def center
      center = Vector3.new()
      @vertices.each do |vertex|
        center += vertex
      end
      center /= @vertices.size
      return center
    end
def center
      center = Vector3.new()
      @vertices.each do |vertex|
        center += vertex
      end
      center /= @vertices.size
      return center
    end
[Output]
  return center point as Vector3.