code: public long getPolyRefBase(MeshTile tile) {
          if (tile == null) {
              return 0;
          }
          int it = tile.index;
          return encodePolyId(tile.salt, it, 0);
      }
docs: Gets the polygon reference for the tile's base polygon.
  
  @param tile
  The tile.
  @return The polygon reference for the base polygon in the specified tile.