/// <summary>
 /// 获取边起点到终点的长度
 /// </summary>
 /// <param name="edge"></param>
 /// <returns></returns>
 /// <remarks>非直线的话不可以使用此长度</remarks>
 public static double GetVectorLength(this IEdge edge)
 {
     return(edge.GetEdge3().Delta.Length());
 }