Apply clipping optimization for R_ProjectSprite

Author: jserv

src/r_things.c

@@ -457,6 +457,7 @@ void R_ProjectSprite (mobj_t* thing)
 
     fixed_t             gxt;
     fixed_t             gyt;
+    fixed_t             gzt;
 
     fixed_t             tx;
     fixed_t             tz;
@@ -544,15 +545,29 @@ void R_ProjectSprite (mobj_t* thing)
     if (x2 < 0)
         return;
 
+    // clip things which are out of view due to height
+    gzt = thing->z + spritetopoffset[lump];
+    if (thing->z > (int64_t)viewz + FixedDiv(viewheight << FRACBITS, xscale) ||
+        gzt < viewz - FixedDiv((viewheight << FRACBITS) - viewheight, xscale))
+    {
+        return;
+    }
+
+    // quickly reject sprites with bad x ranges
+    if (x1 >= x2)
+    {
+        return;
+    }
+
     // store information in a vissprite
     vis = R_NewVisSprite ();
     vis->mobjflags = thing->flags;
     vis->scale = xscale;
     vis->gx = thing->x;
     vis->gy = thing->y;
     vis->gz = thing->z;
-    vis->gzt = thing->z + spritetopoffset[lump];
-    vis->texturemid = vis->gzt - viewz;
+    vis->gzt = gzt;
+    vis->texturemid = gzt - viewz;
     vis->x1 = x1 < 0 ? 0 : x1;
     vis->x2 = x2 >= viewwidth ? viewwidth-1 : x2;
     const fixed_t iscale = FixedReciprocal(xscale);