- Fixed: 3D floors partitioning the world into different "HeightLevels" could strip a midtexture

of its clipping information before it was drawn. (On the other hand, I have no idea what this
  ds->bkup and refreshing stuff is about, so I might have broken something somewhere else.)

SVN r3602 (trunk)

src/r_segs.cpp

@@ -221,6 +221,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 	int			i;
 	sector_t	tempsec;		// killough 4/13/98
 	fixed_t		texheight, textop, texheightscale;
+	bool		notrelevant = false;
 
 	const sector_t *sec;
 
@@ -360,10 +361,12 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 
 		if ((fake3D & FAKE3D_CLIPBOTTOM) && textop <= sclipBottom - viewz)
 		{
+			notrelevant = true;
 			goto clearfog;
 		}
 		if ((fake3D & FAKE3D_CLIPTOP) && textop - texheight >= sclipTop - viewz)
 		{
+			notrelevant = true;
 			goto clearfog;
 		}
 
@@ -483,6 +486,8 @@ clearfog:
 	{
 		R_RenderFakeWallRange(ds, x1, x2);
 	}
+	if (!notrelevant)
+	{
 		if (fake3D & FAKE3D_REFRESHCLIP)
 		{
 			assert(ds->bkup >= 0);
@@ -492,6 +497,7 @@ clearfog:
 		{
 			clearbufshort(openings + ds->sprtopclip - ds->x1 + x1, x2-x1+1, viewheight);
 		}
+	}
 	return;
 }