Question describe

Other data is ok, while the second point is in the dividing line of the tile(with buffer), this bug will happan

1. while I use data as blow

{
 "type": "FeatureCollection",
 "features": [
  {
   "type": "Feature",
   "geometry": {
    "type": "Polygon",
    "coordinates": [
     [
      [20.0, 34.365234375],
      [80.0, 4.34326171875],
      [45.0, 4.34326171875],
      [20.0, 4.34326171875],
      [20.0, 34.365234375]
     ]
    ]
   },
   "properties": {
    "title": "路线一",
    "kind": 1
   }
  }
 ]
}

2. set buffer to 0
   

3. the point of this triangle will lost in particular level

Solusion

Why

1. while the three point is in a line, the tolerance of second point is 0
2. while clip the polygon into a child tile, old code, the first and second point have no intersect whit the axis
3. while create a tile, the tolerance is small will be lost for simplify and cause this problem.

For merge request

#161