public void DirToTest()
{
Point3D point = new Point3D()
{
X = 0, Y = 0, Z = 0
};
var result1 = point.DirTo(null);
Assert.AreEqual(result1, 0);
Point3D endPoint = new Point3D()
{
X = 1, Y = 1, Z = 1
};
var result2 = point.DirTo(endPoint);
Assert.AreEqual(result2, 45 * Math.PI / 180); //包括Z轴
}
