#http://xuxzmail.blog.163.com/blog/static/25131916200961311531402/
#猴鞍面  （Monkey saddle） 是数学家为猴子量身定做的一种鞍面

vertices = dimension1:320 dimension2:320

x = from (-2) to (2) dimension1
z = from (-2) to (2) dimension2

y = x*(x*x - 3*z*z)