draw hole backfaces

src/Arts.cs

@@ -157,6 +157,15 @@ static class Arts
                     1
                 )
             );
+            // [!] have backfaces on a mat run a separate backbox/face shader]? *to try and reduce drawcalls
+            meshes["Hole"].Draw(
+                mat_backbox,
+                Matrix.TRS(
+                    hole.Key.ToVec3,
+                    Quat.LookDir(hole.Value.ToVec3),
+                    1
+                )
+            );
         }