diff --git a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
index 2dfaec4..11f03a8 100644
--- a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
+++ b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
@@ -818,6 +818,7 @@ namespace CodeImp.DoomBuilder.BuilderModes
 			}
 
 			Dictionary<int, List<Sector>> sectortags = new Dictionary<int, List<Sector>>();
+			List<Thing> slopethings = new List<Thing>();
 			sectordata = new Dictionary<Sector, SectorData>(General.Map.Map.Sectors.Count);
 			thingdata = new Dictionary<Thing, ThingData>(General.Map.Map.Things.Count);
 
@@ -847,6 +848,15 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
             if (!General.Settings.GZDoomRenderingEffects) return; //mxd
 
+			if (General.Map.SRB2)
+			{
+				// Find all slope vertex things and store them
+				foreach (Thing t in General.Map.Map.Things)
+				{
+					if (t.IsSlopeVertex) slopethings.Add(t);
+				}
+			}
+
             foreach (Sector s in General.Map.Map.Sectors)
 			{
 				// Find all sector whose tag is not 0 and hash them so that we can find them quickly
@@ -1053,31 +1063,28 @@ namespace CodeImp.DoomBuilder.BuilderModes
                             Sidedef side = (l.Args[0] == 0 || l.Args[0] == 1) ? l.Front : l.Back;
                             Sector s = side.Sector;
 
-                            //If NOKNUCKLES is set, use tag, X offset and Y offset to search for slope vertices.
+                            //If Effect 6 is set, use tag, X offset and Y offset to search for slope vertices.
                             if (l.IsFlagSet("8192"))
                             {
                                 bool foundtag = false;
                                 bool foundxoffset = false;
                                 bool foundyoffset = false;
-                                foreach (Thing t in General.Map.Map.Things)
+                                foreach (Thing t in slopethings)
                                 {
-                                    if (t.IsSlopeVertex)
+									if (!foundtag && (int)t.AngleDoom == l.Tag)
                                     {
-                                        if (!foundtag && (int)t.AngleDoom == l.Tag)
-                                        {
-                                            slopevertices.Add(t);
-                                            foundtag = true;
-                                        }
-                                        if (!foundxoffset && (int)t.AngleDoom == side.OffsetX)
-                                        {
-                                            slopevertices.Add(t);
-                                            foundxoffset = true;
-                                        }
-                                        if (!foundyoffset && (int)t.AngleDoom == side.OffsetY)
-                                        {
-                                            slopevertices.Add(t);
-                                            foundyoffset = true;
-                                        }
+                                        slopevertices.Add(t);
+                                        foundtag = true;
+                                    }
+                                    if (!foundxoffset && (int)t.AngleDoom == side.OffsetX)
+                                    {
+                                        slopevertices.Add(t);
+                                        foundxoffset = true;
+                                    }
+                                    if (!foundyoffset && (int)t.AngleDoom == side.OffsetY)
+                                    {
+                                        slopevertices.Add(t);
+                                        foundyoffset = true;
                                     }
                                 }
 
@@ -1085,9 +1092,9 @@ namespace CodeImp.DoomBuilder.BuilderModes
                             //Otherwise, just use tag.
                             else
                             {
-                                foreach (Thing t in General.Map.Map.Things)
+                                foreach (Thing t in slopethings)
                                 {
-                                    if (t.IsSlopeVertex && (int)t.AngleDoom == l.Tag) slopevertices.Add(t);
+                                    if ((int)t.AngleDoom == l.Tag) slopevertices.Add(t);
                                 }
                             }
                             if (slopevertices.Count >= 3)