POV-Ray : Newsgroups : povray.binaries.images : Almost Sphere Spirals (109 KB) Server Time
28 Mar 2024 13:51:53 EDT (-0400)
  Almost Sphere Spirals (109 KB) (Message 11 to 20 of 24)  
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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 26 Jan 2002 09:37:06
Message: <3C52BE54.B91AC28A@hotmail.com>
Bill DeWitt wrote:
> 
>     All it needs is a guy looking up at it. Make him so small that he can be
> mistaken for a spot, then you notice the shadow and the scale suddenly
> shifts...

Thank you for the idea Bill. I'm thinking
about how where I can get a human model from.


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 26 Jan 2002 09:39:57
Message: <3C52BEFE.346A4C0A@hotmail.com>

> 
> Fantastic, I like the image just as it is.
> 
> Congratulations,

I'm very glad you like it Fernando.

Thank you.


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 26 Jan 2002 10:00:56
Message: <3C52C3E7.264794C2@hotmail.com>
Gleb wrote:
> 
> Looks nice.

Thanks.


> Will it form a whole sphere when combined
> 
> with the y-rotated other textured one?

No. I'm sorry if the title of my prior
posts have confused you people.

This shape uses another PhiFn() than the one
I used for the shape in my "The remains of an
iso sphere: Take 2" image. 

I think that I'll soon post some source code
for this image to p.t.s-f.


Tor Olav


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From: Txemi Jendrix
Subject: Re: Almost ... Iso carpet
Date: 26 Jan 2002 10:01:21
Message: <3c52c4c1@news.povray.org>

news:3c526337@news.povray.org...
> Yes, it is caused by the syntax change.  I posted the revised one
> in p.t.s-f as a reply of that message.  (I've added checker and hexagon
> pattern in that scene)  I hope it is helpful for your project.

Wow!
Thank you very much.
Bye.
--
Txemi Jendrix
tji### [at] euskalnetnet
http://www.geocities.com/txemijendrix


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From: Ryan Mooney
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 27 Jan 2002 13:10:27
Message: <3C544294.A02EFA5C@earthlink.net>
that would be great i would like to see the texture details... =]

Tor Olav Kristensen wrote:

> Gleb wrote:
> >
> > Looks nice.
>
> Thanks.
>
> > Will it form a whole sphere when combined
> >
> > with the y-rotated other textured one?
>
> No. I'm sorry if the title of my prior
> posts have confused you people.
>
> This shape uses another PhiFn() than the one
> I used for the shape in my "The remains of an
> iso sphere: Take 2" image.
>
> I think that I'll soon post some source code
> for this image to p.t.s-f.
>
> Tor Olav


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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 27 Jan 2002 20:32:16
Message: <3C54A942.617AD2B5@online.no>
Tor Olav Kristensen wrote:
>...
> (Because there seems to be some
> calculations that are not calculated
> correctly by POV-Ray. Increasing
> max_gradient or accuracy did not help
> at all.)
>...

Attached are two images that shows
the defect in the shape.

IIRC Riemann16_s1.jpg was rendered with the
max_gradient set to 4 and for Riemann16_s2.jpg
it was set to 250.

(The images was rendered at different
resolutions and with different light settings.)

I find the "tongue" that appears in the _s2
image quite mysterious.


Tor Olav


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Attachments:
Download 'riemann16_s1.jpg' (13 KB) Download 'riemann16_s2.jpg' (5 KB)

Preview of image 'riemann16_s1.jpg'
riemann16_s1.jpg

Preview of image 'riemann16_s2.jpg'
riemann16_s2.jpg


 

From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 27 Jan 2002 20:43:07
Message: <3C54ABD4.95EB6DCA@online.no>
Christoph Hormann wrote:
>...
> If that surface structure is a normal you could make it part of the
> isosurface geometry.  Apart from that, do you have 'normal on' in
> radiosity?

I didn't think of that. Now I have started experimenting
with that. Thank you for the suggestion.

And yes, I had the normal on in radiosity.

>...
> > I should probably mention that I had
> > to "hand correct" the finished image
> > somewhat at the sphere's "south pole".
> >
> > (Because there seems to be some
> > calculations that are not calculated
> > correctly by POV-Ray. Increasing
> > max_gradient or accuracy did not help
> > at all.)
> 
> I think it's quite obvious that spiral structures lead to infinite
> gradients which can't be rendered correctly under all circumstances.

Yes that was my first thought too.

But as this shape is symmetric around both
its x and z axes (as Anton Sherwood mentioned
too), there should be infinite gradients at
the opposite pole as well.

But I have not experienced any problems at
that pole yet.


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 27 Jan 2002 20:59:09
Message: <3C54AF97.66DDFC9C@hotmail.com>
Anton Sherwood wrote:
> 
> Tor Olav:
> > > (Because there seems to be some
> > > calculations that are not calculated
> > > correctly by POV-Ray. Increasing
> > > max_gradient or accuracy did not help
> > > at all.)
> 
> Slime:
> > If you defined the spiral correctly, that's because the spiral
> > never ends, the detail increases towards the poles infinitely.
> > That is, if I understood the description of the shape that I
> > read a while ago correctly.
> 
> In an equiangular spiral (reverse Mercator projection of oblique
> parallels), that would happen at both poles; TOK said only one.

I don't remember what reverse Mercator projection is,
so I don't quite get what you are saying here.

But I guess that you are thinking the same as me:
That the problem should surface at the other pole as
well, because the gradients should be symmetric too.

 
> What's the formula?

I have posted the source to povray.text.scene-files now:

http://news.povray.org/povray.text.scene-files/21784/
news://news.povray.org/3C549C14.A9009E4%40online.no


> (Love the textures.)

I just modified one that Gilles Tran once made.
"Radiosity test #2", Aug 2000:

http://news.povray.org/search/?s=Radiosity+test+%232&b=Search


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 27 Jan 2002 21:05:24
Message: <3C54B10F.6C11F8A8@hotmail.com>
"R. Suzuki" wrote:
> 
> "Tor Olav Kristensen" wrote in message
> > I'm not sure if this image is finished
> > or not now.
> >
> > What do you think ?
> 
> Nice image.

Thank you.


> > I should probably mention that I had
> > to "hand correct" the finished image
> > somewhat at the sphere's "south pole".
> >
> > (Because there seems to be some
> > calculations that are not calculated
> > correctly by POV-Ray. Increasing
> > max_gradient or accuracy did not help
> > at all.)
> 
> I tried to render your scene file posted in p.t.s-f
> last month.  But I could not find any problem
> on the image.  Did you use the same function?


You are right: The last scene file did not
produce any errors in the image.

For this image a used a different function
for the rotation. See my recent post to
povray.text.scene-files for the source code:

http://news.povray.org/povray.text.scene-files/21784/
news://news.povray.org/3C549C14.A9009E4%40online.no


Tor Olav


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From: Alf Peake
Subject: Re: Almost Sphere Spirals (109 KB)
Date: 28 Jan 2002 11:08:18
Message: <3c557772@news.povray.org>
"Tor Olav Kristensen" <tor### [at] onlineno> wrote in message
news:3C54A942.617AD2B5@online.no...
[snip]
> Attached are two images that shows
> the defect in the shape.
>
> I find the "tongue" that appears in the _s2
> image quite mysterious.
>
>
> Tor Olav

Perhaps this defect is only on the inner surfaces so the upper pole
looks OK from outside?

Alf


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