diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 9c1a95c9316626ce5f02747eaba356b60368ee62..8c4651c040a174328d5ca4bc7aaee5f12f512233 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -1034,6 +1034,191 @@ static boolean HWR_BlendMidtextureSurface(FSurfaceInfo *pSurf)
 	return true;
 }
 
+static void HWR_RenderMidtexture(INT32 gl_midtexture, float cliplow, float cliphigh, fixed_t worldtop, fixed_t worldbottom, fixed_t worldhigh, fixed_t worldlow, fixed_t worldtopslope, fixed_t worldbottomslope, fixed_t worldhighslope, fixed_t worldlowslope, UINT32 lightnum, FOutVector *inWallVerts)
+{
+	FOutVector wallVerts[4];
+
+	FSurfaceInfo Surf;
+	Surf.PolyColor.s.alpha = 255;
+
+	// Determine if it's visible
+	if (!HWR_BlendMidtextureSurface(&Surf))
+		return;
+
+	fixed_t texheight = FixedDiv(textureheight[gl_midtexture], abs(gl_sidedef->scaley_mid));
+	INT32 repeats;
+
+	if (gl_sidedef->repeatcnt)
+		repeats = 1 + gl_sidedef->repeatcnt;
+	else if (gl_linedef->flags & ML_WRAPMIDTEX)
+	{
+		fixed_t high, low;
+
+		if (gl_frontsector->ceilingheight > gl_backsector->ceilingheight)
+			high = gl_backsector->ceilingheight;
+		else
+			high = gl_frontsector->ceilingheight;
+
+		if (gl_frontsector->floorheight > gl_backsector->floorheight)
+			low = gl_frontsector->floorheight;
+		else
+			low = gl_backsector->floorheight;
+
+		repeats = (high - low) / texheight;
+		if ((high - low) % texheight)
+			repeats++; // tile an extra time to fill the gap -- Monster Iestyn
+	}
+	else
+		repeats = 1;
+
+	GLMapTexture_t *grTex = HWR_GetTexture(gl_midtexture);
+	float xscale = FixedToFloat(gl_sidedef->scalex_mid);
+	float yscale = FixedToFloat(gl_sidedef->scaley_mid);
+
+	// SoM: a little note: popentop and popenbottom
+	// record the limits the texture can be displayed in.
+	// polytop and polybottom, are the ideal (i.e. unclipped)
+	// heights of the polygon, and h & l, are the final (clipped)
+	// poly coords.
+	fixed_t popentop, popenbottom, polytop, polybottom, lowcut, highcut;
+	fixed_t popentopslope, popenbottomslope, polytopslope, polybottomslope, lowcutslope, highcutslope;
+
+	// NOTE: With polyobjects, whenever you need to check the properties of the polyobject sector it belongs to,
+	// you must use the linedef's backsector to be correct
+	// From CB
+	if (gl_curline->polyseg)
+	{
+		// Change this when polyobjects support slopes
+		popentop = popentopslope = gl_curline->backsector->ceilingheight;
+		popenbottom = popenbottomslope = gl_curline->backsector->floorheight;
+	}
+	else
+	{
+		popentop = min(worldtop, worldhigh);
+		popenbottom = max(worldbottom, worldlow);
+		popentopslope = min(worldtopslope, worldhighslope);
+		popenbottomslope = max(worldbottomslope, worldlowslope);
+	}
+
+	// Find the wall's coordinates
+	fixed_t midtexheight = texheight * repeats;
+
+	fixed_t rowoffset = FixedDiv(gl_sidedef->rowoffset + gl_sidedef->offsety_mid, abs(gl_sidedef->scaley_mid));
+
+	// Texture is not skewed
+	if (gl_linedef->flags & ML_NOSKEW)
+	{
+		// Peg it to the floor
+		if (gl_linedef->flags & ML_MIDPEG)
+		{
+			polybottom = max(gl_frontsector->floorheight, gl_backsector->floorheight) + rowoffset;
+			polytop = polybottom + midtexheight;
+		}
+		// Peg it to the ceiling
+		else
+		{
+			polytop = min(gl_frontsector->ceilingheight, gl_backsector->ceilingheight) + rowoffset;
+			polybottom = polytop - midtexheight;
+		}
+
+		// The right side's coordinates are the the same as the left side
+		polytopslope = polytop;
+		polybottomslope = polybottom;
+	}
+	// Skew the texture, but peg it to the floor
+	else if (gl_linedef->flags & ML_MIDPEG)
+	{
+		polybottom = popenbottom + rowoffset;
+		polytop = polybottom + midtexheight;
+		polybottomslope = popenbottomslope + rowoffset;
+		polytopslope = polybottomslope + midtexheight;
+	}
+	// Skew it according to the ceiling's slope
+	else
+	{
+		polytop = popentop + rowoffset;
+		polybottom = polytop - midtexheight;
+		polytopslope = popentopslope + rowoffset;
+		polybottomslope = polytopslope - midtexheight;
+	}
+
+	// The cut-off values of a linedef can always be constant, since every line has an absoulute front and or back sector
+	if (gl_curline->polyseg)
+	{
+		lowcut = polybottom;
+		highcut = polytop;
+		lowcutslope = polybottomslope;
+		highcutslope = polytopslope;
+	}
+	else
+	{
+		lowcut = popenbottom;
+		highcut = popentop;
+		lowcutslope = popenbottomslope;
+		highcutslope = popentopslope;
+	}
+
+	fixed_t h = min(highcut, polytop);
+	fixed_t l = max(polybottom, lowcut);
+	fixed_t hS = min(highcutslope, polytopslope);
+	fixed_t lS = max(polybottomslope, lowcutslope);
+
+	// PEGGING
+	fixed_t texturevpeg, texturevpegslope;
+
+	if (gl_linedef->flags & ML_MIDPEG)
+	{
+		texturevpeg = midtexheight - h + polybottom;
+		texturevpegslope = midtexheight - hS + polybottomslope;
+	}
+	else
+	{
+		texturevpeg = polytop - h;
+		texturevpegslope = polytopslope - hS;
+	}
+
+	memcpy(wallVerts, inWallVerts, sizeof(wallVerts));
+
+	// Left side
+	wallVerts[3].t = texturevpeg * yscale * grTex->scaleY;
+	wallVerts[0].t = (h - l + texturevpeg) * yscale * grTex->scaleY;
+	wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->textureoffset + gl_sidedef->offsetx_mid) * grTex->scaleX;
+
+	// Right side
+	wallVerts[2].t = texturevpegslope * yscale * grTex->scaleY;
+	wallVerts[1].t = (hS - lS + texturevpegslope) * yscale * grTex->scaleY;
+	wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->textureoffset + gl_sidedef->offsetx_mid) * grTex->scaleX;
+
+	// set top/bottom coords
+	// Take the texture peg into account, rather than changing the offsets past
+	// where the polygon might not be.
+	wallVerts[3].y = FIXED_TO_FLOAT(h);
+	wallVerts[0].y = FIXED_TO_FLOAT(l);
+	wallVerts[2].y = FIXED_TO_FLOAT(hS);
+	wallVerts[1].y = FIXED_TO_FLOAT(lS);
+
+	// TODO: Actually use the surface's flags so that I don't have to do this
+	FUINT blendmode = Surf.PolyFlags;
+
+	// Render midtextures on two-sided lines with a z-buffer offset.
+	// This will cause the midtexture appear on top, if a FOF overlaps with it.
+	blendmode |= PF_Decal;
+
+	extracolormap_t *colormap = gl_frontsector->extra_colormap;
+
+	if (gl_frontsector->numlights)
+	{
+		if (!(blendmode & PF_Masked))
+			HWR_SplitWall(gl_frontsector, wallVerts, gl_midtexture, &Surf, FOF_TRANSLUCENT, NULL, blendmode);
+		else
+			HWR_SplitWall(gl_frontsector, wallVerts, gl_midtexture, &Surf, FOF_CUTLEVEL, NULL, blendmode);
+	}
+	else if (!(blendmode & PF_Masked))
+		HWR_AddTransparentWall(wallVerts, &Surf, gl_midtexture, blendmode, false, lightnum, colormap);
+	else
+		HWR_ProjectWall(wallVerts, &Surf, blendmode, lightnum, colormap);
+}
+
 //
 // HWR_ProcessSeg
 // A portion or all of a wall segment will be drawn, from startfrac to endfrac,
@@ -1105,9 +1290,8 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 	wallVerts[2].z = wallVerts[1].z = ve.y;
 
 	// x offset the texture
-	fixed_t texturehpeg = gl_sidedef->textureoffset + gl_curline->offset;
-	float cliplow = (float)texturehpeg;
-	float cliphigh = (float)(texturehpeg + (gl_curline->flength*FRACUNIT));
+	float cliplow = (float)gl_curline->offset;
+	float cliphigh = cliplow + (gl_curline->flength * FRACUNIT);
 
 	FUINT lightnum = HWR_CalcWallLight(gl_frontsector->lightlevel, vs.x, vs.y, ve.x, ve.y);
 	extracolormap_t *colormap = gl_frontsector->extra_colormap;
@@ -1122,6 +1306,7 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 	if (gl_backsector)
 	{
 		INT32 gl_toptexture = 0, gl_bottomtexture = 0;
+
 		fixed_t texturevpeg;
 
 		SLOPEPARAMS(gl_backsector->c_slope, worldhigh, worldhighslope, gl_backsector->ceilingheight)
@@ -1151,30 +1336,46 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 		if ((worldhighslope < worldtopslope || worldhigh < worldtop) && gl_toptexture)
 		{
 			grTex = HWR_GetTexture(gl_toptexture);
-			xscale = FixedToFloat(gl_sidedef->scalex_top);
-			yscale = FixedToFloat(gl_sidedef->scaley_top);
+			xscale = FixedToFloat(abs(gl_sidedef->scalex_top));
+			yscale = FixedToFloat(abs(gl_sidedef->scaley_top));
 
-			fixed_t texheight = FixedDiv(textureheight[gl_toptexture], gl_sidedef->scaley_top);
+			fixed_t offsetx_top = gl_sidedef->textureoffset + gl_sidedef->offsetx_top;
+
+			float left = cliplow * xscale;
+			float right = cliphigh * xscale;
+			if (gl_sidedef->scalex_top < 0)
+			{
+				left = -left;
+				right = -right;
+				offsetx_top = -offsetx_top;
+			}
+
+			fixed_t texheight = textureheight[gl_toptexture];
+			fixed_t texheightscaled = FixedDiv(texheight, abs(gl_sidedef->scaley_top));
 
 			// PEGGING
+			// FIXME: This is probably not correct?
 			if (gl_linedef->flags & ML_DONTPEGTOP)
 				texturevpeg = 0;
 			else if (gl_linedef->flags & ML_SKEWTD)
 				texturevpeg = worldhigh + texheight - worldtop;
 			else
-				texturevpeg = gl_backsector->ceilingheight + texheight - gl_frontsector->ceilingheight;
+				texturevpeg = gl_backsector->ceilingheight + texheightscaled - gl_frontsector->ceilingheight;
 
 			texturevpeg *= yscale;
 
-			texturevpeg += gl_sidedef->rowoffset + gl_sidedef->offsety_top;
+			if (gl_sidedef->scaley_top < 0)
+				texturevpeg -= gl_sidedef->rowoffset + gl_sidedef->offsety_top;
+			else
+				texturevpeg += gl_sidedef->rowoffset + gl_sidedef->offsety_top;
 
 			// This is so that it doesn't overflow and screw up the wall, it doesn't need to go higher than the texture's height anyway
-			texturevpeg %= texheight;
+			texturevpeg %= texheightscaled;
 
 			wallVerts[3].t = wallVerts[2].t = texturevpeg * grTex->scaleY;
 			wallVerts[0].t = wallVerts[1].t = (texturevpeg + (gl_frontsector->ceilingheight - gl_backsector->ceilingheight) * yscale) * grTex->scaleY;
-			wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->offsetx_top) * grTex->scaleX;
-			wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->offsetx_top) * grTex->scaleX;
+			wallVerts[0].s = wallVerts[3].s = (left + offsetx_top) * grTex->scaleX;
+			wallVerts[2].s = wallVerts[1].s = (right + offsetx_top) * grTex->scaleX;
 
 			// Adjust t value for sloped walls
 			if (!(gl_linedef->flags & ML_SKEWTD))
@@ -1199,6 +1400,14 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				wallVerts[2].t = wallVerts[1].t - (worldtopslope - worldhighslope) * yscale * grTex->scaleY;
 			}
 
+			if (gl_sidedef->scaley_top < 0)
+			{
+				wallVerts[0].t = -wallVerts[0].t;
+				wallVerts[1].t = -wallVerts[1].t;
+				wallVerts[2].t = -wallVerts[2].t;
+				wallVerts[3].t = -wallVerts[3].t;
+			}
+
 			// set top/bottom coords
 			wallVerts[3].y = FIXED_TO_FLOAT(worldtop);
 			wallVerts[0].y = FIXED_TO_FLOAT(worldhigh);
@@ -1217,8 +1426,19 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 		if ((worldlowslope > worldbottomslope || worldlow > worldbottom) && gl_bottomtexture)
 		{
 			grTex = HWR_GetTexture(gl_bottomtexture);
-			xscale = FixedToFloat(gl_sidedef->scalex_bottom);
-			yscale = FixedToFloat(gl_sidedef->scaley_bottom);
+			xscale = FixedToFloat(abs(gl_sidedef->scalex_bottom));
+			yscale = FixedToFloat(abs(gl_sidedef->scaley_bottom));
+
+			fixed_t offsetx_bottom = gl_sidedef->textureoffset + gl_sidedef->offsetx_bottom;
+
+			float left = cliplow * xscale;
+			float right = cliphigh * xscale;
+			if (gl_sidedef->scalex_bottom < 0)
+			{
+				left = -left;
+				right = -right;
+				offsetx_bottom = -offsetx_bottom;
+			}
 
 			// PEGGING
 			if (!(gl_linedef->flags & ML_DONTPEGBOTTOM))
@@ -1230,15 +1450,18 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 
 			texturevpeg *= yscale;
 
-			texturevpeg += gl_sidedef->rowoffset + gl_sidedef->offsety_bottom;
+			if (gl_sidedef->scaley_bottom < 0)
+				texturevpeg -= gl_sidedef->rowoffset + gl_sidedef->offsety_bottom;
+			else
+				texturevpeg += gl_sidedef->rowoffset + gl_sidedef->offsety_bottom;
 
 			// This is so that it doesn't overflow and screw up the wall, it doesn't need to go higher than the texture's height anyway
-			texturevpeg %= FixedDiv(textureheight[gl_bottomtexture], gl_sidedef->scaley_bottom);
+			texturevpeg %= FixedDiv(textureheight[gl_bottomtexture], abs(gl_sidedef->scaley_bottom));
 
 			wallVerts[3].t = wallVerts[2].t = texturevpeg * grTex->scaleY;
 			wallVerts[0].t = wallVerts[1].t = (texturevpeg + (gl_backsector->floorheight - gl_frontsector->floorheight) * yscale) * grTex->scaleY;
-			wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->offsetx_bottom) * grTex->scaleX;
-			wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->offsetx_bottom) * grTex->scaleX;
+			wallVerts[0].s = wallVerts[3].s = (left + offsetx_bottom) * grTex->scaleX;
+			wallVerts[2].s = wallVerts[1].s = (right + offsetx_bottom) * grTex->scaleX;
 
 			// Adjust t value for sloped walls
 			if (!(gl_linedef->flags & ML_SKEWTD))
@@ -1262,6 +1485,14 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				wallVerts[1].t = (texturevpeg + (worldlowslope - worldbottomslope) * yscale) * grTex->scaleY;
 			}
 
+			if (gl_sidedef->scaley_bottom < 0)
+			{
+				wallVerts[0].t = -wallVerts[0].t;
+				wallVerts[1].t = -wallVerts[1].t;
+				wallVerts[2].t = -wallVerts[2].t;
+				wallVerts[3].t = -wallVerts[3].t;
+			}
+
 			// set top/bottom coords
 			wallVerts[3].y = FIXED_TO_FLOAT(worldlow);
 			wallVerts[0].y = FIXED_TO_FLOAT(worldbottom);
@@ -1276,196 +1507,14 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				HWR_ProjectWall(wallVerts, &Surf, PF_Masked, lightnum, colormap);
 		}
 
-		// Render midtexture if there's one. Determine if it's visible first, though
-		if (gl_midtexture && HWR_BlendMidtextureSurface(&Surf))
-		{
-			sector_t *front, *back;
-			fixed_t texheight = FixedDiv(textureheight[gl_midtexture], gl_sidedef->scaley_mid);
-			INT32 repeats;
-
-			if (gl_linedef->frontsector->heightsec != -1)
-				front = &sectors[gl_linedef->frontsector->heightsec];
-			else
-				front = gl_linedef->frontsector;
-
-			if (gl_linedef->backsector->heightsec != -1)
-				back = &sectors[gl_linedef->backsector->heightsec];
-			else
-				back = gl_linedef->backsector;
-
-			if (gl_sidedef->repeatcnt)
-				repeats = 1 + gl_sidedef->repeatcnt;
-			else if (gl_linedef->flags & ML_WRAPMIDTEX)
-			{
-				fixed_t high, low;
-
-				if (front->ceilingheight > back->ceilingheight)
-					high = back->ceilingheight;
-				else
-					high = front->ceilingheight;
-
-				if (front->floorheight > back->floorheight)
-					low = front->floorheight;
-				else
-					low = back->floorheight;
-
-				repeats = (high - low) / texheight;
-				if ((high - low) % texheight)
-					repeats++; // tile an extra time to fill the gap -- Monster Iestyn
-			}
-			else
-				repeats = 1;
-
-			grTex = HWR_GetTexture(gl_midtexture);
-			xscale = FixedToFloat(gl_sidedef->scalex_mid);
-			yscale = FixedToFloat(gl_sidedef->scaley_mid);
-
-			// SoM: a little note: popentop and popenbottom
-			// record the limits the texture can be displayed in.
-			// polytop and polybottom, are the ideal (i.e. unclipped)
-			// heights of the polygon, and h & l, are the final (clipped)
-			// poly coords.
-			fixed_t popentop, popenbottom, polytop, polybottom, lowcut, highcut;
-			fixed_t popentopslope, popenbottomslope, polytopslope, polybottomslope, lowcutslope, highcutslope;
-
-			// NOTE: With polyobjects, whenever you need to check the properties of the polyobject sector it belongs to,
-			// you must use the linedef's backsector to be correct
-			// From CB
-			if (gl_curline->polyseg)
-			{
-				popentop = popentopslope = back->ceilingheight;
-				popenbottom = popenbottomslope = back->floorheight;
-			}
-			else
-			{
-				popentop = min(worldtop, worldhigh);
-				popenbottom = max(worldbottom, worldlow);
-				popentopslope = min(worldtopslope, worldhighslope);
-				popenbottomslope = max(worldbottomslope, worldlowslope);
-			}
-
-			// Find the wall's coordinates
-			fixed_t midtexheight = texheight * repeats;
-
-			fixed_t rowoffset = FixedDiv(gl_sidedef->rowoffset + gl_sidedef->offsety_mid, gl_sidedef->scaley_mid);
-
-			// Texture is not skewed
-			if (gl_linedef->flags & ML_NOSKEW)
-			{
-				// Peg it to the floor
-				if (gl_linedef->flags & ML_MIDPEG)
-				{
-					polybottom = max(front->floorheight, back->floorheight) + rowoffset;
-					polytop = polybottom + midtexheight;
-				}
-				// Peg it to the ceiling
-				else
-				{
-					polytop = min(front->ceilingheight, back->ceilingheight) + rowoffset;
-					polybottom = polytop - midtexheight;
-				}
-
-				// The right side's coordinates are the the same as the left side
-				polytopslope = polytop;
-				polybottomslope = polybottom;
-			}
-			// Skew the texture, but peg it to the floor
-			else if (gl_linedef->flags & ML_MIDPEG)
-			{
-				polybottom = popenbottom + rowoffset;
-				polytop = polybottom + midtexheight;
-				polybottomslope = popenbottomslope + rowoffset;
-				polytopslope = polybottomslope + midtexheight;
-			}
-			// Skew it according to the ceiling's slope
-			else
-			{
-				polytop = popentop + rowoffset;
-				polybottom = polytop - midtexheight;
-				polytopslope = popentopslope + rowoffset;
-				polybottomslope = polytopslope - midtexheight;
-			}
-
-			// CB
-			// NOTE: With polyobjects, whenever you need to check the properties of the polyobject sector it belongs to,
-			// you must use the linedef's backsector to be correct
-			if (gl_curline->polyseg)
-			{
-				lowcut = polybottom;
-				highcut = polytop;
-				lowcutslope = polybottomslope;
-				highcutslope = polytopslope;
-			}
-			else
-			{
-				// The cut-off values of a linedef can always be constant, since every line has an absoulute front and or back sector
-				lowcut = popenbottom;
-				highcut = popentop;
-				lowcutslope = popenbottomslope;
-				highcutslope = popentopslope;
-			}
-
-			h = min(highcut, polytop);
-			l = max(polybottom, lowcut);
-			hS = min(highcutslope, polytopslope);
-			lS = max(polybottomslope, lowcutslope);
-
-			// PEGGING
-			fixed_t texturevpegslope;
-
-			if (gl_linedef->flags & ML_MIDPEG)
-			{
-				texturevpeg = midtexheight - h + polybottom;
-				texturevpegslope = midtexheight - hS + polybottomslope;
-			}
-			else
-			{
-				texturevpeg = polytop - h;
-				texturevpegslope = polytopslope - hS;
-			}
-
-			// Left side
-			wallVerts[3].t = texturevpeg * yscale * grTex->scaleY;
-			wallVerts[0].t = (h - l + texturevpeg) * yscale * grTex->scaleY;
-			wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->offsetx_mid) * grTex->scaleX;
-
-			// Right side
-			wallVerts[2].t = texturevpegslope * yscale * grTex->scaleY;
-			wallVerts[1].t = (hS - lS + texturevpegslope) * yscale * grTex->scaleY;
-			wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->offsetx_mid) * grTex->scaleX;
-
-			// set top/bottom coords
-			// Take the texture peg into account, rather than changing the offsets past
-			// where the polygon might not be.
-			wallVerts[3].y = FIXED_TO_FLOAT(h);
-			wallVerts[0].y = FIXED_TO_FLOAT(l);
-			wallVerts[2].y = FIXED_TO_FLOAT(hS);
-			wallVerts[1].y = FIXED_TO_FLOAT(lS);
-
-			// TODO: Actually use the surface's flags so that I don't have to do this
-			FUINT blendmode = Surf.PolyFlags;
-
-			// Render midtextures on two-sided lines with a z-buffer offset.
-			// This will cause the midtexture appear on top, if a FOF overlaps with it.
-			blendmode |= PF_Decal;
-
-			if (gl_frontsector->numlights)
-			{
-				if (!(blendmode & PF_Masked))
-					HWR_SplitWall(gl_frontsector, wallVerts, gl_midtexture, &Surf, FOF_TRANSLUCENT, NULL, blendmode);
-				else
-					HWR_SplitWall(gl_frontsector, wallVerts, gl_midtexture, &Surf, FOF_CUTLEVEL, NULL, blendmode);
-			}
-			else if (!(blendmode & PF_Masked))
-				HWR_AddTransparentWall(wallVerts, &Surf, gl_midtexture, blendmode, false, lightnum, colormap);
-			else
-				HWR_ProjectWall(wallVerts, &Surf, blendmode, lightnum, colormap);
-		}
+		// Render midtexture if there's one
+		if (gl_midtexture)
+			HWR_RenderMidtexture(gl_midtexture, cliplow, cliphigh, worldtop, worldbottom, worldhigh, worldlow, worldtopslope, worldbottomslope, worldhighslope, worldlowslope, lightnum, wallVerts);
 
-		// Sky culling
-		// No longer so much a mess as before!
 		if (!gl_curline->polyseg) // Don't do it for polyobjects
 		{
+			// Sky culling
+			// No longer so much a mess as before!
 			if (gl_frontsector->ceilingpic == skyflatnum
 				&& gl_backsector->ceilingpic != skyflatnum) // don't cull if back sector is also sky
 			{
@@ -1509,8 +1558,8 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 
 			wallVerts[3].t = wallVerts[2].t = texturevpeg * grTex->scaleY;
 			wallVerts[0].t = wallVerts[1].t = (texturevpeg + gl_frontsector->ceilingheight - gl_frontsector->floorheight) * grTex->scaleY;
-			wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->offsetx_mid) * grTex->scaleX;
-			wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->offsetx_mid) * grTex->scaleX;
+			wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + gl_sidedef->textureoffset + gl_sidedef->offsetx_mid) * grTex->scaleX;
+			wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + gl_sidedef->textureoffset + gl_sidedef->offsetx_mid) * grTex->scaleX;
 
 			// Texture correction for slopes
 			if (gl_linedef->flags & ML_NOSKEW) {
@@ -1573,8 +1622,9 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 		// Used for height comparisons and etc across FOFs and slopes
 		fixed_t high1, highslope1, low1, lowslope1;
 
+		fixed_t texturehpeg = gl_sidedef->textureoffset + gl_sidedef->offsetx_mid;
+
 		INT32 texnum;
-		line_t * newline = NULL; // Multi-Property FOF
 
 		lowcut = max(worldbottom, worldlow);
 		highcut = min(worldtop, worldhigh);
@@ -1608,16 +1658,14 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				if ((high1 < lowcut && highslope1 < lowcutslope) || (low1 > highcut && lowslope1 > highcutslope))
 					continue;
 
-				side_t *side = &sides[rover->master->sidenum[0]];
+				side_t *side = R_GetFFloorSide(gl_curline, rover);
 
 				boolean do_texture_skew;
 				boolean dont_peg_bottom;
 
 				if (rover->master->flags & ML_TFERLINE)
 				{
-					size_t linenum = gl_curline->linedef-gl_backsector->lines[0];
-					newline = rover->master->frontsector->lines[0] + linenum;
-					side = &sides[newline->sidenum[0]];
+					line_t *newline = R_GetFFloorLine(gl_curline, rover);
 					do_texture_skew = newline->flags & ML_SKEWTD;
 					dont_peg_bottom = newline->flags & ML_DONTPEGBOTTOM;
 				}
@@ -1695,14 +1743,14 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 						}
 					}
 
-					wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + side->offsetx_mid) * grTex->scaleX;
-					wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + side->offsetx_mid) * grTex->scaleX;
+					wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + texturehpeg + side->offsetx_mid) * grTex->scaleX;
+					wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + texturehpeg + side->offsetx_mid) * grTex->scaleX;
 				}
 
+				FBITFIELD blendmode;
+
 				if (rover->fofflags & FOF_FOG)
 				{
-					FBITFIELD blendmode;
-
 					blendmode = PF_Fog|PF_NoTexture;
 
 					lightnum = HWR_CalcWallLight(rover->master->frontsector->lightlevel, vs.x, vs.y, ve.x, ve.y);
@@ -1717,7 +1765,7 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				}
 				else
 				{
-					FBITFIELD blendmode = PF_Masked;
+					blendmode = PF_Masked;
 
 					if ((rover->fofflags & FOF_TRANSLUCENT && !(rover->fofflags & FOF_SPLAT)) || rover->blend)
 					{
@@ -1765,13 +1813,21 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				if ((high1 < lowcut && highslope1 < lowcutslope) || (low1 > highcut && lowslope1 > highcutslope))
 					continue;
 
-				side_t *side = &sides[rover->master->sidenum[0]];
+				side_t *side = R_GetFFloorSide(gl_curline, rover);
+
+				boolean do_texture_skew;
+				boolean dont_peg_bottom;
 
 				if (rover->master->flags & ML_TFERLINE)
 				{
-					size_t linenum = gl_curline->linedef-gl_backsector->lines[0];
-					newline = rover->master->frontsector->lines[0] + linenum;
-					side = &sides[newline->sidenum[0]];
+					line_t *newline = R_GetFFloorLine(gl_curline, rover);
+					do_texture_skew = newline->flags & ML_SKEWTD;
+					dont_peg_bottom = newline->flags & ML_DONTPEGBOTTOM;
+				}
+				else
+				{
+					do_texture_skew = rover->master->flags & ML_SKEWTD;
+					dont_peg_bottom = gl_curline->linedef->flags & ML_DONTPEGBOTTOM;
 				}
 
 				texnum = R_GetTextureNum(side->midtexture);
@@ -1808,23 +1864,49 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				}
 				else
 				{
+					// Wow, how was this missing from OpenGL for so long?
+					// ...Oh well, anyway, Lower Unpegged now changes pegging of FOFs like in software
+					// -- Monster Iestyn 26/06/18
+					fixed_t texturevpeg = side->rowoffset + side->offsety_mid;
+
 					grTex = HWR_GetTexture(texnum);
 					xscale = FixedToFloat(side->scalex_mid);
 					yscale = FixedToFloat(side->scaley_mid);
 
-					fixed_t diff = (*rover->topheight - h) * yscale;
+					if (!do_texture_skew) // no skewing
+					{
+						if (dont_peg_bottom)
+							texturevpeg -= (*rover->topheight - *rover->bottomheight) * yscale;
 
-					wallVerts[3].t = wallVerts[2].t = (diff + side->rowoffset + side->offsety_mid) * grTex->scaleY;
-					wallVerts[0].t = wallVerts[1].t = (((h - l) * yscale) + (diff + side->rowoffset + side->offsety_mid)) * grTex->scaleY;
+						wallVerts[3].t = (((*rover->topheight - h) * yscale) + texturevpeg) * grTex->scaleY;
+						wallVerts[2].t = (((*rover->topheight - hS) * yscale) + texturevpeg) * grTex->scaleY;
+						wallVerts[0].t = (((*rover->topheight - l) * yscale) + texturevpeg) * grTex->scaleY;
+						wallVerts[1].t = (((*rover->topheight - lS) * yscale) + texturevpeg) * grTex->scaleY;
+					}
+					else
+					{
+						if (!dont_peg_bottom) // skew by top
+						{
+							wallVerts[3].t = wallVerts[2].t = texturevpeg * grTex->scaleY;
+							wallVerts[0].t = (((h - l) * yscale) + texturevpeg) * grTex->scaleY;
+							wallVerts[1].t = (((hS - lS) * yscale) + texturevpeg) * grTex->scaleY;
+						}
+						else // skew by bottom
+						{
+							wallVerts[0].t = wallVerts[1].t = texturevpeg * grTex->scaleY;
+							wallVerts[3].t = wallVerts[0].t - ((h - l) * yscale) * grTex->scaleY;
+							wallVerts[2].t = wallVerts[1].t - ((hS - lS) * yscale) * grTex->scaleY;
+						}
+					}
 
-					wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + side->offsetx_mid) * grTex->scaleX;
-					wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + side->offsetx_mid) * grTex->scaleX;
+					wallVerts[0].s = wallVerts[3].s = ((cliplow * xscale) + texturehpeg + side->offsetx_mid) * grTex->scaleX;
+					wallVerts[2].s = wallVerts[1].s = ((cliphigh * xscale) + texturehpeg + side->offsetx_mid) * grTex->scaleX;
 				}
 
+				FBITFIELD blendmode;
+
 				if (rover->fofflags & FOF_FOG)
 				{
-					FBITFIELD blendmode;
-
 					blendmode = PF_Fog|PF_NoTexture;
 
 					lightnum = HWR_CalcWallLight(rover->master->frontsector->lightlevel, vs.x, vs.y, ve.x, ve.y);
@@ -1839,7 +1921,7 @@ static void HWR_ProcessSeg(void) // Sort of like GLWall::Process in GZDoom
 				}
 				else
 				{
-					FBITFIELD blendmode = PF_Masked;
+					blendmode = PF_Masked;
 
 					if ((rover->fofflags & FOF_TRANSLUCENT && !(rover->fofflags & FOF_SPLAT)) || rover->blend)
 					{
@@ -2656,36 +2738,14 @@ static boolean HWR_CheckBBox(fixed_t *bspcoord)
 static inline void HWR_AddPolyObjectSegs(void)
 {
 	size_t i, j;
-	seg_t *gl_fakeline = Z_Calloc(sizeof(seg_t), PU_STATIC, NULL);
-	polyvertex_t *pv1 = Z_Calloc(sizeof(polyvertex_t), PU_STATIC, NULL);
-	polyvertex_t *pv2 = Z_Calloc(sizeof(polyvertex_t), PU_STATIC, NULL);
 
 	// Sort through all the polyobjects
 	for (i = 0; i < numpolys; ++i)
 	{
 		// Render the polyobject's lines
 		for (j = 0; j < po_ptrs[i]->segCount; ++j)
-		{
-			// Copy the info of a polyobject's seg, then convert it to OpenGL floating point
-			M_Memcpy(gl_fakeline, po_ptrs[i]->segs[j], sizeof(seg_t));
-
-			// Now convert the line to float and add it to be rendered
-			pv1->x = FIXED_TO_FLOAT(gl_fakeline->v1->x);
-			pv1->y = FIXED_TO_FLOAT(gl_fakeline->v1->y);
-			pv2->x = FIXED_TO_FLOAT(gl_fakeline->v2->x);
-			pv2->y = FIXED_TO_FLOAT(gl_fakeline->v2->y);
-
-			gl_fakeline->pv1 = pv1;
-			gl_fakeline->pv2 = pv2;
-
-			HWR_AddLine(gl_fakeline);
-		}
+			HWR_AddLine(po_ptrs[i]->segs[j]);
 	}
-
-	// Free temporary data no longer needed
-	Z_Free(pv2);
-	Z_Free(pv1);
-	Z_Free(gl_fakeline);
 }
 
 static void HWR_RenderPolyObjectPlane(polyobj_t *polysector, boolean isceiling, fixed_t fixedheight,
diff --git a/src/p_setup.c b/src/p_setup.c
index 1d985beb4f07399a40607f1ec8f32f480df0e65c..3bde51c3b9091611e5c14f8bae33f6654c7bf198 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3290,8 +3290,6 @@ static void P_InitializeSeg(seg_t *seg)
 	seg->lightmaps = NULL; // list of static lightmap for this seg
 #endif
 
-	seg->numlights = 0;
-	seg->rlights = NULL;
 	seg->polyseg = NULL;
 	seg->dontrenderme = false;
 }
diff --git a/src/r_defs.h b/src/r_defs.h
index d556b540f8a68794986e04da72c58e6d7af8f9a2..899d6ad73fd1bb9ef2b03992e636bf08fa0b42c0 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -742,9 +742,6 @@ typedef struct seg_s
 	lightmap_t *lightmaps; // for static lightmap
 #endif
 
-	// Why slow things down by calculating lightlists for every thick side?
-	size_t numlights;
-	r_lightlist_t *rlights;
 	polyobj_t *polyseg;
 	boolean dontrenderme;
 	boolean glseg;
@@ -828,6 +825,7 @@ typedef struct drawseg_s
 	INT16 *sprtopclip;
 	INT16 *sprbottomclip;
 	fixed_t *maskedtexturecol;
+	fixed_t *maskedtextureheight; // For handling sloped midtextures
 	fixed_t *invscale;
 
 	struct visplane_s *ffloorplanes[MAXFFLOORS];
@@ -839,8 +837,6 @@ typedef struct drawseg_s
 
 	UINT8 portalpass; // if > 0 and <= portalrender, do not affect sprite clipping
 
-	fixed_t maskedtextureheight[MAXVIDWIDTH]; // For handling sloped midtextures
-
 	vertex_t leftpos, rightpos; // Used for rendering FOF walls with slopes
 } drawseg_t;
 
diff --git a/src/r_main.c b/src/r_main.c
index aaab234ad1f168f2df77d2ed55b430b5cc3ff6fa..c920031a053abe7fb0dafb2c0231bcc0ba18d0ae 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -318,7 +318,6 @@ angle_t R_PointToAngle(fixed_t x, fixed_t y)
 }
 
 // This version uses 64-bit variables to avoid overflows with large values.
-// Currently used only by OpenGL rendering.
 angle_t R_PointToAngle64(INT64 x, INT64 y)
 {
 	return (y -= viewy, (x -= viewx) || y) ?
@@ -384,56 +383,26 @@ fixed_t R_PointToDist(fixed_t x, fixed_t y)
 	return R_PointToDist2(viewx, viewy, x, y);
 }
 
-angle_t R_PointToAngleEx(INT32 x2, INT32 y2, INT32 x1, INT32 y1)
+line_t *R_GetFFloorLine(const seg_t *seg, const ffloor_t *pfloor)
 {
-	INT64 dx = x1-x2;
-	INT64 dy = y1-y2;
-	if (dx < INT32_MIN || dx > INT32_MAX || dy < INT32_MIN || dy > INT32_MAX)
+	if (pfloor->master->flags & ML_TFERLINE)
 	{
-		x1 = (int)(dx / 2 + x2);
-		y1 = (int)(dy / 2 + y2);
+		size_t linenum = seg->linedef - pfloor->target->lines[0];
+		return pfloor->master->frontsector->lines[0] + linenum;
 	}
-	return (y1 -= y2, (x1 -= x2) || y1) ?
-	x1 >= 0 ?
-	y1 >= 0 ?
-		(x1 > y1) ? tantoangle[SlopeDivEx(y1,x1)] :                            // octant 0
-		ANGLE_90-tantoangle[SlopeDivEx(x1,y1)] :                               // octant 1
-		x1 > (y1 = -y1) ? 0-tantoangle[SlopeDivEx(y1,x1)] :                    // octant 8
-		ANGLE_270+tantoangle[SlopeDivEx(x1,y1)] :                              // octant 7
-		y1 >= 0 ? (x1 = -x1) > y1 ? ANGLE_180-tantoangle[SlopeDivEx(y1,x1)] :  // octant 3
-		ANGLE_90 + tantoangle[SlopeDivEx(x1,y1)] :                             // octant 2
-		(x1 = -x1) > (y1 = -y1) ? ANGLE_180+tantoangle[SlopeDivEx(y1,x1)] :    // octant 4
-		ANGLE_270-tantoangle[SlopeDivEx(x1,y1)] :                              // octant 5
-		0;
+	else
+		return pfloor->master;
 }
 
-//
-// R_ScaleFromGlobalAngle
-// Returns the texture mapping scale for the current line (horizontal span)
-//  at the given angle.
-// rw_distance must be calculated first.
-//
-// killough 5/2/98: reformatted, cleaned up
-//
-// note: THIS IS USED ONLY FOR WALLS!
-fixed_t R_ScaleFromGlobalAngle(angle_t visangle)
+side_t *R_GetFFloorSide(const seg_t *seg, const ffloor_t *pfloor)
 {
-	angle_t anglea = ANGLE_90 + (visangle-viewangle);
-	angle_t angleb = ANGLE_90 + (visangle-rw_normalangle);
-	fixed_t den = FixedMul(rw_distance, FINESINE(anglea>>ANGLETOFINESHIFT));
-	// proff 11/06/98: Changed for high-res
-	fixed_t num = FixedMul(projectiony, FINESINE(angleb>>ANGLETOFINESHIFT));
-
-	if (den > num>>16)
+	if (pfloor->master->flags & ML_TFERLINE)
 	{
-		num = FixedDiv(num, den);
-		if (num > 64*FRACUNIT)
-			return 64*FRACUNIT;
-		if (num < 256)
-			return 256;
-		return num;
+		line_t *newline = R_GetFFloorLine(seg, pfloor);
+		return &sides[newline->sidenum[0]];
 	}
-	return 64*FRACUNIT;
+	else
+		return &sides[pfloor->master->sidenum[0]];
 }
 
 //
diff --git a/src/r_main.h b/src/r_main.h
index c7dc06c901d417885750238e6424f862ddd9e3d0..da21893286ca6ae1ee934dd6abb9a8c4787689c5 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -77,17 +77,18 @@ INT32 R_PointOnSegSide(fixed_t x, fixed_t y, seg_t *line);
 angle_t R_PointToAngle(fixed_t x, fixed_t y);
 angle_t R_PointToAngle64(INT64 x, INT64 y);
 angle_t R_PointToAngle2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
-angle_t R_PointToAngleEx(INT32 x2, INT32 y2, INT32 x1, INT32 y1);
 fixed_t R_PointToDist(fixed_t x, fixed_t y);
 fixed_t R_PointToDist2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
 
-fixed_t R_ScaleFromGlobalAngle(angle_t visangle);
 boolean R_IsPointInSector(sector_t *sector, fixed_t x, fixed_t y);
 subsector_t *R_PointInSubsector(fixed_t x, fixed_t y);
 subsector_t *R_PointInSubsectorOrNull(fixed_t x, fixed_t y);
 
 boolean R_DoCulling(line_t *cullheight, line_t *viewcullheight, fixed_t vz, fixed_t bottomh, fixed_t toph);
 
+line_t *R_GetFFloorLine(const seg_t *seg, const ffloor_t *pfloor);
+side_t *R_GetFFloorSide(const seg_t *seg, const ffloor_t *pfloor);
+
 // Render stats
 
 extern precise_t ps_prevframetime;// time when previous frame was rendered
diff --git a/src/r_segs.c b/src/r_segs.c
index 267c1d47d63ff32a56d6e6b0330783397dacfee3..b5d4a6dae1ba1eec2491b609a7f4e991139858fe 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -16,15 +16,10 @@
 #include "r_sky.h"
 
 #include "r_portal.h"
-#include "r_splats.h"
 
 #include "w_wad.h"
 #include "z_zone.h"
-#include "netcode/d_netcmd.h"
-#include "m_misc.h"
-#include "p_local.h" // Camera...
 #include "p_slopes.h"
-#include "console.h" // con_clipviewtop
 #include "taglist.h"
 
 // OPTIMIZE: closed two sided lines as single sided
@@ -79,6 +74,8 @@ static fixed_t *maskedtextureheight = NULL;
 static fixed_t *thicksidecol = NULL;
 static fixed_t *invscale = NULL;
 
+static boolean texcoltables;
+
 //SoM: 3/23/2000: Use boom opening limit removal
 static size_t numopenings;
 static INT16 *openings, *lastopening;
@@ -92,10 +89,6 @@ void R_ClearSegTables(void)
 	curtexturecolumntable = texturecolumntable;
 }
 
-// ==========================================================================
-// R_RenderMaskedSegRange
-// ==========================================================================
-
 transnum_t R_GetLinedefTransTable(fixed_t alpha)
 {
 	return (20*(FRACUNIT - alpha - 1) + FRACUNIT) >> (FRACBITS+1);
@@ -115,8 +108,13 @@ void R_RenderMaskedSegRange(drawseg_t *ds, INT32 x1, INT32 x2)
 	INT32 times, repeats;
 	INT64 overflow_test;
 	INT32 range;
+	UINT8 vertflip;
 	unsigned lengthcol;
 
+	fixed_t wall_scaley;
+	fixed_t scalestep;
+	fixed_t scale1;
+
 	// Calculate light table.
 	// Use different light tables
 	//   for horizontal / vertical / diagonal. Diagonal?
@@ -164,9 +162,17 @@ void R_RenderMaskedSegRange(drawseg_t *ds, INT32 x1, INT32 x2)
 		colfunc = colfuncs[COLDRAWFUNC_FUZZY];
 	}
 
-	fixed_t wall_scaley = sidedef->scaley_mid;
-	fixed_t scalestep = FixedDiv(ds->scalestep, wall_scaley);
-	fixed_t scale1 = FixedDiv(ds->scale1, wall_scaley);
+	vertflip = textures[texnum]->flip & 2;
+
+	wall_scaley = sidedef->scaley_mid;
+	if (wall_scaley < 0)
+	{
+		wall_scaley = -wall_scaley;
+		vertflip = !vertflip;
+	}
+
+	scalestep = FixedDiv(ds->scalestep, wall_scaley);
+	scale1 = FixedDiv(ds->scale1, wall_scaley);
 
 	range = max(ds->x2-ds->x1, 1);
 	rw_scalestep = scalestep;
@@ -175,7 +181,7 @@ void R_RenderMaskedSegRange(drawseg_t *ds, INT32 x1, INT32 x2)
 	// Texture must be cached
 	R_CheckTextureCache(texnum);
 
-	if (textures[texnum]->flip & 2) // vertically flipped?
+	if (vertflip) // vertically flipped?
 		colfunc_2s = R_DrawFlippedMaskedColumn;
 	else
 		colfunc_2s = R_DrawMaskedColumn; // render the usual 2sided single-patch packed texture
@@ -469,6 +475,11 @@ static boolean R_IsFFloorTranslucent(visffloor_t *pfloor)
 	return false;
 }
 
+static fixed_t R_GetSlopeTextureSlide(pslope_t *slope, angle_t lineangle)
+{
+	return FixedMul(slope->zdelta, FINECOSINE((lineangle-slope->xydirection)>>ANGLETOFINESHIFT));
+}
+
 //
 // R_RenderThickSideRange
 // Renders all the thick sides in the given range.
@@ -484,8 +495,6 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	sector_t        tempsec;
 	INT32             templight;
 	INT32             i, p;
-	fixed_t         bottombounds = viewheight << FRACBITS;
-	fixed_t         topbounds = (con_clipviewtop - 1) << FRACBITS;
 	fixed_t         offsetvalue;
 	lightlist_t     *light;
 	r_lightlist_t   *rlight;
@@ -495,12 +504,14 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	INT64         top_frac, top_step, bottom_frac, bottom_step;
 	// skew FOF walls with slopes?
 	fixed_t       ffloortextureslide = 0;
-	INT32         oldx = -1;
+	fixed_t       oldtexturecolumn = -1;
 	fixed_t       left_top, left_bottom; // needed here for slope skewing
 	pslope_t      *skewslope = NULL;
 	boolean do_texture_skew;
 	boolean dont_peg_bottom;
+	fixed_t wall_offsetx;
 	fixed_t wall_scalex, wall_scaley;
+	UINT8 vertflip;
 	unsigned lengthcol;
 
 	void (*colfunc_2s) (column_t *, unsigned);
@@ -513,15 +524,13 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	curline = ds->curline;
 	backsector = pfloor->target;
 	frontsector = curline->frontsector == pfloor->target ? curline->backsector : curline->frontsector;
-	sidedef = &sides[pfloor->master->sidenum[0]];
+	sidedef = R_GetFFloorSide(curline, pfloor);
 
 	colfunc = colfuncs[BASEDRAWFUNC];
 
 	if (pfloor->master->flags & ML_TFERLINE)
 	{
-		size_t linenum = curline->linedef-backsector->lines[0];
-		line_t *newline = pfloor->master->frontsector->lines[0] + linenum;
-		sidedef = &sides[newline->sidenum[0]];
+		line_t *newline = R_GetFFloorLine(curline, pfloor);
 		do_texture_skew = newline->flags & ML_SKEWTD;
 		dont_peg_bottom = newline->flags & ML_DONTPEGBOTTOM;
 	}
@@ -532,6 +541,7 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	}
 
 	texnum = R_GetTextureNum(sidedef->midtexture);
+	vertflip = textures[texnum]->flip & 2;
 
 	if (pfloor->fofflags & FOF_TRANSLUCENT)
 	{
@@ -685,18 +695,25 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 
 	wall_scalex = FixedDiv(FRACUNIT, sidedef->scalex_mid);
 	wall_scaley = sidedef->scaley_mid;
+	if (wall_scaley < 0)
+	{
+		wall_scaley = -wall_scaley;
+		vertflip = !vertflip;
+	}
 
 	thicksidecol = ffloortexturecolumn;
 
+	wall_offsetx = ds->offsetx + sidedef->offsetx_mid;
+
 	if (wall_scalex == FRACUNIT)
 	{
 		for (INT32 x = x1; x <= x2; x++)
-			thicksidecol[x] = ds->thicksidecol[x] + ds->offsetx;
+			thicksidecol[x] = ds->thicksidecol[x];
 	}
 	else
 	{
 		for (INT32 x = x1; x <= x2; x++)
-			thicksidecol[x] = FixedDiv(ds->thicksidecol[x], wall_scalex) + ds->offsetx;
+			thicksidecol[x] = FixedDiv(ds->thicksidecol[x], wall_scalex);
 	}
 
 	mfloorclip = ds->sprbottomclip;
@@ -731,7 +748,7 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	if (skewslope)
 	{
 		angle_t lineangle = R_PointToAngle2(curline->v1->x, curline->v1->y, curline->v2->x, curline->v2->y);
-		ffloortextureslide = FixedMul(skewslope->zdelta, FINECOSINE((lineangle-skewslope->xydirection)>>ANGLETOFINESHIFT));
+		ffloortextureslide = FixedMul(R_GetSlopeTextureSlide(skewslope, lineangle), wall_scaley);
 	}
 
 	dc_texturemid += offsetvalue;
@@ -739,7 +756,7 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 	// Texture must be cached
 	R_CheckTextureCache(texnum);
 
-	if (textures[texnum]->flip & 2) // vertically flipped?
+	if (vertflip) // vertically flipped?
 		colfunc_2s = R_DrawRepeatFlippedMaskedColumn;
 	else
 		colfunc_2s = R_DrawRepeatMaskedColumn; // render the usual 2sided single-patch packed texture
@@ -773,9 +790,9 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 		// skew FOF walls
 		if (ffloortextureslide)
 		{
-			if (oldx != -1)
-				dc_texturemid += FixedMul(ffloortextureslide, thicksidecol[oldx]-thicksidecol[dc_x]);
-			oldx = dc_x;
+			if (oldtexturecolumn != -1)
+				dc_texturemid += FixedMul(ffloortextureslide, oldtexturecolumn-ds->thicksidecol[dc_x]);
+			oldtexturecolumn = ds->thicksidecol[dc_x];
 		}
 
 		// Calculate bounds
@@ -791,7 +808,7 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 		bottom_frac += bottom_step;
 
 		// SoM: If column is out of range, why bother with it??
-		if (windowbottom < topbounds || windowtop > bottombounds)
+		if (windowbottom < 0 || windowtop > (viewheight << FRACBITS))
 		{
 			if (dc_numlights)
 			{
@@ -810,7 +827,7 @@ void R_RenderThickSideRange(drawseg_t *ds, INT32 x1, INT32 x2, ffloor_t *pfloor)
 		dc_iscale = FixedMul(0xffffffffu / (unsigned)spryscale, wall_scaley);
 
 		// Get data for the column
-		col = R_GetColumn(texnum, (thicksidecol[dc_x] >> FRACBITS));
+		col = R_GetColumn(texnum, ((thicksidecol[dc_x] + wall_offsetx) >> FRACBITS));
 
 		// SoM: New code does not rely on R_DrawColumnShadowed_8 which
 		// will (hopefully) put less strain on the stack.
@@ -984,36 +1001,64 @@ static boolean R_FFloorCanClip(visffloor_t *pfloor)
 #define HEIGHTBITS              12
 #define HEIGHTUNIT              (1<<HEIGHTBITS)
 
+static void R_DrawRegularWall(UINT8 *source, INT32 height)
+{
+	dc_source = source;
+	dc_texheight = height;
+	colfunc();
+}
 
-//profile stuff ---------------------------------------------------------
-//#define TIMING
-#ifdef TIMING
-#include "p5prof.h"
-INT64 mycount;
-INT64 mytotal = 0;
-UINT32 nombre = 100000;
-//static   char runtest[10][80];
-#endif
-//profile stuff ---------------------------------------------------------
+static void R_DrawFlippedWall(UINT8 *source, INT32 height)
+{
+	dc_texheight = height;
+	R_DrawFlippedPost(source, (unsigned)height, colfunc);
+}
 
 static void R_RenderSegLoop (void)
 {
 	angle_t angle;
 	fixed_t textureoffset;
-	size_t  pindex;
-	INT32     yl;
-	INT32     yh;
+	size_t pindex;
+	INT32 yl;
+	INT32 yh;
 
-	INT32     mid;
+	INT32 mid;
 	fixed_t texturecolumn = 0;
 	fixed_t toptexturecolumn = 0;
 	fixed_t bottomtexturecolumn = 0;
 	fixed_t oldtexturecolumn = -1;
 	fixed_t oldtexturecolumn_top = -1;
 	fixed_t oldtexturecolumn_bottom = -1;
-	INT32     top;
-	INT32     bottom;
-	INT32     i;
+	INT32 top;
+	INT32 bottom;
+	INT32 i;
+
+	fixed_t topscaley = rw_toptexturescaley;
+	fixed_t midscaley = rw_midtexturescaley;
+	fixed_t bottomscaley = rw_bottomtexturescaley;
+
+	void (*drawtop)(UINT8 *, INT32) = R_DrawRegularWall;
+	void (*drawmiddle)(UINT8 *, INT32) = R_DrawRegularWall;
+	void (*drawbottom)(UINT8 *, INT32) = R_DrawRegularWall;
+
+	if (dc_numlights)
+		colfunc = colfuncs[COLDRAWFUNC_SHADOWED];
+
+	if (toptexture && topscaley < 0)
+	{
+		topscaley = -topscaley;
+		drawtop = R_DrawFlippedWall;
+	}
+	if (midtexture && midscaley < 0)
+	{
+		midscaley = -midscaley;
+		drawmiddle = R_DrawFlippedWall;
+	}
+	if (bottomtexture && bottomscaley < 0)
+	{
+		bottomscaley = -bottomscaley;
+		drawbottom = R_DrawFlippedWall;
+	}
 
 	if (midtexture)
 		R_CheckTextureCache(midtexture);
@@ -1234,8 +1279,6 @@ static void R_RenderSegLoop (void)
 					dc_lightlist[i].rcolormap = dc_lightlist[i].extra_colormap->colormap + (xwalllights[pindex] - colormaps);
 				else
 					dc_lightlist[i].rcolormap = xwalllights[pindex];
-
-				colfunc = colfuncs[COLDRAWFUNC_SHADOWED];
 			}
 		}
 
@@ -1252,24 +1295,9 @@ static void R_RenderSegLoop (void)
 				dc_yl = yl;
 				dc_yh = yh;
 				dc_texturemid = rw_midtexturemid;
-				dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, rw_midtexturescaley);
-				dc_source = R_GetColumn(midtexture, offset >> FRACBITS)->pixels;
 				dc_texheight = textureheight[midtexture]>>FRACBITS;
-
-				//profile stuff ---------------------------------------------------------
-#ifdef TIMING
-				ProfZeroTimer();
-#endif
-				colfunc();
-#ifdef TIMING
-				RDMSR(0x10,&mycount);
-				mytotal += mycount;      //64bit add
-
-				if (nombre--==0)
-					I_Error("R_DrawColumn CPU Spy reports: 0x%d %d\n", *((INT32 *)&mytotal+1),
-						(INT32)mytotal);
-#endif
-				//profile stuff ---------------------------------------------------------
+				dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, midscaley);
+				drawmiddle(R_GetColumn(midtexture, offset >> FRACBITS)->pixels, dc_texheight);
 
 				// dont draw anything more for this column, since
 				// a midtexture blocks the view
@@ -1321,10 +1349,9 @@ static void R_RenderSegLoop (void)
 						dc_yl = yl;
 						dc_yh = mid;
 						dc_texturemid = rw_toptexturemid;
-						dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, rw_toptexturescaley);
-						dc_source = R_GetColumn(toptexture, offset >> FRACBITS)->pixels;
 						dc_texheight = textureheight[toptexture]>>FRACBITS;
-						colfunc();
+						dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, topscaley);
+						drawtop(R_GetColumn(toptexture, offset >> FRACBITS)->pixels, dc_texheight);
 						ceilingclip[rw_x] = (INT16)mid;
 					}
 					else if (!rw_ceilingmarked) // entirely off top of screen
@@ -1334,8 +1361,8 @@ static void R_RenderSegLoop (void)
 					ceilingclip[rw_x] = topclip;
 
 				if (oldtexturecolumn_top != -1)
-					rw_toptexturemid += FixedMul(rw_toptextureslide, oldtexturecolumn_top-toptexturecolumn);
-				oldtexturecolumn_top = toptexturecolumn;
+					rw_toptexturemid += FixedMul(rw_toptextureslide, oldtexturecolumn_top-textureoffset);
+				oldtexturecolumn_top = textureoffset;
 			}
 			else if (markceiling && (!rw_ceilingmarked)) // no top wall
 				ceilingclip[rw_x] = topclip;
@@ -1369,10 +1396,9 @@ static void R_RenderSegLoop (void)
 						dc_yl = mid;
 						dc_yh = yh;
 						dc_texturemid = rw_bottomtexturemid;
-						dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, rw_bottomtexturescaley);
-						dc_source = R_GetColumn(bottomtexture, offset >> FRACBITS)->pixels;
 						dc_texheight = textureheight[bottomtexture]>>FRACBITS;
-						colfunc();
+						dc_iscale = FixedMul(0xffffffffu / (unsigned)rw_scale, bottomscaley);
+						drawbottom(R_GetColumn(bottomtexture, offset >> FRACBITS)->pixels, dc_texheight);
 						floorclip[rw_x] = (INT16)mid;
 					}
 					else if (!rw_floormarked)  // entirely off bottom of screen
@@ -1382,8 +1408,8 @@ static void R_RenderSegLoop (void)
 					floorclip[rw_x] = bottomclip;
 
 				if (oldtexturecolumn_bottom != -1)
-					rw_bottomtexturemid += FixedMul(rw_bottomtextureslide, oldtexturecolumn_bottom-bottomtexturecolumn);
-				oldtexturecolumn_bottom = bottomtexturecolumn;
+					rw_bottomtexturemid += FixedMul(rw_bottomtextureslide, oldtexturecolumn_bottom-textureoffset);
+				oldtexturecolumn_bottom = textureoffset;
 			}
 			else if (markfloor && (!rw_floormarked)) // no bottom wall
 				floorclip[rw_x] = bottomclip;
@@ -1407,11 +1433,14 @@ static void R_RenderSegLoop (void)
 		{
 			if (oldtexturecolumn != -1)
 			{
-				rw_midtexturemid += FixedMul(rw_midtextureslide, oldtexturecolumn-texturecolumn);
-				rw_midtextureback += FixedMul(rw_midtexturebackslide, oldtexturecolumn-texturecolumn);
+				INT32 diff = oldtexturecolumn-textureoffset;
+				if (rw_invmidtexturescalex < 0)
+					diff = -diff;
+				rw_midtexturemid += FixedMul(rw_midtextureslide, diff);
+				rw_midtextureback += FixedMul(rw_midtexturebackslide, diff);
 			}
 
-			oldtexturecolumn = texturecolumn;
+			oldtexturecolumn = textureoffset;
 		}
 
 		if (invscale)
@@ -1505,7 +1534,7 @@ static void R_AllocClippingTables(size_t range)
 static void R_AllocTextureColumnTables(size_t range)
 {
 	size_t pos = curtexturecolumntable - texturecolumntable;
-	size_t need = range * 3;
+	size_t need = range * 4;
 
 	if (pos + need < texturecolumntablesize)
 		return;
@@ -1526,13 +1555,46 @@ static void R_AllocTextureColumnTables(size_t range)
 	for (drawseg_t *ds = drawsegs; ds < ds_p; ds++)
 	{
 		// Check if it's in range of the tables
-		if (ds->maskedtexturecol + ds->x1 >= oldtable && ds->maskedtexturecol + ds->x1 <= oldlast)
-			ds->maskedtexturecol = (ds->maskedtexturecol - oldtable) + texturecolumntable;
-		if (ds->thicksidecol + ds->x1 >= oldtable && ds->thicksidecol + ds->x1 <= oldlast)
-			ds->thicksidecol = (ds->thicksidecol - oldtable) + texturecolumntable;
-		if (ds->invscale + ds->x1 >= oldtable && ds->invscale + ds->x1 <= oldlast)
-			ds->invscale = (ds->invscale - oldtable) + texturecolumntable;
+#define CHECK(which) \
+		if (which + ds->x1 >= oldtable && which + ds->x1 <= oldlast) \
+			which = (which - oldtable) + texturecolumntable
+
+		CHECK(ds->maskedtexturecol);
+		CHECK(ds->maskedtextureheight);
+		CHECK(ds->thicksidecol);
+		CHECK(ds->invscale);
+
+#undef CHECK
+	}
+}
+
+//
+// R_ScaleFromGlobalAngle
+// Returns the texture mapping scale for the current line (horizontal span)
+//  at the given angle.
+// rw_distance must be calculated first.
+//
+// killough 5/2/98: reformatted, cleaned up
+//
+// note: THIS IS USED ONLY FOR WALLS!
+static fixed_t R_ScaleFromGlobalAngle(angle_t visangle)
+{
+	angle_t anglea = ANGLE_90 + (visangle-viewangle);
+	angle_t angleb = ANGLE_90 + (visangle-rw_normalangle);
+	fixed_t den = FixedMul(rw_distance, FINESINE(anglea>>ANGLETOFINESHIFT));
+	// proff 11/06/98: Changed for high-res
+	fixed_t num = FixedMul(projectiony, FINESINE(angleb>>ANGLETOFINESHIFT));
+
+	if (den > num>>16)
+	{
+		num = FixedDiv(num, den);
+		if (num > 64*FRACUNIT)
+			return 64*FRACUNIT;
+		if (num < 256)
+			return 256;
+		return num;
 	}
+	return 64*FRACUNIT;
 }
 
 //
@@ -1706,11 +1768,14 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 
 	midtexture = toptexture = bottomtexture = maskedtexture = 0;
 	ds_p->maskedtexturecol = NULL;
+	ds_p->maskedtextureheight = NULL;
 	ds_p->numthicksides = numthicksides = 0;
 	ds_p->thicksidecol = NULL;
 	ds_p->invscale = NULL;
 	ds_p->tsilheight = 0;
 
+	texcoltables = false;
+
 	numbackffloors = 0;
 
 	for (i = 0; i < MAXFFLOORS; i++)
@@ -1736,16 +1801,19 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 		angle_t lineangle = R_PointToAngle2(curline->v1->x, curline->v1->y, curline->v2->x, curline->v2->y);
 
 		if (frontsector->f_slope)
-			floorfrontslide = FixedMul(frontsector->f_slope->zdelta, FINECOSINE((lineangle-frontsector->f_slope->xydirection)>>ANGLETOFINESHIFT));
+			floorfrontslide = R_GetSlopeTextureSlide(frontsector->f_slope, lineangle);
 
 		if (frontsector->c_slope)
-			ceilingfrontslide = FixedMul(frontsector->c_slope->zdelta, FINECOSINE((lineangle-frontsector->c_slope->xydirection)>>ANGLETOFINESHIFT));
+			ceilingfrontslide = R_GetSlopeTextureSlide(frontsector->c_slope, lineangle);
 
-		if (backsector && backsector->f_slope)
-			floorbackslide = FixedMul(backsector->f_slope->zdelta, FINECOSINE((lineangle-backsector->f_slope->xydirection)>>ANGLETOFINESHIFT));
+		if (backsector)
+		{
+			if (backsector->f_slope)
+				floorbackslide = R_GetSlopeTextureSlide(backsector->f_slope, lineangle);
 
-		if (backsector && backsector->c_slope)
-			ceilingbackslide = FixedMul(backsector->c_slope->zdelta, FINECOSINE((lineangle-backsector->c_slope->xydirection)>>ANGLETOFINESHIFT));
+			if (backsector->c_slope)
+				ceilingbackslide = R_GetSlopeTextureSlide(backsector->c_slope, lineangle);
+		}
 	}
 
 	rw_midtexturescalex = sidedef->scalex_mid;
@@ -1761,26 +1829,27 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 
 		fixed_t rowoffset = sidedef->rowoffset + sidedef->offsety_mid;
 		fixed_t texheight = textureheight[midtexture];
+		fixed_t scaley = abs(rw_midtexturescaley);
 
 		if (rw_midtexturescaley > 0)
 		{
 			if (linedef->flags & ML_NOSKEW)
 			{
 				if (linedef->flags & ML_DONTPEGBOTTOM)
-					rw_midtexturemid = FixedMul(frontsector->floorheight - viewz, rw_midtexturescaley) + texheight;
+					rw_midtexturemid = FixedMul(frontsector->floorheight - viewz, scaley) + texheight;
 				else
-					rw_midtexturemid = FixedMul(frontsector->ceilingheight - viewz, rw_midtexturescaley);
+					rw_midtexturemid = FixedMul(frontsector->ceilingheight - viewz, scaley);
 			}
 			else if (linedef->flags & ML_DONTPEGBOTTOM)
 			{
-				rw_midtexturemid = FixedMul(worldbottom, rw_midtexturescaley) + texheight;
-				rw_midtextureslide = floorfrontslide;
+				rw_midtexturemid = FixedMul(worldbottom, scaley) + texheight;
+				rw_midtextureslide = FixedMul(floorfrontslide, scaley);
 			}
 			else
 			{
 				// top of texture at top
-				rw_midtexturemid = FixedMul(worldtop, rw_midtexturescaley);
-				rw_midtextureslide = ceilingfrontslide;
+				rw_midtexturemid = FixedMul(worldtop, scaley);
+				rw_midtextureslide = FixedMul(ceilingfrontslide, scaley);
 			}
 		}
 		else
@@ -1791,20 +1860,20 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 			if (linedef->flags & ML_NOSKEW)
 			{
 				if (linedef->flags & ML_DONTPEGBOTTOM)
-					rw_midtexturemid = FixedMul(frontsector->floorheight - viewz, rw_midtexturescaley);
+					rw_midtexturemid = FixedMul(frontsector->floorheight - viewz, scaley);
 				else
-					rw_midtexturemid = FixedMul(frontsector->ceilingheight - viewz, rw_midtexturescaley) + texheight;
+					rw_midtexturemid = FixedMul(frontsector->ceilingheight - viewz, scaley) + texheight;
 			}
 			else if (linedef->flags & ML_DONTPEGBOTTOM)
 			{
-				rw_midtexturemid = FixedMul(worldbottom, rw_midtexturescaley);
-				rw_midtextureslide = floorfrontslide;
+				rw_midtexturemid = FixedMul(worldbottom, scaley);
+				rw_midtextureslide = FixedMul(floorfrontslide, scaley);
 			}
 			else
 			{
 				// top of texture at top
-				rw_midtexturemid = FixedMul(worldtop, rw_midtexturescaley) + texheight;
-				rw_midtextureslide = ceilingfrontslide;
+				rw_midtexturemid = FixedMul(worldtop, scaley) + texheight;
+				rw_midtextureslide = FixedMul(ceilingfrontslide, scaley);
 			}
 		}
 
@@ -2013,15 +2082,16 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 			{
 				// top of texture at top
 				rw_toptexturemid = worldtop;
-				rw_toptextureslide = ceilingfrontslide;
+				rw_toptextureslide = FixedMul(ceilingfrontslide, abs(rw_toptexturescaley));
 			}
 			else
 			{
 				rw_toptexturemid = worldhigh + texheight;
-				rw_toptextureslide = ceilingbackslide;
+				rw_toptextureslide = FixedMul(ceilingbackslide, abs(rw_toptexturescaley));
 			}
 
-			rw_toptexturemid = FixedMul(rw_toptexturemid, rw_toptexturescaley);
+			rw_toptexturemid = FixedMul(rw_toptexturemid, abs(rw_toptexturescaley));
+			rw_toptexturemid += toprowoffset;
 		}
 
 		// check BOTTOM TEXTURE
@@ -2052,24 +2122,24 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 				// bottom of texture at bottom
 				// top of texture at top
 				rw_bottomtexturemid = worldbottom;
-				rw_bottomtextureslide = floorfrontslide;
+				rw_bottomtextureslide = FixedMul(floorfrontslide, abs(rw_bottomtexturescaley));
 			}
 			else
 			{
 				// top of texture at top
 				rw_bottomtexturemid = worldlow;
-				rw_bottomtextureslide = floorbackslide;
+				rw_bottomtextureslide = FixedMul(floorbackslide, abs(rw_bottomtexturescaley));
 			}
 
-			rw_bottomtexturemid = FixedMul(rw_bottomtexturemid, rw_bottomtexturescaley);
+			rw_bottomtexturemid = FixedMul(rw_bottomtexturemid, abs(rw_bottomtexturescaley));
+			rw_bottomtexturemid += botrowoffset;
 		}
 
-		rw_toptexturemid += toprowoffset;
-		rw_bottomtexturemid += botrowoffset;
-
 		// allocate space for masked texture tables
 		R_AllocTextureColumnTables(rw_stopx - start);
 
+		texcoltables = true;
+
 		if (frontsector && backsector && !Tag_Compare(&frontsector->tags, &backsector->tags) && (backsector->ffloors || frontsector->ffloors))
 		{
 			ffloor_t *rover;
@@ -2268,7 +2338,8 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 			ds_p->maskedtexturecol = maskedtexturecol = curtexturecolumntable - rw_x;
 			curtexturecolumntable += rw_stopx - rw_x;
 
-			maskedtextureheight = ds_p->maskedtextureheight; // note to red, this == &(ds_p->maskedtextureheight[0])
+			ds_p->maskedtextureheight = maskedtextureheight = curtexturecolumntable - rw_x;
+			curtexturecolumntable += rw_stopx - rw_x;
 
 			maskedtexture = true;
 
@@ -2310,13 +2381,14 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 				}
 			}
 
-			rw_midtexturemid = FixedMul(rw_midtexturemid, rw_midtexturescaley);
-			rw_midtextureback = FixedMul(rw_midtextureback, rw_midtexturescaley);
+			rw_midtexturemid = FixedMul(rw_midtexturemid, abs(rw_midtexturescaley));
+			rw_midtextureback = FixedMul(rw_midtextureback, abs(rw_midtexturescaley));
+
+			rw_midtextureslide = FixedMul(rw_midtextureslide, abs(rw_midtexturescaley));
+			rw_midtexturebackslide = FixedMul(rw_midtexturebackslide, abs(rw_midtexturescaley));
 
 			rw_midtexturemid += sidedef->rowoffset + sidedef->offsety_mid;
 			rw_midtextureback += sidedef->rowoffset + sidedef->offsety_mid;
-
-			maskedtexture = true;
 		}
 	}
 
@@ -2440,7 +2512,7 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 	if (frontsector->numlights)
 	{
 		dc_numlights = frontsector->numlights;
-		if (dc_numlights >= dc_maxlights)
+		if (dc_numlights > dc_maxlights)
 		{
 			dc_maxlights = dc_numlights;
 			dc_lightlist = Z_Realloc(dc_lightlist, sizeof (*dc_lightlist) * dc_maxlights, PU_STATIC, NULL);
diff --git a/src/r_things.c b/src/r_things.c
index d6ef72b9d29980134757df4547ffd03837379957..2d1e27a59dd64d8058710fd75e58922fae0d3944 100644
--- a/src/r_things.c
+++ b/src/r_things.c
@@ -658,12 +658,31 @@ void R_DrawMaskedColumn(column_t *column, unsigned lengthcol)
 static UINT8 *flippedcol = NULL;
 static size_t flippedcolsize = 0;
 
+void R_DrawFlippedPost(UINT8 *source, unsigned length, void (*drawcolfunc)(void))
+{
+	if (!length)
+		return;
+
+	if (!flippedcolsize || length > flippedcolsize)
+	{
+		flippedcolsize = length;
+		flippedcol = Z_Realloc(flippedcol, length, PU_STATIC, NULL);
+	}
+
+	dc_source = flippedcol;
+
+	for (UINT8 *s = (UINT8 *)source, *d = flippedcol+length-1; d >= flippedcol; s++)
+		*d-- = *s;
+
+	drawcolfunc();
+}
+
 void R_DrawFlippedMaskedColumn(column_t *column, unsigned lengthcol)
 {
 	INT32 topscreen;
 	INT32 bottomscreen;
 	fixed_t basetexturemid = dc_texturemid;
-	UINT8 *d,*s;
+	INT32 topdelta;
 
 	for (unsigned i = 0; i < column->num_posts; i++)
 	{
@@ -671,7 +690,7 @@ void R_DrawFlippedMaskedColumn(column_t *column, unsigned lengthcol)
 		if (!post->length)
 			continue;
 
-		INT32 topdelta = lengthcol-post->length-post->topdelta;
+		topdelta = lengthcol-post->length-post->topdelta;
 		topscreen = sprtopscreen + spryscale*topdelta;
 		bottomscreen = sprbotscreen == INT32_MAX ? topscreen + spryscale*post->length
 		                                      : sprbotscreen + spryscale*post->length;
@@ -698,18 +717,9 @@ void R_DrawFlippedMaskedColumn(column_t *column, unsigned lengthcol)
 
 		if (dc_yl <= dc_yh && dc_yh > 0)
 		{
-			if (post->length > flippedcolsize)
-			{
-				flippedcolsize = post->length;
-				flippedcol = Z_Realloc(flippedcol, flippedcolsize, PU_STATIC, NULL);
-			}
-
-			for (s = column->pixels+post->data_offset+post->length, d = flippedcol; d < flippedcol+post->length; --s)
-				*d++ = *s;
-			dc_source = flippedcol;
 			dc_texturemid = basetexturemid - (topdelta<<FRACBITS);
 
-			colfunc();
+			R_DrawFlippedPost(column->pixels + post->data_offset, post->length, colfunc);
 		}
 	}
 
diff --git a/src/r_things.h b/src/r_things.h
index 043b454b049cefa907c16f12c13751236db4b456..f68d75a837ef698bcb98fc4e6dc568f97bf8881a 100644
--- a/src/r_things.h
+++ b/src/r_things.h
@@ -48,6 +48,7 @@ extern fixed_t windowbottom;
 
 void R_DrawMaskedColumn(column_t *column, unsigned lengthcol);
 void R_DrawFlippedMaskedColumn(column_t *column, unsigned lengthcol);
+void R_DrawFlippedPost(UINT8 *source, unsigned length, void (*drawcolfunc)(void));
 
 // ----------------
 // SPRITE RENDERING
diff --git a/src/tables.h b/src/tables.h
index 2736f03e8d57e9d06e90493354302c5403a05f45..65d7f72433177f77d711c5e4b5809ed2f9d6e2b8 100644
--- a/src/tables.h
+++ b/src/tables.h
@@ -81,7 +81,7 @@ extern angle_t tantoangle[SLOPERANGE+1];
 
 // Utility function, called by R_PointToAngle.
 FUNCMATH unsigned SlopeDiv(unsigned num, unsigned den);
-// Only called by R_PointToAngleEx
+// Only called by R_PointToAngle64
 UINT64 SlopeDivEx(unsigned int num, unsigned int den);
 
 // 360 - angle_t(ANGLE_45) = ANGLE_315