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30 Jun 2022 12:10:41 EDT (-0400)
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From: Craig Lindley
Subject: Help With Image
Date: 29 Mar 2022 14:55:00
Message: <web.624355ce1279d6892f73d2b2bc520638@news.povray.org>
Hello,

I came across the attached image the other day that I thought was beautiful so I
decided to look at raytracing again. I hadn't done any raytracing since about
1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
in the 1990's and today on my Mac it took about 10 minutes.

Anyway. I would like to understand how this image was produced because I would
like to do something like it for this years Christmas card.

It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
POVRAY documentation for these types of spirals but I cannot seem to duplicate
the image accurately. I would guess that each color is its own Fibonacci spiral
but how they are positioned so they don't interfere with each other escapes me.

Any help or suggestions would be appreciated. If anyone has access to the actual
POV file for this image I would love to have it.

Thanks in advance.


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Attachments:
Download 'spiral_geometry_infinity_gimp_sphere_creativecommons_math_doyle-928205.jpg!d.jpe.jpg' (527 KB)

Preview of image 'spiral_geometry_infinity_gimp_sphere_creativecommons_math_doyle-928205.jpg!d.jpe.jpg'
spiral_geometry_infinity_gimp_sphere_creativecommons_math_doyle-928205.jpg!d.jpe.jpg


 

From: Bald Eagle
Subject: Re: Help With Image
Date: 29 Mar 2022 15:20:00
Message: <web.62435b002a8c6bc61f9dae3025979125@news.povray.org>
"Craig Lindley" <cal### [at] gmailcom> wrote:
> Hello,
>
> I came across the attached image the other day that I thought was beautiful so I
> decided to look at raytracing again. I hadn't done any raytracing since about
> 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> in the 1990's and today on my Mac it took about 10 minutes.
>
> Anyway. I would like to understand how this image was produced because I would
> like to do something like it for this years Christmas card.
>
> It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> POVRAY documentation for these types of spirals but I cannot seem to duplicate
> the image accurately. I would guess that each color is its own Fibonacci spiral
> but how they are positioned so they don't interfere with each other escapes me.
>
> Any help or suggestions would be appreciated. If anyone has access to the actual
> POV file for this image I would love to have it.
>
> Thanks in advance.

Welcome back to POV-Ray and raytracing.  :)

Well - they are spirals, whether or not they are Fibonacci or Golden spirals or
logarithmic or Archimedean spirals is anyone's guess.

Get yourself an equation or algorithm for a spiral and make the first one - NOT
starting at the origin, but a bit off to the +x side.
Then you can either generate a new spiral starting with a sphere that's first
rotated around the origin a bit, or just generate the same spiral as a union,
and rotate the whole thing.
I'd start by just drawing a circle, and based on the fact that you can go once
around a circle with 6 of its radii, then you can do some basic geometry/algebra
and figure out what the diameter of each sphere should be if their centers lie
on a given circle.
Step out away from the origin and figure out a second circle that have spheres
that will be tangent to the first, and you'll likely be able to come up with an
algorithm or formula to iterate out.


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From: Tor Olav Kristensen
Subject: Re: Help With Image
Date: 29 Mar 2022 18:55:00
Message: <web.62438dfb2a8c6bc66d7cc5a589db30a9@news.povray.org>
"Craig Lindley" <cal### [at] gmailcom> wrote:
> Hello,
>
> I came across the attached image the other day that I thought was beautiful so I
> decided to look at raytracing again. I hadn't done any raytracing since about
> 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> in the 1990's and today on my Mac it took about 10 minutes.
>
> Anyway. I would like to understand how this image was produced because I would
> like to do something like it for this years Christmas card.
>
> It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> POVRAY documentation for these types of spirals but I cannot seem to duplicate
> the image accurately. I would guess that each color is its own Fibonacci spiral
> but how they are positioned so they don't interfere with each other escapes me.
>
> Any help or suggestions would be appreciated. If anyone has access to the actual
> POV file for this image I would love to have it.
>
> Thanks in advance.

Hi Craig

Perhaps you can find some useful information by doing this search:
https://www.google.com/search?q=Doyle+spiral+circle&tbm=isch

In my opinion those Doyle spirals looks very similar to those in that image.

--
Tor Olav
http://subcube.com
https://github.com/t-o-k


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From: David Buck
Subject: Re: Help With Image
Date: 29 Mar 2022 19:14:49
Message: <624392e9$1@news.povray.org>
Hey, Craig.  I haven't seen you around in years.

For those who don't know, Craig is the author of Practical Raytracing in C:
	"https://www.amazon.ca/Practical-Ray-Tracing-Craig-Lindley/dp/0471573019"

(unless I have the wrong Craig Lindley  :-)  )

David Buck


On 2022-03-29 2:54 p.m., Craig Lindley wrote:
> Hello,
> 
> I came across the attached image the other day that I thought was beautiful so I
> decided to look at raytracing again. I hadn't done any raytracing since about
> 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> in the 1990's and today on my Mac it took about 10 minutes.
> 
> Anyway. I would like to understand how this image was produced because I would
> like to do something like it for this years Christmas card.
> 
> It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> POVRAY documentation for these types of spirals but I cannot seem to duplicate
> the image accurately. I would guess that each color is its own Fibonacci spiral
> but how they are positioned so they don't interfere with each other escapes me.
> 
> Any help or suggestions would be appreciated. If anyone has access to the actual
> POV file for this image I would love to have it.
> 
> Thanks in advance.


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From: Robert McGregor
Subject: Re: Help With Image
Date: 29 Mar 2022 23:50:00
Message: <web.6243d23e2a8c6bc687570eabd4644d08@news.povray.org>
David Buck <dav### [at] simberoncom> wrote:
> Hey, Craig.  I haven't seen you around in years.
>
> For those who don't know, Craig is the author of Practical Raytracing in C:
>  "https://www.amazon.ca/Practical-Ray-Tracing-Craig-Lindley/dp/0471573019"
>
> (unless I have the wrong Craig Lindley  :-)  )
>
> David Buck

Wow, synchronicity - I've had that book for decades and it's down in my studio
right now. I was reading through it (and some Graphics Gems) just last weekend!


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Attachments:
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Preview of image 'practicalraytracinginc.jpg'
practicalraytracinginc.jpg


 

From: Craig Lindley
Subject: Re: Help With Image
Date: 30 Mar 2022 11:00:00
Message: <web.62446ff02a8c6bc62f73d2b2bc520638@news.povray.org>
David Buck <dav### [at] simberoncom> wrote:
> Hey, Craig.  I haven't seen you around in years.
>
> For those who don't know, Craig is the author of Practical Raytracing in C:
>  "https://www.amazon.ca/Practical-Ray-Tracing-Craig-Lindley/dp/0471573019"
>
> (unless I have the wrong Craig Lindley  :-)  )
>
> David Buck
>
>
> On 2022-03-29 2:54 p.m., Craig Lindley wrote:
> > Hello,
> >
> > I came across the attached image the other day that I thought was beautiful so I
> > decided to look at raytracing again. I hadn't done any raytracing since about
> > 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> > of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> > in the 1990's and today on my Mac it took about 10 minutes.
> >
> > Anyway. I would like to understand how this image was produced because I would
> > like to do something like it for this years Christmas card.
> >
> > It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> > POVRAY documentation for these types of spirals but I cannot seem to duplicate
> > the image accurately. I would guess that each color is its own Fibonacci spiral
> > but how they are positioned so they don't interfere with each other escapes me.
> >
> > Any help or suggestions would be appreciated. If anyone has access to the actual
> > POV file for this image I would love to have it.
> >
> > Thanks in advance.

Guilty as charged. Yes that is my book but like I said I haven't done any
raytracing in a long time. Thanks everyone for the hints on how to make this
image. Hopefully I'll get my raytracing chops back in trying to figure this
image out.


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From: Alain Martel
Subject: Re: Help With Image
Date: 30 Mar 2022 11:25:48
Message: <6244767c$1@news.povray.org>
Le 2022-03-29 à 14:54, Craig Lindley a écrit :
> Hello,
> 
> I came across the attached image the other day that I thought was beautiful so I
> decided to look at raytracing again. I hadn't done any raytracing since about
> 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> in the 1990's and today on my Mac it took about 10 minutes.
> 
> Anyway. I would like to understand how this image was produced because I would
> like to do something like it for this years Christmas card.
> 
> It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> POVRAY documentation for these types of spirals but I cannot seem to duplicate
> the image accurately. I would guess that each color is its own Fibonacci spiral
> but how they are positioned so they don't interfere with each other escapes me.
> 
> Any help or suggestions would be appreciated. If anyone has access to the actual
> POV file for this image I would love to have it.
> 
> Thanks in advance.

My proposition :
Start by constructing a single spiral and make it an object with an 
union. Don't give it any pigment nor finish yet.
Next, place several copies of that object, each rotated  so that it's 
constituent spheres are tangent to those of the previous.
In this case, there are height spirals, so, 45° of rotation between each.
In that step, give each spiral it's own pigment and finish.
In the finish, make them reflective with the metallic attribute.


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From: Craig Lindley
Subject: Re: Help With Image
Date: 31 Mar 2022 11:10:00
Message: <web.6245c3bb2a8c6bc62f73d2b2bc520638@news.povray.org>
David Buck <dav### [at] simberoncom> wrote:
> Hey, Craig.  I haven't seen you around in years.
>
> For those who don't know, Craig is the author of Practical Raytracing in C:
>  "https://www.amazon.ca/Practical-Ray-Tracing-Craig-Lindley/dp/0471573019"
>
> (unless I have the wrong Craig Lindley  :-)  )
>
> David Buck
>
>
> On 2022-03-29 2:54 p.m., Craig Lindley wrote:
> > Hello,
> >
> > I came across the attached image the other day that I thought was beautiful so I
> > decided to look at raytracing again. I hadn't done any raytracing since about
> > 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> > of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> > in the 1990's and today on my Mac it took about 10 minutes.
> >
> > Anyway. I would like to understand how this image was produced because I would
> > like to do something like it for this years Christmas card.
> >
> > It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> > POVRAY documentation for these types of spirals but I cannot seem to duplicate
> > the image accurately. I would guess that each color is its own Fibonacci spiral
> > but how they are positioned so they don't interfere with each other escapes me.
> >
> > Any help or suggestions would be appreciated. If anyone has access to the actual
> > POV file for this image I would love to have it.
> >
> > Thanks in advance.

David,

On a personal note, I think we met once a long time ago. If I recall correctly,
you worked for DEC in Colorado Springs. Are you still in the Springs? I live in
Rockrimmon.


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From: Craig Lindley
Subject: Re: Help With Image
Date: 31 Mar 2022 11:15:00
Message: <web.6245c4822a8c6bc62f73d2b2bc520638@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:

> > Hello,
> >
> > I came across the attached image the other day that I thought was beautiful so I
> > decided to look at raytracing again. I hadn't done any raytracing since about
> > 1993 so the POVRAY program has changed quite a bit. I am using the 3.8 version
> > of POVRAY and it is amazing. I retraced one of my old images that took 33 hours
> > in the 1990's and today on my Mac it took about 10 minutes.
> >
> > Anyway. I would like to understand how this image was produced because I would
> > like to do something like it for this years Christmas card.
> >
> > It seems to be made up of Fibonacci spirals but I am not sure. I looked at the
> > POVRAY documentation for these types of spirals but I cannot seem to duplicate
> > the image accurately. I would guess that each color is its own Fibonacci spiral
> > but how they are positioned so they don't interfere with each other escapes me.
> >
> > Any help or suggestions would be appreciated. If anyone has access to the actual
> > POV file for this image I would love to have it.
> >
> > Thanks in advance.
>
> My proposition :
> Start by constructing a single spiral and make it an object with an
> union. Don't give it any pigment nor finish yet.
> Next, place several copies of that object, each rotated  so that it's
> constituent spheres are tangent to those of the previous.

> In that step, give each spiral it's own pigment and finish.
> In the finish, make them reflective with the metallic attribute.

Yes this is what I will attempt next. I looked into the Doyle spirals as was
mentioned above but the math is challenging to say the least.


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From: David Buck
Subject: Re: Help With Image
Date: 31 Mar 2022 17:28:33
Message: <62461d01$1@news.povray.org>
I've lived in Ottawa since 1977 but I did work on contract in Colorado 
Springs around 1994 - 1995.  That's likely when we met.

David

On 2022-03-31 11:07 a.m., Craig Lindley wrote:
> 
> David,
> 
> On a personal note, I think we met once a long time ago. If I recall correctly,
> you worked for DEC in Colorado Springs. Are you still in the Springs? I live in
> Rockrimmon.
> 
>


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