Hallo,

are there any plans to include NURBS into PovRay?

I think it would be a great advantage to have NURBS in PovRay because
You would not have to handle big meshes.

I know it is not so easy to implement this feature because it is
mathematicaly
a little bit tricky. But I believe that the time consuming ray-testing
AND reading
of big meshes would be history with this feature.

(I have worked with BMRT, which supports the NURBS, and it was really
nice
to render quite complicated modells.)
By the way, some of the great modellers (like Rhino) support NURBS.


I just wanted to start a discussion. Perhaps there are some good reasons
not
to include NURBS into PovRay.

Greetings,

Felix

Post a reply to this message

What are the advantages of NURBS (or should I say NURBSes?) over bicubic
pathces?

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

Post a reply to this message

Hi all!

Funny you should mention this.  I've been working on molding a 3Com Ethernet
card as closely as possible.  The first images are posted in the p.b.i.
group.  Everything is being modeled using Rhino, piece by piece, positioned
and textured in Moray, then finally rendered in POV-Ray.  The only things I
have done so far are the board, bracket, all screws, activity LED, the
complete AUI connector, and the AUI connector lock.  I still have to do the
Twisted Pair connector and board components as well as the board traces and
writing.  (The last two I don't have any idea how I'm going to do yet!)

Anyway, I guess it would be a good thing to include NURBS support (although
it would probably cause the POV-Team to start charging for POV-Ray!)
Currently the pieces are exported to Moray using Moray's UDO/INC.  This
generates mesh files of pretty considerable size and complexity.  All
objects currently total about 49MB.  Guess which piece generated to biggest
file (by far!).  Like I said, I still have alot of work to do and I estimate
that the total size is going to be around 125MB in exported files.

The stats on the POV rendered models so far include:

    640 x 480, Alias 1 adaptive, No Radiosity
    Peak memory used:  38MB
    Time to parse:   0h 13m
    Time to trace:    2h 38m


Felix Petriconi <fel### [at] ruhr-uni-bochumde> wrote in message
news:37C3EE28.C51EB041@ruhr-uni-bochum.de...
> Hallo,
>
> are there any plans to include NURBS into PovRay?
>
> I think it would be a great advantage to have NURBS in PovRay because
> You would not have to handle big meshes.
>
> I know it is not so easy to implement this feature because it is
> mathematicaly
> a little bit tricky. But I believe that the time consuming ray-testing
> AND reading
> of big meshes would be history with this feature.
>
> (I have worked with BMRT, which supports the NURBS, and it was really
> nice
> to render quite complicated modells.)
> By the way, some of the great modellers (like Rhino) support NURBS.
>
>
> I just wanted to start a discussion. Perhaps there are some good reasons
> not
> to include NURBS into PovRay.
>
> Greetings,
>
> Felix
>

Post a reply to this message

Felix Petriconi wrote:
> 
> Hallo,
> 
> are there any plans to include NURBS into PovRay?
> 
> I think it would be a great advantage to have NURBS in PovRay because
> You would not have to handle big meshes.
> 
> I know it is not so easy to implement this feature because it is
> mathematicaly
> a little bit tricky. But I believe that the time consuming ray-testing
> AND reading
> of big meshes would be history with this feature.
> 
> (I have worked with BMRT, which supports the NURBS, and it was really
> nice
> to render quite complicated modells.)
> By the way, some of the great modellers (like Rhino) support NURBS.
> 
> I just wanted to start a discussion. Perhaps there are some good reasons
> not
> to include NURBS into PovRay.
> 
> Greetings,
> 
> Felix

Well, for discussion you can search this very same newsgroup for NURBS
in subject. There is at least 4 threads with quite smart names as "NURBS
support", "NURBS patch", "NURBS...", "NURBS?". This will give quite good
overview of opinions. Seems like this subject will be good candidate for
FAQ (or VFAQ, how about it, Warp?).

Post a reply to this message

Hi again,

Nieminen Juha wrote:

> What are the advantages of NURBS (or should I say NURBSes?) over bicubic
pathces?

I did not know that there are bicubic patches. I read then the documentation
of the current
PovRay version. There is mentioned:

"Like triangles, the bicubic patch is not meant to be generated by hand. These
shapes should be created by a special utility. You may be able to acquire
utilities to generate these shapes from the same source from which you
obtained POV-Ray."

My next step was to search for such a utility on the PovRay homepage. I just
found the program
breeze designer, which seems that there is no further development since 1996.

Are there other tools or programs wich support the possibility to export
bicubic patches into
PovRay format?

Nieminen, You asked for the advantages of NURBS. I do not know the maths but
there have to be a reason,
that proffessional programs like Maya, Houdini and others support NURBS. (This
might not be
the best argumentation, but it supports a little bit that NURBS have
advantages against bicubic patches.

Greetings, Felix

Post a reply to this message

BTW, Felix, your computer's timezone seems to be wrong by one hour
(shouldn't it be +2000 for Germany??). Juha's response is before your
question!

Post a reply to this message

Felix Petriconi wrote:
> Are there other tools or programs wich support the possibility to export
> bicubic patches into PovRay format?

SPatch is the preferred utility of many people and is highly capable.
http://www.cableone.net/alyson/spatch.html
 
> Nieminen, You asked for the advantages of NURBS. I do not know the maths
> but  there have to be a reason, that proffessional programs like Maya,
> Houdini and others support NURBS. (This might not be the best argument,
> but it supports a little bit that NURBS have advantages against bicubic
> patches. Greetings, Felix

I think one of the main advantages with nurbs is that the format is good for
modelling complex shapes with inside of a modelling environment. Since pov
has no direct nurb manipulation capabilities, and it is not a modeller, it
is just as easy to represent the final modelled shape with simple triangles.
There is no real difference in the final raytraced image no matter which
method is used and there would be a large overhead to adding nurbs support
to Povray.

I am not well informed where nurbs are concerned and what I have said may
be wrong.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

Post a reply to this message

Ken wrote:

> Felix Petriconi wrote:
> > Are there other tools or programs wich support the possibility to export
> > bicubic patches into PovRay format?
>
> SPatch is the preferred utility of many people and is highly capable.
> http://www.cableone.net/alyson/spatch.html

Thanks for the information!

> [..]
> I think one of the main advantages with nurbs is that the format is good for
> modelling complex shapes with inside of a modelling environment. Since pov
> has no direct nurb manipulation capabilities, and it is not a modeller, it
> is just as easy to represent the final modelled shape with simple triangles.
> There is no real difference in the final raytraced image no matter which
> method is used and there would be a large overhead to adding nurbs support
> to Povray.

Yes, the representation might be easyer with triangles, but the files with the
triangles might be a little bit bigger than the nurbs description. Once I
created
a TIE fighter with Rhino. The size was about 12 MB. The PovRay meshfile
was about 125 MB and it took some time to parse it. (I know that there is
a utility by Chris Colefax which reduces the number of triangles.)

Greetings Felix

Post a reply to this message

Felix Petriconi wrote:

> Yes, the representation might be easyer with triangles, but the files with the
> triangles might be a little bit bigger than the nurbs description. Once I
> created
> a TIE fighter with Rhino. The size was about 12 MB. The PovRay meshfile
> was about 125 MB and it took some time to parse it. (I know that there is
> a utility by Chris Colefax which reduces the number of triangles.)
> 
> Greetings Felix

One thing I have heard other Rhino users mention is that when exporting
the file to pov format they first do a triangle count reduction. If you
use smooth triangles in Pov you don't need nearly the number of triangles
you would need to see a smooth surface anyway. You can probably reduce
your triangle count considerably and still have a good looking model.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

Post a reply to this message

Felix Petriconi wrote:
> Once I created
> a TIE fighter with Rhino. The size was about 12 MB. The PovRay meshfile
> was about 125 MB and it took some time to parse it. (I know that there is
> a utility by Chris Colefax which reduces the number of triangles.)
> 
> Greetings Felix

Felix, in order to use Rhino with POVRay I'd suggest to export from
Rhino to 3DS format, then use 3DS2POV converter to create files with
mesh2 format, which will be much more compact and will retain UV mapping
information. In order to use mesh2 format, you have to use either
Superpath or UV patched POVRay.

Post a reply to this message

All I have to say is I paid $200 for Hash animation Master and wrote a plugin
for it that can export POV-Ray bicubic patches.  Simple and easy. :)

One thing I've noticed is that NURBS appears to have been a fad.  They can
accurately represent some objects that bezier patches cannot, yet from an
artistic point of view there is no real advantage.  The latest thing is
subdivsion surfaces;  NURBS are yesterday's news (if you buy into that malarchy)

-Mike

Post a reply to this message

>   What are the advantages of NURBS (or should I say NURBSes?) over
>  bicubic pathces?

Wha....? I thought bicubic patches *were* a specific subset of NURBs?
General NURB support, therefore, would be more flexible, by doing
anything a patch can do but being more adaptable? Wouldn't it? Okay,
If I'm wrong, blame it on being tired. I shouldn't be allowed near
a keyboard when I'm tired. 

As to the matter of smaller file size... yeah, guess so, although I'd
be more concerned with render-time memory savings than stored file
sizes. Bezier patches, if I remember rightly, have (or at least had?)
an option to choose between patch types that preprocessed to triangles
or on-the-fly control point calculations. This traded off memory size
for computation speed depending on your needs. I imagine if 
generalized NURBs were implemented, it would have similar options. 
Nowadays, with faster processors, computations speed would probably
be less of a concern than available memory with huge models. Could 
be nice in that case.


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

Post a reply to this message

> 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.

--
Anthony L. Bennett
http://welcome.to/TonyB

Non nova, sed nove.

Post a reply to this message

Felix Petriconi <fel### [at] ruhr-uni-bochumde> wrote:
: (I know that there is
: a utility by Chris Colefax which reduces the number of triangles.)

  If you are talking about the triangle mesh compressor, two points:
  1) It doesn't reduce the number of triangles, it just stores them in a
more compact format.
  2) The macro by Chris just reads the compressed data into povray (and
creates the mesh), it doesn't generate it.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

Post a reply to this message

Vahur Krouverk <vah### [at] fvaetecee> wrote:
: Seems like this subject will be good candidate for
: FAQ (or VFAQ, how about it, Warp?).

  I can add it if someone gives me a question and an answer (which should be
comprehensive and correct).

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

Post a reply to this message

Well, it depends what you're doing.

The main advantage I find in using NURBSs is adaptive generation and
degradation of the final rendered mesh and also vastly more modelling
methods compared to patches.  A good example of the AG/D of NURBSs is when
using really complex models.  If you render the model based on mesh patches
you could end up with a massive amount of triangles.  With NURBS models you
can simply set the restraint angles and distances so it adaptively generates
the surface.

The other thing as I mentioned was the flexibility of modelling.  For
example with NURBSs it's very easy to just trim up and blend two surfaces
together seemlessly.

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.

Someone also mentioned subdivision surfaces.  This has become an offshoot of
NURBS modelling and uses a method called "soft selections" (the term changes
from modeller to modeller).  Basically it works the same way only it allows
you to add weights to all NURBS points (even if it's a CV spline).  While
NURBSs already support this, subdivision surfaces do it differently because
they work on existing models (they "subdivide" <- thus the name; the
surface).

Anyway, I think I said this the last time the NURBS issue came up:  NURBSs
would be near impossible to impliment into POV-Ray and considering the
computational and programming overheads, it really isn't worth it.

Anyway, back to work, just thought I'd stop in.

--
Lance.


---
For the latest 3D Studio MAX plug-ins, images and much more, go to:
The Zone - http://come.to/the.zone
For a totally different experience, visit my Chroma Key Website:
Colorblind - http://listen.to/colorblind
Nieminen Juha wrote in message <37c3e249@news.povray.org>...
>  What are the advantages of NURBS (or should I say NURBSes?) over bicubic
>pathces?
>
>--
>main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
>):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

Post a reply to this message

Nieminen Juha wrote:
> 
> Felix Petriconi <fel### [at] ruhr-uni-bochumde> wrote:
> : (I know that there is
> : a utility by Chris Colefax which reduces the number of triangles.)
> 
>   If you are talking about the triangle mesh compressor, two points:
>   1) It doesn't reduce the number of triangles, it just stores them in a
> more compact format.
>   2) The macro by Chris just reads the compressed data into povray (and
> creates the mesh), it doesn't generate it.

It should also be noted that the mesh compressor utility while reducing
file sizes also has a minor disadvantage of increasing parsing times and
adds a bit of overhead to the memory usage of the program. I have not found
it considerable enough to worry about yet but with extremely large mesh
files this extra burden could exceed your memory capabilities.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

Post a reply to this message

Lance Birch wrote:
> 
> Well, it depends what you're doing.
> 
> 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.  

The same could be said about bicubic patches, and all we need is tools
to generate them (SPatch, Moray,...).  Same apply for NURBS.  If they
get implemented, they will work as patches work : subdivided into smooth
triangles before the rendering.

>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.

The Renderman specifications include NURBS.  RIB files are just text
files,
so it's perfectly possible to have such an implementation in Pov.  BMRT
is
also a-renderer-not-a-modeler and uses NURBS (and much probably
subdivides
them into small triangles before rendering).

Fabien.

Post a reply to this message

>The same could be said about bicubic patches, and all we need is tools
>to generate them (SPatch, Moray,...).  Same apply for NURBS.  If they

Good point actually... but NURBS are much more complex.  I don't see a
problem in normal surface generation but if you want to impliment full point
and CV spline -> surface generation things could get tricky.

>The Renderman specifications include NURBS.  RIB files are just text
>files,

It's also a rather large renderer :)  It's not impossible, just a lot of
work.  If someone is willing to work out the spacial and/or
normalised-tension surface generation, by all means :)  I just thought that
maybe the POV-Team might wish to work on media or something like that at the
moment rather than trying to impliment NURBS which would be a rather large
thing to do.

Some interesting ideas though, maybe similar specifications to RIB could be
used in the parsing of NURBSs (the keywords that is).

--
Lance.


---
For the latest 3D Studio MAX plug-ins, images and much more, go to:
The Zone - http://come.to/the.zone
For a totally different experience, visit my Chroma Key Website:
Colorblind - http://listen.to/colorblind

Post a reply to this message

> Some interesting ideas though, maybe similar specifications to RIB could be
> used in the parsing of NURBSs (the keywords that is).

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:

RIB BINDING

        NuPatch nu uorder uknot umin umax nv vorder vknot vmin vmax
parameterlist

EXAMPLE

        NuPatch 9 3 [ 0 0 0 1 1 2 2 3 3 4 4 4 ] 0 4
        2 2 [ 0 0 1 1 ] 0 1
        "Pw" [   1  0  0 1  1  1  0 1  0  2  0 2
                -1  1  0 1 -1  0  0 1 -1 -1  0 1
                 0 -2  0 2  1 -1  0 1  1  0  0 1
                 1  0 -3 1  1  1 -3 1  0  2 -6 2
                -1  1 -3 1 -1  0 -3 1 -1 -1 -3 1
                 0 -2 -6 2  1 -1 -3 1  1  0 -3 1 ]

The hardest part of deciding on a POV-Ray interpretation is keeping it compact.
My quick idea:

nurbs_patch {
points <u, v> order <u, v> u_knot {} v_knot {} range <u_min, v_min>, <u_max,
v_max>
control_points {}
}

nurbs_patch {
points <9, 2>
order <3, 2>
u_knot {0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 4}
v_knot {0, 0, 1, 1}
range {<0, 2>, <4, 2>
control_points {
<1, 0, 0, 1>, <1, 1, 0, 1>, <0, 2, 0, 2>,
<-1, 1, 0, 1>, <-1, 0, 0, 1>, <-1, -1, 0, 1>,
<0, -2, 0, 2>, <1, -1, 0, 1>, <1, 0, 01>,
<1, 0, -3, 1>, <1, 1, -3, 1>, <0, 2, -6, 2>,
<-1, 1, -3, 1>, <-1, 0, -3, 1>, <-1, -1, -3, 1>,
<0, -2, -6, 2>, <1, -1, -3, 1>, <1, 0, -3, 1>
}

}

And you would probably want a trim_curve section inside nurbs_patch.  Anyway,
someone feel like coding this up real quick? ;)

-Mike

Post a reply to this message

Lance Birch <lan### [at] usanet> 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...

/\/\/\//

Post a reply to this message

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!"

Post a reply to this message

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!"
>
>

Post a reply to this message

Bezier patches are converted to triangles, but the other primitives
aren't.

Post a reply to this message

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

Post a reply to this message

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/

Post a reply to this message

> 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

Post a reply to this message

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

Post a reply to this message

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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> 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?

I think it has something to do with weights.  Each point has a weight that
controls the shape of the spline.  If the weights of all the points is
increased the line will not change.*

-Mike

*Disclaimer - some or all of this may very well be completely wrong.

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Cliff Bowman wrote in message <37cac361.90304208@news.povray.org>...
>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?
>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?


Personally, I prefer my B-Splines to be irrational.

Mark

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Nieminen Juha wrote:
>  What are the advantages of NURBS (or should I say NURBSes?) over bicubic
>pathces?
>
>--
>main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
>):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
>

I am not sure where this should be posted because this thread has taken a
number of turns.

NURBS have an advantage of being used in a number of good programs.
(Rhino3D)

If NURBS are to be added to POVRay I thank thay should be rendered directly
like the other primitives. Bicubic patches seem odd in that they are not
rendered directly.  They have a problem of showing gapes and holes because
of this. POVRay is strong because it uses objects based on math. NURBS can
be rendered directly and would produce very detailed results.


I am not sure how this will be taken but some objects like NURBS could be
external objects included like images and rendered. This could also be used
with other formats like 3DS and LWO.

#declareEXTOBJ MYLWO =  "My object.lwo";

#MYLWO{translate x*10}

For NURBS this could be done useing the openNURBS provided by Rhino3D

Sub-Parts could be accessed like properties in object oriented programming
or like the color components of a pigment used in a function.

#MY3DM.wheel.texture = MY_POV_TEXTURE;

Not sure how that would work but the idea should be simple.

As for which is better between SubDivision and NURBS I really think they
each have their uses. Sometimes it is hard to model with subdivision
somthing that NURBS does easy. It goes the other way also.

Am I way out for POVRay here?

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in news:web.3ffc330de3854bcb4e1f4eb10@news.povray.org m1j wrote:

> Am I way out for POVRay here?
> 

Kind off ..... you replied to a post that is some 3,5 years old :)


Ingo

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"ingo" <ing### [at] tagpovrayorg> wrote in message
news:Xns### [at] netplexaussieorg...

>
> Kind off ..... you replied to a post that is some 3,5 years old :)

Heh - that "Nieminen Juha wrote:" threw me for a minute....

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On 7 Jan 2004 12:21:53 -0500 ingo wrote:

>Kind off ..... you replied to a post that is some 3,5 years old :)

  Wow, I retrieved Warp's original (referenced) post and the thread
moved to the top of my displayed messages in this group ;)

-- 
Alan
ako### [at] povrayorg
a k o n g <at> p o v r a y <dot> o r g

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