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Lance Birch <lan### [at] usa net> wrote in message
news:37c5034d@news.povray.org...
<snip>
> This issue has come up a few times in regard to POV-Ray and it seems there
> is the same problem. POV-Ray isn't a modeller, and modellers are needed
to
> make NURBS surfaces. Making up the keyword description for POV-Ray would
be
> near impossible considering the number of specialised surface triming and
> blend functions along with all the point and CV splines. I personally
have
> no idea how it would be possible to make a tokinised description for
NURBSs.
IIRC Polyray had a NURBS function...
/\/\/\//
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Mike wrote:
> Parsing shouldn't be a problem. The hard part is figuring out how to render the
> surface. This is the example given in the Renderman Interface Specification:
> And you would probably want a trim_curve section inside nurbs_patch. Anyway,
> someone feel like coding this up real quick? ;)
Basing my answer on the knowledge (which there is not a lot of on povray in my
mind as we speak) that povray tesselates everything into triangles before render
time, rendering shouldn't be a problem. All that would be needed is a nurbs
tesselater into the pipeline, i haven't looked at the povray code but wouldn't this
be how the bicubic patches are handled or is it directly rendering the bicubic
surface (not tesselating it).
C.
--
Colin Doncaster
bEnT Animation, Inc.
"Baby Back, Baby Back, Baby Back RIBS!"
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Don't know about the bicubics but apparently the basic primitives are
not (tesselated that is).
Bob
Colin Doncaster <col### [at] bentanimationcom> wrote in message
news:37C59073.90ADBB50@bentanimation.com...
> Basing my answer on the knowledge (which there is not a lot of
on povray in my
> mind as we speak) that povray tesselates everything into triangles
before render
> time, rendering shouldn't be a problem. All that would be needed is
a nurbs
> tesselater into the pipeline, i haven't looked at the povray code
but wouldn't this
> be how the bicubic patches are handled or is it directly rendering
the bicubic
> surface (not tesselating it).
>
> C.
>
> --
> Colin Doncaster
> bEnT Animation, Inc.
>
> "Baby Back, Baby Back, Baby Back RIBS!"
>
>
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Bezier patches are converted to triangles, but the other primitives
aren't.
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TonyB wrote:
>
> > Wha....? I thought bicubic patches *were* a specific subset of NURBs?
> > General NURB support, therefore, would be more flexible, by doing
>
> Sorry, I just want to clear up one thing. NURBS is not plural for NURB.
> NURBS is the acronym for Non-Uniform Rational B-Spline. The correct
> pluralization is NURBSs, no matter how ulgy it sounds.
Oooch, sssss, my Precious.... very well, good maasssster. NURBSs it
isss then. Yesss, indeed, Precious. They modelled it with NURBSs,
they did.(gollum). We thinks they shouldn't haves acronyms ending
in sss, but master sezs, and Smeagol promised to be very good...
yesss...
Smeagol
--
http://www.enter.net/~cfusner
"...Then darkness took me, and I strayed out of thought and time,
and I wandered far on roads that I will not tell..."
-The Two Towers, JRR Tolkien
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On Thu, 26 Aug 1999 19:03:49 -0400, Charles <cfu### [at] enternet> wrote:
>TonyB wrote:
>>
>> > Wha....? I thought bicubic patches *were* a specific subset of NURBs?
>> > General NURB support, therefore, would be more flexible, by doing
>>
>> Sorry, I just want to clear up one thing. NURBS is not plural for NURB.
>> NURBS is the acronym for Non-Uniform Rational B-Spline. The correct
>> pluralization is NURBSs, no matter how ulgy it sounds.
>
>
>Oooch, sssss, my Precious.... very well, good maasssster. NURBSs it
>isss then. Yesss, indeed, Precious. They modelled it with NURBSs,
>they did.(gollum). We thinks they shouldn't haves acronyms ending
>in sss, but master sezs, and Smeagol promised to be very good...
>yesss...
>
>
Would "Non-Uniform Rational B-Spline Thingys" have been much of an
improvement?
Running...
Cheers,
Cliff Bowman
Why not pay my 3D Dr Who site a visit at http://www.who3d.cwc.net/
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> All that would be needed is a nurbs tesselater into the pipeline, i haven't looked
at
> the povray code but wouldn't this be how the bicubic patches are handled or is it
> directly rendering the bicubic surface (not tesselating it).
There is a bicubic type 2 option in the superpatch that pseudo-direct renders. It's
faster than the other methods and uses just a little more memory than type 0. My
understanding is that NURBS can be reduced to bicubic b-spline patches by inserting
knots to make them uniform. I looked into doing this myself but the liturature I've
seen on nurbses is way too complex. Perhaps the problem is trivial if one has the
right resources.
-Mike
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Cliff Bowman wrote:
> Would "Non-Uniform Rational B-Spline Thingys" have been much of an
> improvement?
Heh heh. How about just "Non-Uniform Thingys". Then we could all have
a lovely discussion about the benefits of modelling with NUTs. Or is
that: We nuts could all have a lovely discussion about the benefits
of modelling...
<gd&r>
Charles
--
http://www.enter.net/~cfusner
"...Then darkness took me, and I strayed out of thought and time,
and I wandered far on roads that I will not tell..."
-The Two Towers, JRR Tolkien
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TonyB wrote:
>
> Sorry, I just want to clear up one thing. NURBS is not plural for NURB.
> NURBS is the acronym for Non-Uniform Rational B-Spline. The correct
> pluralization is NURBSs, no matter how ulgy it sounds.
>
<;-)>
The plural of NURBS is NURBSes. The distinction between singular and
plural is thereby audible, and it follows the established convention
followed in such words as "buses" and "gases".
</;-)>
Actually, the convention seems to be to expand NURBS to "Non-Uniform
Rational B-Splines", in which case NURBS is (are?) already plural. In
Piegel & Tiller it's used as a plural.
--
Mark Gordon
mtg### [at] povrayorg
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On Fri, 27 Aug 1999 18:31:47 -0400, Charles <cfu### [at] enternet> wrote:
>Cliff Bowman wrote:
>> Would "Non-Uniform Rational B-Spline Thingys" have been much of an
>> improvement?
>
>Heh heh. How about just "Non-Uniform Thingys". Then we could all have
>a lovely discussion about the benefits of modelling with NUTs. Or is
>that: We nuts could all have a lovely discussion about the benefits
>of modelling...
>
You are Charles Danials and I claim my ten pounds.
In-joke for a completely different group, where he's a character. A
real one.
Anyway - what IS a "Rational B-Spline"? Will it debate the pros and
cons of various techniques to model a specific item, or is in fact not
able to converse rationally?
"Oh no, you don't wanna do that. Sure you can do it with a torus if
you tweak this and that, add a few blobs and cut way that bit over
there - but I'd recommend using B-Splines, I really would".
Cheers,
Cliff Bowman
Why not pay my 3D Dr Who site a visit at http://www.who3d.cwc.net/
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