我怎样才能在渐近线中绘制 nurbs 曲面的网格线？

Question

对于贝塞尔曲面片，我可以将其定义为曲面并绘制网格线，如示例代码所示：

import three;

size(10cm);
currentlight=Viewport;

surface s=surface(patch(new triple[][] {
  {(0,0,0),(1,0,0),(1,0,0),(2,0,0)},
  {(0,1,0),(1,0,1),(1,0,1),(2,1,0)},
  {(0,1,0),(1,0,-1),(1,0,-1),(2,1,0)},
  {(0,2,0),(1,2,0),(1,2,0),(2,2,0)}}));
//plot surface
draw(s,yellow);
//plot mesh line
draw(s.s[0].vequals(0.5),squarecap+2bp+blue,currentlight);
draw(s.s[0].uequals(0.5),squarecap+2bp+red,currentlight);

我怎样才能对 nurbs 曲面做类似的事情？