lib/Map/MapboxVectorTileImageryProvider.js
function overzoomGeometry(rings, nativeTile, newExtent, newTile) {
  var diffZ = newTile.level - nativeTile.level;
  if (diffZ === 0) {
    return rings;
  } else {
    var newRings = [];
    // (offsetX, offsetY) is the (0,0) of the new tile
    var offsetX = newExtent * (newTile.x - (nativeTile.x << diffZ));
    var offsetY = newExtent * (newTile.y - (nativeTile.y << diffZ));
    for (var i = 0; i < rings.length; i++) {
      var ring = [];
      for (var i2 = 0; i2 < rings[i].length; i2++) {
        ring.push(rings[i][i2].sub(new Point(offsetX, offsetY)));
      }
      newRings.push(ring);
    }
    return newRings;
  }
}
function overzoomGeometry(rings, nativeTile, newExtent, newTile) {
  var diffZ = newTile.level - nativeTile.level;
  if (diffZ === 0) {
    return rings;
  } else {
    var newRings = [];
    // (offsetX, offsetY) is the (0,0) of the new tile
    var offsetX = newExtent * (newTile.x - (nativeTile.x << diffZ));
    var offsetY = newExtent * (newTile.y - (nativeTile.y << diffZ));
    for (var i = 0; i < rings.length; i++) {
      var ring = [];
      for (var i2 = 0; i2 < rings[i].length; i2++) {
        ring.push(rings[i][i2].sub(new Point(offsetX, offsetY)));
      }
      newRings.push(ring);
    }
    return newRings;
  }
}
function overzoomGeometry ( rings , nativeTile , newExtent , newTile ) { var diffZ = newTile . level - nativeTile . level ; if ( diffZ === 0 ) { return rings ; } else { var newRings = [ ] ; // (offsetX, offsetY) is the (0,0) of the new tile var offsetX = newExtent * ( newTile . x - ( nativeTile . x << diffZ ) ) ; var offsetY = newExtent * ( newTile . y - ( nativeTile . y << diffZ ) ) ; for ( var i = 0 ; i < rings . length ; i ++ ) { var ring = [ ] ; for ( var i2 = 0 ; i2 < rings [ i ] . length ; i2 ++ ) { ring . push ( rings [ i ] [ i2 ] . sub ( new Point ( offsetX , offsetY ) ) ) ; } newRings . push ( ring ) ; } return newRings ; } }
Use x,y,level vector tile to produce imagery for newX,newY,newLevel
Use x y level vector tile to produce imagery for newX newY newLevel