private static void renderOverlay(
    Rendering rendering, World world, Boardable path[], Colour c
  ) {
    final Batch <Tile> tiles = new Batch <Tile> () ;
    if (path != null) for (Boardable b : path) {
      if (b instanceof Tile) tiles.add((Tile) b) ;
    }
    if (tiles.size() > 0) {
      final TerrainMesh overlay = world.terrain().createOverlay(
        world, tiles.toArray(Tile.class), false, Texture.WHITE_TEX
      ) ;
      overlay.colour = c ;
      rendering.addClient(overlay) ;
    }
  }