Yep, real nurbs, without tesselation.

(and nurbs also mean b-spline, as b-spline are nurbs with weight = 1 everywhere).

Short of transforming a square section into a circular section, it's hard to see a
manual application for it, but some people might have a modeler to generate them.

It's a 2D finite object.

Syntax is :

nurbs { u_size, v_size [accuracy a_value]

 followed by the u_vsize*v_size 4D vectors (fourth coordinates is the weight, which
must not be negative),
as first line for v, second line for v and so on.

Minimal value for v_size and u_size is 2. The max value is up to your patience and
memory, as more points mean slowing down the render.

uv_mapping and clipped_by are supported.

And now for the good & bad news: this is not supported in hgpovray, but on my master
branch (because the rewrite of the code in the official master branch made it easier
to deals with the involved maths).

==== [Rendering...] ========================================================
Rendered 1228800 of 1228800 pixels (100%)
----------------------------------------------------------------------------
Render Statistics
Image Resolution 1280 x 960
----------------------------------------------------------------------------
Pixels:          1305600   Samples:          461097   Smpls/Pxl: 0.35
Rays:            1766697   Saved:                 0   Max Level: 1/10
----------------------------------------------------------------------------
Ray->Shape Intersection          Tests       Succeeded  Percentage
----------------------------------------------------------------------------
Box                             307149           45020     14.66
Cone/Cylinder                   178476           41510     23.26
Nurbs                          7234487         1006956     13.92
Bounding Box                  21742788        10255503     47.17
----------------------------------------------------------------------------
Shadow Ray Tests:           1760307   Succeeded:                139322
Shadow Cache Hits:           139038
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Render Time:
  Photon Time:      No photons
  Radiosity Time:   No radiosity
  Trace Time:       0 hours  0 minutes 56 seconds (56.541 seconds)
              using 12 thread(s) with 610.511 CPU-seconds total
POV-Ray finished

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