[CST-2] NURBS circles...

[Raymond Chan]

There are several silly mistakes in my answer below (having been through it
on paper with someone else)... haven't done it again properly but here's a
very brief outline, might write more tomorrow when i'm more awake...

> N[1,1] = 0
> N[2,1] = 0
> N[3,1] = 1, 0<=t<1; 0, otherwise

> N[4,1] = 1, 1<=t<2; 0, otherwise
this should be zero cos of the duplicate t=1 knot, N[5,1] should be that I
think

> N[1,2] = 0
> N[2,2] = 1-t, 0<=t<1; 0, otherwise
> N[3,2] = t, 0<=t<1; (1-t), 1<=t<2; 0, otherwise
>
> N[1,3] = (1-t)t, 0<=t<1; 0, otherwise
> N[2,3] = 2(1-t)t, 0<=t<1; (1-t)^2, 1<=t<2; 0, otherwise
I got some subscripts mixed up in there above (in the working that I haven't
shown), N[1,3] does come out as (1-t)^2 after all

> And why is P(t) from t=0 to 1 when surely it's from
> t[min] = t[k] = 0, to t[max] = t[n+2] = 4 ??

Still don't know the answer to that though

mond