Some cherrypicks from SRB2 Classic's 'Faster software drawing'

-Textures with 0 height are not checked for wraps, this helps speed up multipatch columns.
-A useless call to R_FakeFlat has been removed.
-Slopes now use floats rather than doubles to calculate UV coordinates.

src/r_draw_column.cpp

@@ -225,7 +225,21 @@ static void R_DrawColumnTemplate(drawcolumndata_t *dc)
 		npow2min = -1;
 		npow2max = dc->sourcelength;
 
-		if (dc->sourcelength & heightmask)   // not a power of 2 -- killough
+		if (heightmask == -1)
+		{
+			if (frac < 0)
+				// adjust in case we underread
+				frac += FRACUNIT;
+
+			// texture has no height, so just go
+			while (--count > 0)
+			{
+				INT32 n = frac >> FRACBITS;
+				dest += vid.width;
+				*dest = R_DrawColumnPixel<Type>(dc, dest, n);
+			}
+		}
+		else if (dc->texheight & heightmask)   // not a power of 2 -- killough
 		{
 			heightmask = dc->texheight << FRACBITS;
 

src/r_draw_span.cpp

@@ -255,7 +255,7 @@ static void R_DrawTiltedSpanTemplate(drawspandata_t* ds)
 {
 	// x1, x2 = ds_x1, ds_x2
 	int width = ds->x2 - ds->x1;
-	double iz, uz, vz;
+	float iz, uz, vz;
 	UINT32 u, v;
 	int i;
 
@@ -263,9 +263,9 @@ static void R_DrawTiltedSpanTemplate(drawspandata_t* ds)
 	UINT8 *dest;
 	UINT8 *dsrc;
 
-	double startz, startu, startv;
+	float startz, startu, startv;
-	double izstep, uzstep, vzstep;
+	float izstep, uzstep, vzstep;
-	double endz, endu, endv;
+	float endz, endu, endv;
 	UINT32 stepu, stepv;
 	UINT32 bit;
 	INT32 tiltlighting[MAXVIDWIDTH];
@@ -390,7 +390,7 @@ static void R_DrawTiltedSpanTemplate(drawspandata_t* ds)
 		}
 		else
 		{
-			double left = width;
+			float left = width;
 			iz += ds->szp.x * left;
 			uz += ds->sup.x * left;
 			vz += ds->svp.x * left;
@@ -514,7 +514,7 @@ static void R_DrawTiltedNPO2SpanTemplate(drawspandata_t* ds)
 {
 	// x1, x2 = ds_x1, ds_x2
 	int width = ds->x2 - ds->x1;
-	double iz, uz, vz;
+	float iz, uz, vz;
 	UINT32 u, v;
 	int i;
 
@@ -522,9 +522,9 @@ static void R_DrawTiltedNPO2SpanTemplate(drawspandata_t* ds)
 	UINT8 *dest;
 	UINT8 *dsrc;
 
-	double startz, startu, startv;
+	float startz, startu, startv;
-	double izstep, uzstep, vzstep;
+	float izstep, uzstep, vzstep;
-	double endz, endu, endv;
+	float endz, endu, endv;
 	UINT32 stepu, stepv;
 	INT32 tiltlighting[MAXVIDWIDTH];
 
@@ -689,7 +689,7 @@ static void R_DrawTiltedNPO2SpanTemplate(drawspandata_t* ds)
 		}
 		else
 		{
-			double left = width;
+			float left = width;
 			iz += ds->szp.x * left;
 			uz += ds->sup.x * left;
 			vz += ds->svp.x * left;