public static VectorGeometry encodeFill(double buffer) {
    int min = (int) Math.round(EXTENT * buffer / 256d);
    int width = EXTENT + min + min;
    return new VectorGeometry(new int[]{
      CommandEncoder.commandAndLength(Command.MOVE_TO, 1),
      zigZagEncode(-min), zigZagEncode(-min),
      CommandEncoder.commandAndLength(Command.LINE_TO, 3),
      zigZagEncode(width), 0,
      0, zigZagEncode(width),
      zigZagEncode(-width), 0,
      CommandEncoder.commandAndLength(Command.CLOSE_PATH, 1)
    }, GeometryType.POLYGON, 0);
  }
Returns the encoded geometry for a polygon that fills an entire tile plus {@code buffer} pixels as a shortcut to
avoid needing to create an extra JTS geometry for encoding.
planetiler-core/src/main/java/com/onthegomap/planetiler/VectorTile.java