Am 04.08.2015 um 18:11 schrieb LanuHum:

>> POV-Ray doesn't support NURBS (non-uniform rational B-splines).
>
> Thanks!
> There is no support of nurbs, there is no support of bezier (an exception of
> lathe and prism). Refusal of nurbs and bezier is a concept?

Bezier splines are just a special case of cubic splines, differing only 
in how the control points are translated into the coefficients for the 
polynomials used in the background.

Missing support for bezier in spline functions and sphere_sweep is just 
a matter of incomplete implementation, not of a philosophy.


One reason (the primary one in my book) for missing NURBS support has 
been the lack of affordable user interfaces to define NURBS surfaces and 
export the coefficients to a format suitable for POV-Ray. I wouldn't 
want to have to input NURBS coefficients directly to test such a 
feature, especially if I have no way of verifying the resulting shape.

I didn't know Blender supported NURBS surfaces. If it does, you could 
help by providing a very basic export function that just writes the 
coefficients to an array.

I only have a rudimentary understanding of the underlying math though, 
and there's other stuff high on my agenda at present, so don't hold your 
breath unless Jerome is willing to pick up the glove.

@Jerome: Even if the implementation would be similar to that of bicubic 
patch type 1, i.e. an internal translation to something mesh-like, so 
that in a sense the whole job could also be done by the exporter by 
generating a mesh2 object, I think a NURBS primitive would be beneficial 
in order to minimize file I/O in the workflow.


> If I wrote the AutodeskMaya2Povray exporter, I would meet the same problems?
> :(

I don't think so. I'm pretty sure Maya provides mechanisms for export 
filters to access mesh representations of NURBS surfaces rather than the 
NURBS coefficients themselves, so that would be an option.

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