diff --git a/src/r_bsp.cpp b/src/r_bsp.cpp
index 545d009d9..8ea5c963f 100644
--- a/src/r_bsp.cpp
+++ b/src/r_bsp.cpp
@@ -541,7 +541,7 @@ void R_AddLine (seg_t *line)
 	if (WallC.Init(tx1, ty1, tx2, ty2, 32))
 		return;
 
-	if (WallC.sx1 > WindowRight || WallC.sx2 < WindowLeft)
+	if (WallC.sx1 >= WindowRight || WallC.sx2 <= WindowLeft)
 		return;
 
 	if (line->linedef == NULL)
diff --git a/src/r_main.cpp b/src/r_main.cpp
index b136d9cc6..4cb78311f 100644
--- a/src/r_main.cpp
+++ b/src/r_main.cpp
@@ -667,10 +667,10 @@ void R_EnterMirror (drawseg_t *ds, int depth)
 	ActiveWallMirror = ds->curline;
 
 	R_ClearPlanes (false);
-	R_ClearClipSegs (ds->x1, ds->x2 + 1);
+	R_ClearClipSegs (ds->x1, ds->x2);
 
-	memcpy (ceilingclip + ds->x1, openings + ds->sprtopclip, (ds->x2 - ds->x1 + 1)*sizeof(*ceilingclip));
-	memcpy (floorclip + ds->x1, openings + ds->sprbottomclip, (ds->x2 - ds->x1 + 1)*sizeof(*floorclip));
+	memcpy (ceilingclip + ds->x1, openings + ds->sprtopclip, (ds->x2 - ds->x1)*sizeof(*ceilingclip));
+	memcpy (floorclip + ds->x1, openings + ds->sprbottomclip, (ds->x2 - ds->x1)*sizeof(*floorclip));
 
 	WindowLeft = ds->x1;
 	WindowRight = ds->x2;
@@ -777,7 +777,7 @@ void R_RenderActorView (AActor *actor, bool dontmaplines)
 	}
 
 	WindowLeft = 0;
-	WindowRight = viewwidth - 1;
+	WindowRight = viewwidth;
 	MirrorFlags = 0;
 	ActiveWallMirror = NULL;
 
diff --git a/src/r_plane.cpp b/src/r_plane.cpp
index 84967c164..8238adec2 100644
--- a/src/r_plane.cpp
+++ b/src/r_plane.cpp
@@ -708,8 +708,8 @@ visplane_t *R_FindPlane (const secplane_t &height, FTextureID picnum, int lightl
 	check->colormap = basecolormap;		// [RH] Save colormap
 	check->sky = sky;
 	check->skybox = skybox;
-	check->minx = viewwidth;			// Was SCREENWIDTH -- killough 11/98
-	check->maxx = -1;
+	check->left = viewwidth;			// Was SCREENWIDTH -- killough 11/98
+	check->right = 0;
 	check->extralight = stacked_extralight;
 	check->visibility = stacked_visibility;
 	check->viewx = stacked_viewx;
@@ -740,38 +740,38 @@ visplane_t *R_CheckPlane (visplane_t *pl, int start, int stop)
 	int x;
 
 	assert (start >= 0 && start < viewwidth);
-	assert (stop >= start && stop < viewwidth);
+	assert (stop > start && stop <= viewwidth);
 
-	if (start < pl->minx)
+	if (start < pl->left)
 	{
-		intrl = pl->minx;
+		intrl = pl->left;
 		unionl = start;
 	}
 	else
 	{
-		unionl = pl->minx;
+		unionl = pl->left;
 		intrl = start;
 	}
 		
-	if (stop > pl->maxx)
+	if (stop > pl->right)
 	{
-		intrh = pl->maxx;
+		intrh = pl->right;
 		unionh = stop;
 	}
 	else
 	{
-		unionh = pl->maxx;
+		unionh = pl->right;
 		intrh = stop;
 	}
 
-	for (x = intrl; x <= intrh && pl->top[x] == 0x7fff; x++)
+	for (x = intrl; x < intrh && pl->top[x] == 0x7fff; x++)
 		;
 
-	if (x > intrh)
+	if (x >= intrh)
 	{
 		// use the same visplane
-		pl->minx = unionl;
-		pl->maxx = unionh;
+		pl->left = unionl;
+		pl->right = unionh;
 	}
 	else
 	{
@@ -811,8 +811,8 @@ visplane_t *R_CheckPlane (visplane_t *pl, int start, int stop)
 		new_pl->MirrorFlags = pl->MirrorFlags;
 		new_pl->CurrentSkybox = pl->CurrentSkybox;
 		pl = new_pl;
-		pl->minx = start;
-		pl->maxx = stop;
+		pl->left = start;
+		pl->right = stop;
 		clearbufshort (pl->top, viewwidth, 0x7fff);
 	}
 	return pl;
@@ -922,23 +922,23 @@ static void R_DrawSky (visplane_t *pl)
 {
 	int x;
 
- 	if (pl->minx > pl->maxx)
+ 	if (pl->left >= pl->right)
 		return;
 
 	dc_iscale = skyiscale;
 
-	clearbuf (swall+pl->minx, pl->maxx-pl->minx+1, dc_iscale<<2);
+	clearbuf (swall+pl->left, pl->right-pl->left, dc_iscale<<2);
 
 	if (MirrorFlags & RF_XFLIP)
 	{
-		for (x = pl->minx; x <= pl->maxx; ++x)
+		for (x = pl->left; x < pl->right; ++x)
 		{
 			lwall[x] = (viewwidth - x) << FRACBITS;
 		}
 	}
 	else
 	{
-		for (x = pl->minx; x <= pl->maxx; ++x)
+		for (x = pl->left; x < pl->right; ++x)
 		{
 			lwall[x] = x << FRACBITS;
 		}
@@ -961,7 +961,7 @@ static void R_DrawSky (visplane_t *pl)
 		{
 			lastskycol[x] = 0xffffffff;
 		}
-		wallscan (pl->minx, pl->maxx, (short *)pl->top, (short *)pl->bottom, swall, lwall,
+		wallscan (pl->left, pl->right, (short *)pl->top, (short *)pl->bottom, swall, lwall,
 			frontyScale, backskytex == NULL ? R_GetOneSkyColumn : R_GetTwoSkyColumns);
 	}
 	else
@@ -1001,7 +1001,7 @@ static void R_DrawSkyStriped (visplane_t *pl)
 
 	while (yl < viewheight)
 	{
-		for (x = pl->minx; x <= pl->maxx; ++x)
+		for (x = pl->left; x < pl->right; ++x)
 		{
 			top[x] = MAX (yl, (short)pl->top[x]);
 			bot[x] = MIN (yh, (short)pl->bottom[x]);
@@ -1010,7 +1010,7 @@ static void R_DrawSkyStriped (visplane_t *pl)
 		{
 			lastskycol[x] = 0xffffffff;
 		}
-		wallscan (pl->minx, pl->maxx, top, bot, swall, lwall, rw_pic->yScale,
+		wallscan (pl->left, pl->right, top, bot, swall, lwall, rw_pic->yScale,
 			backskytex == NULL ? R_GetOneSkyColumn : R_GetTwoSkyColumns);
 		yl = yh;
 		yh += drawheight;
@@ -1094,7 +1094,7 @@ void R_DrawSinglePlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 {
 //	pl->angle = pa<<ANGLETOFINESHIFT;
 
-	if (pl->minx > pl->maxx)
+	if (pl->left >= pl->right)
 		return;
 
 	if (r_drawflat)
@@ -1205,7 +1205,7 @@ void R_DrawSkyBoxes ()
 		visplanes[MAXVISPLANES] = pl->next;
 		pl->next = NULL;
 
-		if (pl->maxx < pl->minx || !r_skyboxes || numskyboxes == MAX_SKYBOX_PLANES)
+		if (pl->right < pl->left || !r_skyboxes || numskyboxes == MAX_SKYBOX_PLANES)
 		{
 			R_DrawSinglePlane (pl, OPAQUE, false, false);
 			*freehead = pl;
@@ -1250,11 +1250,11 @@ void R_DrawSkyBoxes ()
 		validcount++;	// Make sure we see all sprites
 
 		R_ClearPlanes (false);
-		R_ClearClipSegs (pl->minx, pl->maxx + 1);
-		WindowLeft = pl->minx;
-		WindowRight = pl->maxx;
+		R_ClearClipSegs (pl->left, pl->right);
+		WindowLeft = pl->left;
+		WindowRight = pl->right;
 
-		for (i = pl->minx; i <= pl->maxx; i++)
+		for (i = pl->left; i < pl->right; i++)
 		{
 			if (pl->top[i] == 0x7fff)
 			{
@@ -1274,16 +1274,16 @@ void R_DrawSkyBoxes ()
 		ds_p->siz2 = INT_MAX;
 		ds_p->sz1 = 0;
 		ds_p->sz2 = 0;
-		ds_p->x1 = pl->minx;
-		ds_p->x2 = pl->maxx;
+		ds_p->x1 = pl->left;
+		ds_p->x2 = pl->right;
 		ds_p->silhouette = SIL_BOTH;
-		ds_p->sprbottomclip = R_NewOpening (pl->maxx - pl->minx + 1);
-		ds_p->sprtopclip = R_NewOpening (pl->maxx - pl->minx + 1);
+		ds_p->sprbottomclip = R_NewOpening (pl->right - pl->left);
+		ds_p->sprtopclip = R_NewOpening (pl->right - pl->left);
 		ds_p->maskedtexturecol = ds_p->swall = -1;
 		ds_p->bFogBoundary = false;
 		ds_p->fake = 0;
-		memcpy (openings + ds_p->sprbottomclip, floorclip + pl->minx, (pl->maxx - pl->minx + 1)*sizeof(short));
-		memcpy (openings + ds_p->sprtopclip, ceilingclip + pl->minx, (pl->maxx - pl->minx + 1)*sizeof(short));
+		memcpy (openings + ds_p->sprbottomclip, floorclip + pl->left, (pl->right - pl->left)*sizeof(short));
+		memcpy (openings + ds_p->sprtopclip, ceilingclip + pl->left, (pl->right - pl->left)*sizeof(short));
 
 		firstvissprite = vissprite_p;
 		firstdrawseg = ds_p++;
@@ -1542,7 +1542,7 @@ void R_DrawNormalPlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 		ystepscale = (DWORD)(-(SDWORD)ystepscale);
 	}
 
-	int x = pl->maxx - halfviewwidth;
+	int x = pl->right - halfviewwidth - 1;
 	planeang = (planeang + (ANG90 >> ANGLETOFINESHIFT)) & FINEMASK;
 	basexfrac = FixedMul (xscale, finecosine[planeang]) + x*xstepscale;
 	baseyfrac = FixedMul (yscale, -finesine[planeang]) + x*ystepscale;
@@ -1742,7 +1742,7 @@ void R_DrawTiltedPlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 
 void R_MapVisPlane (visplane_t *pl, void (*mapfunc)(int y, int x1))
 {
-	int x = pl->maxx;
+	int x = pl->right - 1;
 	int t2 = pl->top[x];
 	int b2 = pl->bottom[x];
 
@@ -1751,7 +1751,7 @@ void R_MapVisPlane (visplane_t *pl, void (*mapfunc)(int y, int x1))
 		clearbufshort (spanend+t2, b2-t2, x);
 	}
 
-	for (--x; x >= pl->minx; --x)
+	for (--x; x >= pl->left; --x)
 	{
 		int t1 = pl->top[x];
 		int b1 = pl->bottom[x];
@@ -1790,7 +1790,7 @@ void R_MapVisPlane (visplane_t *pl, void (*mapfunc)(int y, int x1))
 	// Draw any spans that are still open
 	while (t2 < b2)
 	{
-		mapfunc (--b2, pl->minx);
+		mapfunc (--b2, pl->left);
 	}
 }
 
diff --git a/src/r_plane.h b/src/r_plane.h
index 231fa3ad4..cb1448dcc 100644
--- a/src/r_plane.h
+++ b/src/r_plane.h
@@ -38,7 +38,7 @@ struct visplane_s
 	FTextureID	picnum;
 	int			lightlevel;
 	fixed_t		xoffs, yoffs;		// killough 2/28/98: Support scrolling flats
-	int			minx, maxx;
+	int			left, right;
 	FDynamicColormap *colormap;			// [RH] Support multiple colormaps
 	fixed_t		xscale, yscale;		// [RH] Support flat scaling
 	angle_t		angle;				// [RH] Support flat rotation
diff --git a/src/r_segs.cpp b/src/r_segs.cpp
index ebf525569..d55b31bbe 100644
--- a/src/r_segs.cpp
+++ b/src/r_segs.cpp
@@ -206,13 +206,13 @@ void ClipMidtex(int x1, int x2)
 	short most[MAXWIDTH];
 
 	WallMost(most, curline->frontsector->ceilingplane, &WallC);
-	for (int i = x1; i <= x2; ++i)
+	for (int i = x1; i < x2; ++i)
 	{
 		if (wallupper[i] < most[i])
 			wallupper[i] = most[i];
 	}
 	WallMost(most, curline->frontsector->floorplane, &WallC);
-	for (int i = x1; i <= x2; ++i)
+	for (int i = x1; i < x2; ++i)
 	{
 		if (walllower[i] > most[i])
 			walllower[i] = most[i];
@@ -398,12 +398,12 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 			OWallMost(walllower, textop - texheight, &WallC);
 		}
 
-		for (i = x1; i <= x2; i++)
+		for (i = x1; i < x2; i++)
 		{
 			if (wallupper[i] < mceilingclip[i])
 				wallupper[i] = mceilingclip[i];
 		}
-		for (i = x1; i <= x2; i++)
+		for (i = x1; i < x2; i++)
 		{
 			if (walllower[i] > mfloorclip[i])
 				walllower[i] = mfloorclip[i];
@@ -426,7 +426,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 		// draw the columns one at a time
 		if (drawmode == DoDraw0)
 		{
-			for (dc_x = x1; dc_x <= x2; ++dc_x)
+			for (dc_x = x1; dc_x < x2; ++dc_x)
 			{
 				BlastMaskedColumn (R_DrawMaskedColumn, tex);
 			}
@@ -434,9 +434,9 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 		else
 		{
 			// [RH] Draw up to four columns at once
-			int stop = (x2+1) & ~3;
+			int stop = x2 & ~3;
 
-			if (x1 > x2)
+			if (x1 >= x2)
 				goto clearfog;
 
 			dc_x = x1;
@@ -458,7 +458,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 				dc_x++;
 			}
 
-			while (dc_x <= x2)
+			while (dc_x < x2)
 			{
 				BlastMaskedColumn (R_DrawMaskedColumn, tex);
 				dc_x++;
@@ -486,7 +486,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 		if (fake3D & FAKE3D_CLIPTOP)
 		{
 			OWallMost(wallupper, sclipTop - viewz, &WallC);
-			for (i = x1; i <= x2; i++)
+			for (i = x1; i < x2; i++)
 			{
 				if (wallupper[i] < mceilingclip[i])
 					wallupper[i] = mceilingclip[i];
@@ -496,7 +496,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 		if (fake3D & FAKE3D_CLIPBOTTOM)
 		{
 			OWallMost(walllower, sclipBottom - viewz, &WallC);
-			for (i = x1; i <= x2; i++)
+			for (i = x1; i < x2; i++)
 			{
 				if (walllower[i] > mfloorclip[i])
 					walllower[i] = mfloorclip[i];
@@ -520,11 +520,11 @@ clearfog:
 		if (fake3D & FAKE3D_REFRESHCLIP)
 		{
 			assert(ds->bkup >= 0);
-			memcpy(openings + ds->sprtopclip, openings + ds->bkup, (ds->x2-ds->x1+1) * 2);
+			memcpy(openings + ds->sprtopclip, openings + ds->bkup, (ds->x2 - ds->x1) * 2);
 		}
 		else
 		{
-			clearbufshort(openings + ds->sprtopclip - ds->x1 + x1, x2-x1+1, viewheight);
+			clearbufshort(openings + ds->sprtopclip - ds->x1 + x1, x2 - x1, viewheight);
 		}
 	}
 	return;
@@ -539,7 +539,7 @@ void R_RenderFakeWall(drawseg_t *ds, int x1, int x2, F3DFloor *rover)
 	fixed_t Alpha = Scale(rover->alpha, OPAQUE, 255);
 	ESPSResult drawmode;
 	drawmode = R_SetPatchStyle (LegacyRenderStyles[rover->flags & FF_ADDITIVETRANS ? STYLE_Add : STYLE_Translucent],
-		Alpha,	0, 0);
+		Alpha, 0, 0);
 
 	if(drawmode == DontDraw) {
 		R_FinishSetPatchStyle();
@@ -617,12 +617,12 @@ void R_RenderFakeWall(drawseg_t *ds, int x1, int x2, F3DFloor *rover)
 	OWallMost(wallupper, sclipTop - viewz, &WallC);
 	OWallMost(walllower, sclipBottom - viewz, &WallC);
 
-	for (i = x1; i <= x2; i++)
+	for (i = x1; i < x2; i++)
 	{
 		if (wallupper[i] < mceilingclip[i])
 			wallupper[i] = mceilingclip[i];
 	}
-	for (i = x1; i <= x2; i++)
+	for (i = x1; i < x2; i++)
 	{
 		if (walllower[i] > mfloorclip[i])
 			walllower[i] = mfloorclip[i];
@@ -1093,7 +1093,7 @@ void wallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixed_t
 		palookupoffse[3] = dc_colormap;
 	}
 
-	for(; (x <= x2) && (x & 3); ++x)
+	for(; (x < x2) && (x & 3); ++x)
 	{
 		light += rw_lightstep;
 		y1ve[0] = uwal[x];//max(uwal[x],umost[x]);
@@ -1116,7 +1116,7 @@ void wallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixed_t
 		dovline1();
 	}
 
-	for(; x <= x2-3; x += 4)
+	for(; x < x2-3; x += 4)
 	{
 		bad = 0;
 		for (z = 3; z>= 0; --z)
@@ -1186,7 +1186,7 @@ void wallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixed_t
 			}
 		}
 	}
-	for(;x<=x2;x++)
+	for(;x<x2;x++)
 	{
 		light += rw_lightstep;
 		y1ve[0] = uwal[x];//max(uwal[x],umost[x]);
@@ -1227,7 +1227,7 @@ void wallscan_striped (int x1, int x2, short *uwal, short *dwal, fixed_t *swal,
 	down = most1;
 
 	assert(WallC.sx1 <= x1);
-	assert(WallC.sx2 > x2);
+	assert(WallC.sx2 >= x2);
 
 	// kg3D - fake floors instead of zdoom light list
 	for (unsigned int i = 0; i < frontsector->e->XFloor.lightlist.Size(); i++)
@@ -1235,7 +1235,7 @@ void wallscan_striped (int x1, int x2, short *uwal, short *dwal, fixed_t *swal,
 		int j = WallMost (most3, frontsector->e->XFloor.lightlist[i].plane, &WallC);
 		if (j != 3)
 		{
-			for (int j = x1; j <= x2; ++j)
+			for (int j = x1; j < x2; ++j)
 			{
 				down[j] = clamp (most3[j], up[j], dwal[j]);
 			}
@@ -1317,7 +1317,7 @@ void wallscan_np2(int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixed
 				int j = OWallMost(most3, partition - viewz, &WallC);
 				if (j != 3)
 				{
-					for (int j = x1; j <= x2; ++j)
+					for (int j = x1; j < x2; ++j)
 					{
 						down[j] = clamp(most3[j], up[j], dwal[j]);
 					}
@@ -1341,7 +1341,7 @@ void wallscan_np2(int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixed
 				int j = OWallMost(most3, partition - viewz, &WallC);
 				if (j != 12)
 				{
-					for (int j = x1; j <= x2; ++j)
+					for (int j = x1; j < x2; ++j)
 					{
 						up[j] = clamp(most3[j], uwal[j], down[j]);
 					}
@@ -1460,7 +1460,7 @@ void maskwallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixe
 		domvline1();
 	}
 
-	for(; x <= x2-3; x += 4, p+= 4)
+	for(; x < x2-3; x += 4, p+= 4)
 	{
 		bad = 0;
 		for (z = 3, dax = x+3; z >= 0; --z, --dax)
@@ -1528,7 +1528,7 @@ void maskwallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal, fixe
 			}
 		}
 	}
-	for(; x <= x2; ++x, ++p)
+	for(; x < x2; ++x, ++p)
 	{
 		light += rw_lightstep;
 		y1ve[0] = uwal[x];
@@ -1612,7 +1612,7 @@ void transmaskwallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal,
 		palookupoffse[3] = dc_colormap;
 	}
 
-	for(; (x <= x2) && ((size_t)p & 3); ++x, ++p)
+	for(; (x < x2) && ((size_t)p & 3); ++x, ++p)
 	{
 		light += rw_lightstep;
 		y1ve[0] = uwal[x];//max(uwal[x],umost[x]);
@@ -1633,7 +1633,7 @@ void transmaskwallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal,
 		tmvline1();
 	}
 
-	for(; x <= x2-3; x += 4, p+= 4)
+	for(; x < x2-3; x += 4, p+= 4)
 	{
 		bad = 0;
 		for (z = 3, dax = x+3; z >= 0; --z, --dax)
@@ -1704,7 +1704,7 @@ void transmaskwallscan (int x1, int x2, short *uwal, short *dwal, fixed_t *swal,
 			}
 		}
 	}
-	for(; x <= x2; ++x, ++p)
+	for(; x < x2; ++x, ++p)
 	{
 		light += rw_lightstep;
 		y1ve[0] = uwal[x];
@@ -1855,11 +1855,11 @@ void R_RenderSegLoop ()
 			}
 			if (rw_pic->GetHeight() != 1 << rw_pic->HeightBits)
 			{
-				wallscan_np2(x1, x2-1, walltop, wallbottom, swall, lwall, yscale, MAX(rw_frontcz1, rw_frontcz2), MIN(rw_frontfz1, rw_frontfz2), false);
+				wallscan_np2(x1, x2, walltop, wallbottom, swall, lwall, yscale, MAX(rw_frontcz1, rw_frontcz2), MIN(rw_frontfz1, rw_frontfz2), false);
 			}
 			else
 			{
-				call_wallscan(x1, x2-1, walltop, wallbottom, swall, lwall, yscale, false);
+				call_wallscan(x1, x2, walltop, wallbottom, swall, lwall, yscale, false);
 			}
 		}
 		clearbufshort (ceilingclip+x1, x2-x1, viewheight);
@@ -1898,11 +1898,11 @@ void R_RenderSegLoop ()
 				}
 				if (rw_pic->GetHeight() != 1 << rw_pic->HeightBits)
 				{
-					wallscan_np2(x1, x2-1, walltop, wallupper, swall, lwall, yscale, MAX(rw_frontcz1, rw_frontcz2), MIN(rw_backcz1, rw_backcz2), false);
+					wallscan_np2(x1, x2, walltop, wallupper, swall, lwall, yscale, MAX(rw_frontcz1, rw_frontcz2), MIN(rw_backcz1, rw_backcz2), false);
 				}
 				else
 				{
-					call_wallscan(x1, x2-1, walltop, wallupper, swall, lwall, yscale, false);
+					call_wallscan(x1, x2, walltop, wallupper, swall, lwall, yscale, false);
 				}
 			}
 			memcpy (ceilingclip+x1, wallupper+x1, (x2-x1)*sizeof(short));
@@ -1944,11 +1944,11 @@ void R_RenderSegLoop ()
 				}
 				if (rw_pic->GetHeight() != 1 << rw_pic->HeightBits)
 				{
-					wallscan_np2(x1, x2-1, walllower, wallbottom, swall, lwall, yscale, MAX(rw_backfz1, rw_backfz2), MIN(rw_frontfz1, rw_frontfz2), false);
+					wallscan_np2(x1, x2, walllower, wallbottom, swall, lwall, yscale, MAX(rw_backfz1, rw_backfz2), MIN(rw_frontfz1, rw_frontfz2), false);
 				}
 				else
 				{
-					call_wallscan(x1, x2-1, walllower, wallbottom, swall, lwall, yscale, false);
+					call_wallscan(x1, x2, walllower, wallbottom, swall, lwall, yscale, false);
 				}
 			}
 			memcpy (floorclip+x1, walllower+x1, (x2-x1)*sizeof(short));
@@ -2368,7 +2368,7 @@ void R_StoreWallRange (int start, int stop)
 	ds_p->siz1 = (DWORD)DivScale32 (1, WallC.sz1) >> 1;
 	ds_p->siz2 = (DWORD)DivScale32 (1, WallC.sz2) >> 1;
 	ds_p->x1 = rw_x = start;
-	ds_p->x2 = stop-1;
+	ds_p->x2 = stop;
 	ds_p->curline = curline;
 	rw_stopx = stop;
 	ds_p->bFogBoundary = false;
@@ -2547,7 +2547,7 @@ void R_StoreWallRange (int start, int stop)
 	{
 		if (ceilingplane)
 		{	// killough 4/11/98: add NULL ptr checks
-			ceilingplane = R_CheckPlane (ceilingplane, start, stop-1);
+			ceilingplane = R_CheckPlane (ceilingplane, start, stop);
 		}
 		else
 		{
@@ -2559,7 +2559,7 @@ void R_StoreWallRange (int start, int stop)
 	{
 		if (floorplane)
 		{	// killough 4/11/98: add NULL ptr checks
-			floorplane = R_CheckPlane (floorplane, start, stop-1);
+			floorplane = R_CheckPlane (floorplane, start, stop);
 		}
 		else
 		{
@@ -2707,8 +2707,8 @@ int OWallMost (short *mostbuf, fixed_t z, const FWallCoords *wallc)
 #endif
 	if (mostbuf[ix1] < 0) mostbuf[ix1] = 0;
 	else if (mostbuf[ix1] > viewheight) mostbuf[ix1] = (short)viewheight;
-	if (mostbuf[ix2] < 0) mostbuf[ix2] = 0;
-	else if (mostbuf[ix2] > viewheight) mostbuf[ix2] = (short)viewheight;
+	if (mostbuf[ix2-1] < 0) mostbuf[ix2-1] = 0;
+	else if (mostbuf[ix2-1] > viewheight) mostbuf[ix2-1] = (short)viewheight;
 
 	return bad;
 }
@@ -2865,8 +2865,8 @@ int WallMost (short *mostbuf, const secplane_t &plane, const FWallCoords *wallc)
 
 	if (mostbuf[ix1] < 0) mostbuf[ix1] = 0;
 	else if (mostbuf[ix1] > viewheight) mostbuf[ix1] = (short)viewheight;
-	if (mostbuf[ix2] < 0) mostbuf[ix2] = 0;
-	else if (mostbuf[ix2] > viewheight) mostbuf[ix2] = (short)viewheight;
+	if (mostbuf[ix2-1] < 0) mostbuf[ix2-1] = 0;
+	else if (mostbuf[ix2-1] > viewheight) mostbuf[ix2-1] = (short)viewheight;
 
 	return bad;
 }
@@ -3063,7 +3063,7 @@ static void R_RenderDecal (side_t *wall, DBaseDecal *decal, drawseg_t *clipper,
 	x1 = WallC.sx1;
 	x2 = WallC.sx2;
 
-	if (x1 > clipper->x2 || x2 <= clipper->x1)
+	if (x1 >= clipper->x2 || x2 <= clipper->x1)
 		goto done;
 
 	WallT.InitFromWallCoords(&WallC);
@@ -3126,14 +3126,8 @@ static void R_RenderDecal (side_t *wall, DBaseDecal *decal, drawseg_t *clipper,
 	dc_texturemid = topoff + FixedDiv (zpos - viewz, yscale);
 
 	// Clip sprite to drawseg
-	if (x1 < clipper->x1)
-	{
-		x1 = clipper->x1;
-	}
-	if (x2 > clipper->x2)
-	{
-		x2 = clipper->x2 + 1;
-	}
+	x1 = MAX<int>(clipper->x1, x1);
+	x2 = MIN<int>(clipper->x2, x2);
 	if (x1 >= x2)
 	{
 		goto done;
diff --git a/src/r_things.cpp b/src/r_things.cpp
index 8ad5f76a9..57a82ebb0 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -352,7 +352,7 @@ void R_DrawVisSprite (vissprite_t *vis)
 		else	 // DoDraw1
 		{
 			// Up to four columns at a time
-			stop4 = (vis->x2 + 1) & ~3;
+			stop4 = vis->x2 & ~3;
 		}
 
 		tex = vis->pic;
@@ -366,7 +366,7 @@ void R_DrawVisSprite (vissprite_t *vis)
 		sprtopscreen = centeryfrac - FixedMul (dc_texturemid, spryscale);
 
 		dc_x = vis->x1;
-		x2 = vis->x2 + 1;
+		x2 = vis->x2;
 
 		if (dc_x < x2)
 		{
@@ -412,7 +412,7 @@ void R_DrawWallSprite(vissprite_t *spr)
 	fixed_t yscale;
 
 	x1 = MAX<int>(spr->x1, spr->wallc.sx1);
-	x2 = MIN<int>(spr->x2 + 1, spr->wallc.sx2 + 1);
+	x2 = MIN<int>(spr->x2, spr->wallc.sx2);
 	if (x1 >= x2)
 		return;
 	WallT.InitFromWallCoords(&spr->wallc);
@@ -868,7 +868,7 @@ void R_ProjectSprite (AActor *thing, int fakeside, F3DFloor *fakefloor, F3DFloor
 		x1 = centerx + MulScale32 (tx, xscale);
 
 		// off the right side?
-		if (x1 > WindowRight)
+		if (x1 >= WindowRight)
 			return;
 
 		tx += tex->GetWidth() * thingxscalemul;
@@ -880,7 +880,6 @@ void R_ProjectSprite (AActor *thing, int fakeside, F3DFloor *fakefloor, F3DFloor
 
 		xscale = FixedDiv(FixedMul(spritescaleX, xscale), tex->xScale);
 		iscale = (tex->GetWidth() << FRACBITS) / (x2 - x1);
-		x2--;
 
 		fixed_t yscale = SafeDivScale16(spritescaleY, tex->yScale);
 
@@ -1062,7 +1061,7 @@ static void R_ProjectWallSprite(AActor *thing, fixed_t fx, fixed_t fy, fixed_t f
 	if (wallc.Init(lx1, ly1, lx2, ly2, TOO_CLOSE_Z))
 		return;
 	
-	if (wallc.sx1 > WindowRight || wallc.sx2 <= WindowLeft)
+	if (wallc.sx1 >= WindowRight || wallc.sx2 <= WindowLeft)
 		return;
 
 	// Sprite sorting should probably treat these as walls, not sprites,
@@ -1076,7 +1075,7 @@ static void R_ProjectWallSprite(AActor *thing, fixed_t fx, fixed_t fy, fixed_t f
 
 	vis = R_NewVisSprite();
 	vis->x1 = wallc.sx1 < WindowLeft ? WindowLeft : wallc.sx1;
-	vis->x2 = wallc.sx2 >= WindowRight ? WindowRight : wallc.sx2-1;
+	vis->x2 = wallc.sx2 >= WindowRight ? WindowRight : wallc.sx2;
 	vis->yscale = yscale;
 	vis->idepth = (unsigned)DivScale32(1, tz) >> 1;
 	vis->depth = tz;
@@ -1213,10 +1212,10 @@ void R_DrawPSprite (pspdef_t* psp, int pspnum, AActor *owner, fixed_t sx, fixed_
 		return; 
 
 	tx += tex->GetScaledWidth() << FRACBITS;
-	x2 = ((centerxfrac + FixedMul (tx, pspritexscale)) >>FRACBITS) - 1;
+	x2 = ((centerxfrac + FixedMul (tx, pspritexscale)) >>FRACBITS);
 
 	// off the left side
-	if (x2 < 0)
+	if (x2 <= 0)
 		return;
 	
 	// store information in a vissprite
@@ -1255,7 +1254,7 @@ void R_DrawPSprite (pspdef_t* psp, int pspnum, AActor *owner, fixed_t sx, fixed_
 		vis->texturemid -= BaseRatioSizes[WidescreenRatio][2];
 	}
 	vis->x1 = x1 < 0 ? 0 : x1;
-	vis->x2 = x2 >= viewwidth ? viewwidth-1 : x2;
+	vis->x2 = x2 >= viewwidth ? viewwidth : x2;
 	vis->xscale = DivScale16(pspritexscale, tex->xScale);
 	vis->yscale = DivScale16(pspriteyscale, tex->yScale);
 	vis->Translation = 0;		// [RH] Use default colors
@@ -1807,7 +1806,7 @@ void R_DrawSprite (vissprite_t *spr)
 	x2 = spr->x2;
 
 	// [RH] Quickly reject sprites with bad x ranges.
-	if (x1 > x2)
+	if (x1 >= x2)
 		return;
 
 	// [RH] Sprites split behind a one-sided line can also be discarded.
@@ -2050,7 +2049,7 @@ void R_DrawSprite (vissprite_t *spr)
 		return;
 	}
 
-	i = x2 - x1 + 1;
+	i = x2 - x1;
 	clip1 = clipbot + x1;
 	clip2 = cliptop + x1;
 	do
@@ -2073,7 +2072,7 @@ void R_DrawSprite (vissprite_t *spr)
 		// kg3D - no clipping on fake segs
 		if(ds->fake) continue;
 		// determine if the drawseg obscures the sprite
-		if (ds->x1 > x2 || ds->x2 < x1 ||
+		if (ds->x1 >= x2 || ds->x2 <= x1 ||
 			(!(ds->silhouette & SIL_BOTH) && ds->maskedtexturecol == -1 &&
 			 !ds->bFogBoundary) )
 		{
@@ -2116,7 +2115,7 @@ void R_DrawSprite (vissprite_t *spr)
 		{
 			clip1 = clipbot + r1;
 			clip2 = openings + ds->sprbottomclip + r1 - ds->x1;
-			i = r2 - r1 + 1;
+			i = r2 - r1;
 			do
 			{
 				if (*clip1 > *clip2)
@@ -2130,7 +2129,7 @@ void R_DrawSprite (vissprite_t *spr)
 		{
 			clip1 = cliptop + r1;
 			clip2 = openings + ds->sprtopclip + r1 - ds->x1;
-			i = r2 - r1 + 1;
+			i = r2 - r1;
 			do
 			{
 				if (*clip1 < *clip2)
@@ -2182,7 +2181,7 @@ void R_DrawSprite (vissprite_t *spr)
 		}
 		if (x2 < viewwidth - 1)
 		{
-			clearbufshort(cliptop + x2 + 1, viewwidth - x2 - 1, viewheight);
+			clearbufshort(cliptop + x2, viewwidth - x2, viewheight);
 		}
 		int minvoxely = spr->gzt <= hzt ? 0 : (spr->gzt - hzt) / spr->yscale;
 		int maxvoxely = spr->gzb > hzb ? INT_MAX : (spr->gzt - hzb) / spr->yscale;
@@ -2459,13 +2458,13 @@ static void R_DrawMaskedSegsBehindParticle (const vissprite_t *vis)
 		drawseg_t *ds = &drawsegs[InterestingDrawsegs[p]];
 		// kg3D - no fake segs
 		if(ds->fake) continue;
-		if (ds->x1 >= x2 || ds->x2 < x1)
+		if (ds->x1 >= x2 || ds->x2 <= x1)
 		{
 			continue;
 		}
 		if (Scale (ds->siz2 - ds->siz1, (x2 + x1)/2 - ds->sx1, ds->sx2 - ds->sx1) + ds->siz1 < vis->idepth)
 		{
-			R_RenderMaskedSegRange (ds, MAX<int> (ds->x1, x1), MIN<int> (ds->x2, x2-1));
+			R_RenderMaskedSegRange (ds, MAX<int>(ds->x1, x1), MIN<int>(ds->x2, x2));
 		}
 	}
 }
@@ -2480,7 +2479,7 @@ void R_DrawParticle (vissprite_t *vis)
 	int yl = vis->gzb;
 	int ycount = vis->gzt - yl + 1;
 	int x1 = vis->x1;
-	int countbase = vis->x2 - x1 + 1;
+	int countbase = vis->x2 - x1;
 
 	R_DrawMaskedSegsBehindParticle (vis);