code: func VisvalingamThreshold(path *geo.Path, threshold float64) *geo.Path {
  	return Visvalingam(path, threshold, 0)
  }
docs: // VisvalingamThreshold runs the Visvalingam-Whyatt algorithm removing
  // triangles whose area is below the threshold. This function is here to simplify the interface.
  // Returns a new path and DOES NOT modify the original.