I wrote:
> When looking at wireframes made with nurbs I notice that
> there's almost always a few vital patches with three or
> five corners. And the surface is still completely smooth.
> Is that a special ability nurbs have or what...?

This and the others are questions I've had for a long time and I would
really appreciate if somebody could enlighten me. Do anybody know anything
about it?

Rune
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Rune wrote in message <3b1ab995@news.povray.org>...
>I wrote:
>> When looking at wireframes made with nurbs I notice that
>> there's almost always a few vital patches with three or
>> five corners. And the surface is still completely smooth.
>> Is that a special ability nurbs have or what...?
>
>This and the others are questions I've had for a long time and I would
>really appreciate if somebody could enlighten me. Do anybody know anything
>about it?
>
>Rune

When you have an odd number of corners like that, there will be one or more
patch edges terminating. At that point you will have a discontinuity and a sharp
edge. My research indicates internally, all renderers convert patches to
polygons prior to rendering (possible exception: Hash Animator claims
otherwise). Knowing this most of them make allowances for these discontinuities
and smooth out the result. PoV also converts to triangles but has no method for
automatically smoothing discontinuities like this, apparently treating each
patch as a discrete object without regard for its neighbors within a union, with
any smoothness between patches being the natural result of the continuity
between patches as modeled.

My usual workaround to your problem, is to model without regard to the sharp
edges and then export my patch objects to smooth_triangle mesh objects, which
usually solves my 'smoothing' problems. I usually do this from sPatch, exporting
to .dxf and then several other conversion/processing steps depending on whether
I'm going to bone it for posing (Anim8or) and/or apply UV mapping (UVMapper)
etc.

Since you prefer to hand code, I suggest you look into the capabilities of Chris
Colefax's PCM macros and Warp's mesh compressor. They both support bicubic
patches as well as triangles. You could create your models with all the
complexity you wanted, and animate them the way you wanted, without concern for
smoothness (or lack thereof) and then shell out to the compressor between
frames.

Of course it won't be quite as simple as I've made it sound here, but it is
certainly do-able.

Hope that helps.

----------------------------------------
Batronyx ^"^
bat### [at] cadronhsacom
http://www.batronyx.com
Bhuddist monk to hotdog vendor:
     "Make me one with everything."
----------------------------------------

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Chris Huff <chr### [at] maccom> wrote:
: Not the only drawback...it will use more memory and the lack of adaptive 
: render-time tesselation means you would have more triangles than you 
: needed, or visible faceting.

  Wouldn't render-time tesselation slow it down quite a lot (at least
compared to rendering a triangle mesh)?

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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In article <3b1b53d7@news.povray.org> , Warp <war### [at] tagpovrayorg>  wrote:

>   Wouldn't render-time tesselation slow it down quite a lot (at least
> compared to rendering a triangle mesh)?

Maybe some caching of frequently needed triangles could do.  Not sure how
easy to implement that though...


     Thorsten

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"Batronyx" wrote:
> Since you prefer to hand code, I suggest you look into the
> capabilities of Chris Colefax's PCM macros and Warp's mesh
> compressor. They both support bicubic patches as well as
> triangles.

But they don't convert one format to the other. Nor do they do smoothing.

> You could create your models with all the complexity you
> wanted, and animate them the way you wanted, without
> concern for smoothness (or lack thereof) and then shell out
> to the compressor between frames.

My bicubic patches are written in POV-Ray script and they are dependent on
variables. No program can read that.

Thanks for the information anyway. It answered some of my questions.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated May 10)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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Rune wrote:
> 
> "Batronyx" wrote:
> > Since you prefer to hand code, I suggest you look into the
> > capabilities of Chris Colefax's PCM macros and Warp's mesh
> > compressor. They both support bicubic patches as well as
> > triangles.
> 
> But they don't convert one format to the other. Nor do they do smoothing.

Warp's mesh compressor has a smoothing option.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken <tyl### [at] pacbellnet> wrote:
: Warp's mesh compressor has a smoothing option.

  This is not true, although I have thought about it for quite a long time
(and not implemented it because of laziness, which is partly caused by
the fact that my mesh smoother already does it...).

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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"Ken" wrote:
> Warp's mesh compressor has a smoothing option.

I'm using meshcomp v2.1 and it has no smoothing option as far as I can see.
Which version are you using? Can you copy the part of the manual regarding
the smoothing option?

Not that it would help me anyway, but it's always good to know for future
reference.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated May 10)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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Rune wrote:
> 
> "Ken" wrote:
> > Warp's mesh compressor has a smoothing option.
> 
> I'm using meshcomp v2.1 and it has no smoothing option as far as I can see.

See Warp's reply. My bad.

-- 
Ken Tyler

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In article <3b1b53d7@news.povray.org>, Warp <war### [at] tagpovrayorg> 
wrote:

>   Wouldn't render-time tesselation slow it down quite a lot (at least
> compared to rendering a triangle mesh)?

It would be slower but save memory...you would have a choice, just like 
you do with bicubic patches.

-- 
Christopher James Huff - chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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