位置
(2t³ - 3t² + 1) * p0 + (t³ - 2t² + t) * m0 + (-2t³ + 3t²) * p1 + (t³ - t²) * m1
切线
p‘(t) = (6t² - 6t)p0 + (3t² - 4t + 1)m0 + (-6t² + 6t)p1 + (3t² - 2t)m1
http://www.cnblogs.com/jqm304775992/p/5044728.html
原文：https://www.cnblogs.com/lilei9110/p/10053509.html