diff --git a/src/swrenderer/scene/r_bsp.cpp b/src/swrenderer/scene/r_bsp.cpp
index 24937c7a9..2b3054e4f 100644
--- a/src/swrenderer/scene/r_bsp.cpp
+++ b/src/swrenderer/scene/r_bsp.cpp
@@ -96,148 +96,6 @@ WORD MirrorFlags;
 
 subsector_t *InSubsector;
 
-
-
-void R_StoreWallRange (int start, int stop);
-
-//==========================================================================
-//
-// R_ClipWallSegment
-//
-// Clips the given range of columns, possibly including it in the clip list.
-// Handles both windows (e.g. LineDefs with upper and lower textures) and
-// solid walls (e.g. single sided LineDefs [middle texture]) that entirely
-// block the view.
-//
-//==========================================================================
-
-bool R_ClipWallSegment (int first, int last, bool solid)
-{
-	cliprange_t *next, *start;
-	int i, j;
-	bool res = false;
-
-	// Find the first range that touches the range
-	// (adjacent pixels are touching).
-	start = solidsegs;
-	while (start->last < first)
-		start++;
-
-	if (first < start->first)
-	{
-		res = true;
-		if (last <= start->first)
-		{
-			// Post is entirely visible (above start).
-			R_StoreWallRange (first, last);
-			if (fake3D & FAKE3D_FAKEMASK)
-			{
-				return true;
-			}
-
-			// Insert a new clippost for solid walls.
-			if (solid)
-			{
-				if (last == start->first)
-				{
-					start->first = first;
-				}
-				else
-				{
-					next = newend;
-					newend++;
-					while (next != start)
-					{
-						*next = *(next-1);
-						next--;
-					}
-					next->first = first;
-					next->last = last;
-				}
-			}
-			return true;
-		}
-
-		// There is a fragment above *start.
-		R_StoreWallRange (first, start->first);
-
-		// Adjust the clip size for solid walls
-		if (solid && !(fake3D & FAKE3D_FAKEMASK))
-		{
-			start->first = first;
-		}
-	}
-
-	// Bottom contained in start?
-	if (last <= start->last)
-		return res;
-
-	next = start;
-	while (last >= (next+1)->first)
-	{
-		// There is a fragment between two posts.
-		R_StoreWallRange (next->last, (next+1)->first);
-		next++;
-		
-		if (last <= next->last)
-		{
-			// Bottom is contained in next.
-			last = next->last;
-			goto crunch;
-		}
-	}
-
-	// There is a fragment after *next.
-	R_StoreWallRange (next->last, last);
-
-crunch:
-	if (fake3D & FAKE3D_FAKEMASK)
-	{
-		return true;
-	}
-	if (solid)
-	{
-		// Adjust the clip size.
-		start->last = last;
-
-		if (next != start)
-		{
-			// Remove start+1 to next from the clip list,
-			// because start now covers their area.
-			for (i = 1, j = (int)(newend - next); j > 0; i++, j--)
-			{
-				start[i] = next[i];
-			}
-			newend = start+i;
-		}
-	}
-	return true;
-}
-
-bool R_CheckClipWallSegment (int first, int last)
-{
-	cliprange_t *start;
-
-	// Find the first range that touches the range
-	// (adjacent pixels are touching).
-	start = solidsegs;
-	while (start->last < first)
-		start++;
-
-	if (first < start->first)
-	{
-		return true;
-	}
-
-	// Bottom contained in start?
-	if (last > start->last)
-	{
-		return true;
-	}
-
-	return false;
-}
-
 //
 // killough 3/7/98: Hack floor/ceiling heights for deep water etc.
 //
@@ -703,7 +561,7 @@ void R_AddLine (seg_t *line)
 #endif
 	}
 
-	if (R_ClipWallSegment (WallC.sx1, WallC.sx2, solid))
+	if (R_ClipWallSegment(WallC.sx1, WallC.sx2, solid, R_StoreWallRange))
 	{
 		InSubsector->flags |= SSECF_DRAWN;
 	}
@@ -836,8 +694,6 @@ static bool R_CheckBBox (float *bspcoord)	// killough 1/28/98: static
 	double				rx1, ry1, rx2, ry2;
 	int					sx1, sx2;
 	
-	cliprange_t*		start;
-
 	// Find the corners of the box
 	// that define the edges from current viewpoint.
 	if (ViewPos.X <= bspcoord[BOXLEFT])
@@ -911,21 +767,7 @@ static bool R_CheckBBox (float *bspcoord)	// killough 1/28/98: static
 	// Find the first clippost that touches the source post
 	//	(adjacent pixels are touching).
 
-	// Does not cross a pixel.
-	if (sx2 <= sx1)
-		return false;
-
-	start = solidsegs;
-	while (start->last < sx2)
-		start++;
-
-	if (sx1 >= start->first && sx2 <= start->last)
-	{
-		// The clippost contains the new span.
-		return false;
-	}
-
-	return true;
+	return R_IsWallSegmentVisible(sx1, sx2);
 }
 
 
diff --git a/src/swrenderer/scene/r_clip_segment.cpp b/src/swrenderer/scene/r_clip_segment.cpp
index 1c4da9214..4db069a49 100644
--- a/src/swrenderer/scene/r_clip_segment.cpp
+++ b/src/swrenderer/scene/r_clip_segment.cpp
@@ -26,8 +26,16 @@
 
 namespace swrenderer
 {
-	cliprange_t *newend;
-	cliprange_t solidsegs[MAXWIDTH/2+2];
+	namespace
+	{
+		struct cliprange_t
+		{
+			short first, last;
+		};
+
+		cliprange_t *newend; // newend is one past the last valid seg
+		cliprange_t solidsegs[MAXWIDTH / 2 + 2];
+	}
 
 	void R_ClearClipSegs(short left, short right)
 	{
@@ -37,4 +45,145 @@ namespace swrenderer
 		solidsegs[1].last = 0x7fff;
 		newend = solidsegs+2;
 	}
+
+	bool R_CheckClipWallSegment(int first, int last)
+	{
+		cliprange_t *start;
+
+		// Find the first range that touches the range
+		// (adjacent pixels are touching).
+		start = solidsegs;
+		while (start->last < first)
+			start++;
+
+		if (first < start->first)
+		{
+			return true;
+		}
+
+		// Bottom contained in start?
+		if (last > start->last)
+		{
+			return true;
+		}
+
+		return false;
+	}
+
+	bool R_IsWallSegmentVisible(int sx1, int sx2)
+	{
+		// Does not cross a pixel.
+		if (sx2 <= sx1)
+			return false;
+
+		cliprange_t *start = solidsegs;
+		while (start->last < sx2)
+			start++;
+
+		if (sx1 >= start->first && sx2 <= start->last)
+		{
+			// The clippost contains the new span.
+			return false;
+		}
+
+		return true;
+	}
+
+	bool R_ClipWallSegment(int first, int last, bool solid, VisibleSegmentCallback callback)
+	{
+		cliprange_t *next, *start;
+		int i, j;
+		bool res = false;
+
+		// Find the first range that touches the range
+		// (adjacent pixels are touching).
+		start = solidsegs;
+		while (start->last < first)
+			start++;
+
+		if (first < start->first)
+		{
+			res = true;
+			if (last <= start->first)
+			{
+				// Post is entirely visible (above start).
+				if (!callback(first, last))
+					return true;
+
+				// Insert a new clippost for solid walls.
+				if (solid)
+				{
+					if (last == start->first)
+					{
+						start->first = first;
+					}
+					else
+					{
+						next = newend;
+						newend++;
+						while (next != start)
+						{
+							*next = *(next - 1);
+							next--;
+						}
+						next->first = first;
+						next->last = last;
+					}
+				}
+				return true;
+			}
+
+			// There is a fragment above *start.
+			if (!callback(first, start->first) && solid)
+			{
+				start->first = first;
+			}
+		}
+
+		// Bottom contained in start?
+		if (last <= start->last)
+			return res;
+
+		bool clipsegment;
+		next = start;
+		while (last >= (next + 1)->first)
+		{
+			// There is a fragment between two posts.
+			clipsegment = callback(next->last, (next + 1)->first);
+			next++;
+
+			if (last <= next->last)
+			{
+				// Bottom is contained in next.
+				last = next->last;
+				goto crunch;
+			}
+		}
+
+		// There is a fragment after *next.
+		clipsegment = callback(next->last, last);
+
+	crunch:
+		if (!clipsegment)
+		{
+			return true;
+		}
+		if (solid)
+		{
+			// Adjust the clip size.
+			start->last = last;
+
+			if (next != start)
+			{
+				// Remove start+1 to next from the clip list,
+				// because start now covers their area.
+				for (i = 1, j = (int)(newend - next); j > 0; i++, j--)
+				{
+					start[i] = next[i];
+				}
+				newend = start + i;
+			}
+		}
+		return true;
+	}
 }
diff --git a/src/swrenderer/scene/r_clip_segment.h b/src/swrenderer/scene/r_clip_segment.h
index ce6fffe07..3ebe464d8 100644
--- a/src/swrenderer/scene/r_clip_segment.h
+++ b/src/swrenderer/scene/r_clip_segment.h
@@ -3,14 +3,10 @@
 
 namespace swrenderer
 {
-	struct cliprange_t
-	{
-		short first, last;
-	};
-	
-	// newend is one past the last valid seg
-	extern cliprange_t *newend;
-	extern cliprange_t solidsegs[MAXWIDTH/2+2];
-	
+	typedef bool(*VisibleSegmentCallback)(int x1, int x2);
+
 	void R_ClearClipSegs(short left, short right);
+	bool R_ClipWallSegment(int x1, int x2, bool solid, VisibleSegmentCallback callback);
+	bool R_CheckClipWallSegment(int first, int last);
+	bool R_IsWallSegmentVisible(int x1, int x2);
 }
diff --git a/src/swrenderer/scene/r_segs.cpp b/src/swrenderer/scene/r_segs.cpp
index 5be89ecb0..f23a9326b 100644
--- a/src/swrenderer/scene/r_segs.cpp
+++ b/src/swrenderer/scene/r_segs.cpp
@@ -1587,7 +1587,7 @@ ptrdiff_t R_NewOpening (ptrdiff_t len)
 // A wall segment will be drawn between start and stop pixels (inclusive).
 //
 
-void R_StoreWallRange (int start, int stop)
+bool R_StoreWallRange (int start, int stop)
 {
 	int i;
 	bool maskedtexture = false;
@@ -1827,7 +1827,8 @@ void R_StoreWallRange (int start, int stop)
 
 	if(fake3D & 7) {
 		ds_p++;
-		return;
+
+		return !(fake3D & FAKE3D_FAKEMASK);
 	}
 
 	// save sprite clipping info
@@ -1888,6 +1889,8 @@ void R_StoreWallRange (int start, int stop)
 	}
 
 	ds_p++;
+
+	return !(fake3D & FAKE3D_FAKEMASK);
 }
 
 int R_CreateWallSegmentY(short *outbuf, double z1, double z2, const FWallCoords *wallc)
diff --git a/src/swrenderer/scene/r_segs.h b/src/swrenderer/scene/r_segs.h
index 20cba123b..f9b235872 100644
--- a/src/swrenderer/scene/r_segs.h
+++ b/src/swrenderer/scene/r_segs.h
@@ -28,6 +28,7 @@ namespace swrenderer
 
 struct drawseg_t;
 
+bool R_StoreWallRange(int start, int stop);
 void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2);
 
 extern short *openings;