d3.geo.tile = function() {
  var size = [960, 500],
      scale = 256,
      translate = [size[0] / 2, size[1] / 2],
      zoomDelta = 0,
      clampX = clamp,
      clampY = clamp;

  function tile() {
    var z = Math.max(Math.log(scale) / Math.LN2 - 8, 0),
        z0 = Math.round(z + zoomDelta),
        k = Math.pow(2, z - z0 + 8),
        origin = [(translate[0] - scale / 2) / k, (translate[1] - scale / 2) / k],
        tiles = [],
        w = 1 << z0,
        x0 = clampX(Math.floor(-origin[0]), w),
        y0 = clampY(Math.floor(-origin[1]), w),
        x1 = clampX(Math.ceil(size[0] / k - origin[0]), w),
        y1 = clampY(Math.ceil(size[1] / k - origin[1]), w);

    for (var y = y0; y < y1; ++y) {
      for (var x = x0; x < x1; ++x) {
        tiles.push([x, y, z0]);
      }
    }

    tiles.translate = origin;
    tiles.scale = k;

    return tiles;
  }

  tile.size = function(_) {
    if (!arguments.length) return size;
    size = _;
    return tile;
  };

  tile.scale = function(_) {
    if (!arguments.length) return scale;
    scale = _;
    return tile;
  };

  tile.translate = function(_) {
    if (!arguments.length) return translate;
    translate = _;
    return tile;
  };

  tile.zoomDelta = function(_) {
    if (!arguments.length) return zoomDelta;
    zoomDelta = +_;
    return tile;
  };

  tile.overflow = function(_) {
    if (!arguments.length) return [clampX === identity, clampY === identity];
    clampX = _[0] ? identity : clamp;
    clampY = _[1] ? identity : clamp;
    return tile;
  };

  return tile;

  function identity(x) { return x; }
  function clamp(x, max) { return Math.max(0, Math.min(max, x)); }
};