
 	void InvertSegments();
 
+	static bool IsSolidLine(seg_t *line);
+
 	bool IsSegmentCulled(angle_t angle1, angle_t angle2) const;
 
 	void CullNode(void *node);
diff --git a/src/polyrenderer/scene/poly_model.cpp b/src/polyrenderer/scene/poly_model.cpp
index 28288504e..39695c016 100644
--- a/src/polyrenderer/scene/poly_model.cpp
+++ b/src/polyrenderer/scene/poly_model.cpp
@@ -39,6 +39,7 @@ void PolyRenderModel(PolyRenderThread *thread, const Mat4f &worldToClip, uint32_
 	renderer.AddLights(actor);
 	renderer.RenderModel(x, y, z, smf, actor, r_viewpoint.TicFrac);
 	PolyTriangleDrawer::SetModelVertexShader(thread->DrawQueue, -1, -1, 0.0f);
+	PolyTriangleDrawer::SetTransform(thread->DrawQueue, thread->FrameMemory->NewObject<Mat4f>(worldToClip), nullptr);
 }
 
 void PolyRenderHUDModel(PolyRenderThread *thread, const Mat4f &worldToClip, uint32_t stencilValue, DPSprite *psp, float ofsx, float ofsy)
diff --git a/src/r_defs.h b/src/r_defs.h
index 6c1d0da67..ffd504ea4 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -588,16 +588,6 @@ struct secspecial_t
 	short damageinterval;	// Interval for damage application
 	short leakydamage;		// chance of leaking through radiation suit
 	int Flags;
-
-	secspecial_t()
-	{
-		Clear();
-	}
-
-	void Clear()
-	{
-		memset(this, 0, sizeof(*this));
-	}
 };
 
 FSerializer &Serialize(FSerializer &arc, const char *key, secspecial_t &spec, secspecial_t *def);
diff --git a/src/s_sound.cpp b/src/s_sound.cpp
index 30e6f918e..be12d3693 100644
--- a/src/s_sound.cpp
+++ b/src/s_sound.cpp
@@ -2737,8 +2737,8 @@ DEFINE_ACTION_FUNCTION(DObject, S_ChangeMusic)
 	PARAM_PROLOGUE;
 	PARAM_STRING(music);
 	PARAM_INT_DEF(order);
-	PARAM_BOOL(looping);
-	PARAM_BOOL(force);
+	PARAM_BOOL_DEF(looping);
+	PARAM_BOOL_DEF(force);
 	ACTION_RETURN_BOOL(S_ChangeMusic(music, order, looping, force));
 }