Surface with Frenet frame
I tried to draw a surface along a curve,by using Frenet curve.
In the file you can see I draw a curve c on plane,
and use unitvector(perpendicularvector(c'(t))) and (0,0,1) as Frenet frame to draw circles at each point to construct a surface named h(t,s),
But you can see that unitvector(perpendicularvector(c'(t))) didn't work well.
In another way, I use curve command to script this circles p(s), it works .
So I want to know how to fix this problem or is this a bug ?
Thank you for taking time to read this.