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Nieminen Juha wrote:
>
> Felix Petriconi <fel### [at] ruhr-uni-bochum de> 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
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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.
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>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
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> 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
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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...
/\/\/\//
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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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