"Cousin Ricky" <ric### [at] yahoocom> wrote:

> Have you tried dispersion? (Since that is what a rainbow is.)

tried:
  interior { ior 1.33 caustics 1 dispersion 1.01 dispersion_samples 9 }
  interior { ior 1.33 caustics 1 dispersion 1.1 dispersion_samples 100 }
  (just more render time)

still nothing

obviously this is where knowing what you're doing comes in handy.


something about the layer, I havent a clue.

I dont really care, but for the group at least. Something they might use one
day.

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If your'e interested in this and want answers, they might be found here.
Only had the time to grab and render:
galilean_view_eyepiece.pov

http://www.arachnoid.com/raytracing/telescope1.html

Sweet info page from what I've seen so far, I'll need to spend more time on it

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Attachments:
Download 'galilean_view_eyepiece.png' (28 KB)

Preview of image 'galilean_view_eyepiece.png'

alphaQuad nous illumina en ce 2008-05-19 19:28 -->
> "Cousin Ricky" <ric### [at] yahoocom> wrote:
> 
>> Have you tried dispersion? (Since that is what a rainbow is.)
> 
> tried:
>   interior { ior 1.33 caustics 1 dispersion 1.01 dispersion_samples 9 }
>   interior { ior 1.33 caustics 1 dispersion 1.1 dispersion_samples 100 }
>   (just more render time)
> 
> still nothing
> 
> obviously this is where knowing what you're doing comes in handy.
> 
> 
> something about the layer, I havent a clue.
> 
> I dont really care, but for the group at least. Something they might use one
> day.
> 
> 
> 
You don't need to use caustics here.

-- 
Alain
-------------------------------------------------
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to 
tell from 10,000 feet."           -- Anon.

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"alphaQuad" <alp### [at] earthlinknet> wrote:
> I'd bet money it can be done, tho I cannot make it at this time.
>
> http://news.povray.org/*/attachment/%3C48202ea0%40news.povray.org%3E/glory.jpg
> Glory is your shadow encircled in a rainbow.

Here's a proof-of-concept:

#ifndef (Disp) #declare Disp = 0; #end
#ifndef (Reps) #declare Reps = 20; #end
#declare Spacing = <sqrt(3), 0, 1>;

global_settings { assumed_gamma 1 max_trace_level 60 }

camera
{  location Reps * Spacing.x * 2 * y
   look_at 0
   angle 30
   right image_width * x
   up image_height * y
}

light_source { Reps * 1000 *y, rgb 1 }

sky_sphere
{  pigment { gradient y color_map { [0 rgb 0.85][1 rgb 0.50] } }
}

plane { y, -1 pigment { rgb 1 } }

#declare t_Drop = texture
{  pigment { rgbt 1 }
   finish
   {  reflection { 0 1 fresnel } conserve_energy
      specular 1 roughness 0.001
   }
}
#declare i_Drop = interior
{  ior 1.333
   #if (Disp) dispersion 1 + Disp * 0.007 dispersion_samples 10 #end
}
#declare m_Drop = material { texture { t_Drop } interior { i_Drop } }

#declare Half_sheet = union
{  #declare I = 0;
   #while (I < Reps)
      #declare J = 0;
      #while (J < Reps)
         sphere { <J, 0, I> * Spacing, 0.4999 }
         #declare J = J + 1;
      #end
      #declare I = I + 1;
   #end
   translate (1 - Reps) / 2 * Spacing
}

#declare Sheet = union
{  object { Half_sheet translate Spacing/4 }
   object { Half_sheet translate -Spacing/4 }
}

object
{  Sheet
   material { m_Drop }
}

This first image has no dispersion, and was run with declare=Reps=3 on the
command line.

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Attachments:
Download 'glory-poc-ed.jpg' (6 KB)

Preview of image 'glory-poc-ed.jpg'

"Cousin Ricky" <ric### [at] yahoocom> wrote:
> "alphaQuad" <alp### [at] earthlinknet> wrote:
> > I'd bet money it can be done, tho I cannot make it at this time.
> >
> > http://news.povray.org/*/attachment/%3C48202ea0%40news.povray.org%3E/glory.jpg
> > Glory is your shadow encircled in a rainbow.
>
> Here's a proof-of-concept:

This second image has 10 times the dispersion of water (according to some number
i once saw somewhere in the POV-Ray material).  It was run with declare=Reps=3
declare=Disp=10 on the command line.

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Attachments:
Download 'glory-poc-10.jpg' (13 KB)

Preview of image 'glory-poc-10.jpg'

Glider was a scripted output, a script written before I understood much about
pov that has become clear.

output was:
union {
mesh {


today I'd change union to object, (or put matrix inside mesh and declare the
mesh) being that there is no union of triangles which are inside mesh{}. It
could be said the glider code is wrong (doh) even tho it works.


Before I am corrected, all apologies for producing ugly code. I'll do better in
the future.

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I am finding this whole thread pretty interesting and it is something which i
have looked into before. Having played around with these features and building
a setup which has the technicalities of a rainbow taken into account I created
the following image a while back.

Notably this is not quite what you are looking for, the light source comes
through the plane (by means of the blue hole) and the rainbow emerges due to
bending the light back (This may seem a strange idea however if you imagine
that the screen is the observer then by looking at the screen we see the light
that would be seen by the observer).

The set up is similar to what you are trying. This thread has prompted me to
play around with the set up and I have found that oddly enough the setup does
require that caustics be on, this doesnt make sense but appears to be the case.
I will be continuing to play around so will let everyone know what I find with
further investigation.

Malcolm

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Attachments:
Download 'caustic rainbow4.jpg' (155 KB)

Preview of image 'caustic rainbow4.jpg'

Many a discovery it seems can be made in one evening. I have been playing around
with the little rainbow creating setup i have here and have discovered many
interesting things.

Firstly I have overcome an initial curiosity that things only worked with
caustics on. Still not entirely sure what the quirk was here but whatever it
was it is sorted and caustics are as stated by everyone here unnecesary.

A second point of interest worth mentioning is that pov ray will not split a
single white light source by any method that I can find. However if one creates
a whole set of coloured light sources at the same point then this equates to
white on normal surfaces however povray wil differentially split this light to
produce a beautiful spectrum.

A third discovery is that a large dispersion is required otherwise one will
mainly see white as the colours are not being seperated enough.

A fourth note which I need to solve is that I am still not quite producing a
glory as the camera is pointing at a screen which is showing the spectrum. in
other words I cannot get the 'water' to show up the glory, I can only see the
image that it projects onto a screen.

Please enjoy the attached image and ask about anything of interest.

Malcolm

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Attachments:
Download 'caustic rainbow.jpg' (294 KB)

Preview of image 'caustic rainbow.jpg'

Did you remember to turn the photon settings on?

-- 
Tim Cook
http://empyrean.digitalartsuk.com

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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Tim Cook <z99### [at] gmailcom> wrote:
> Did you remember to turn the photon settings on?
>
> --
> Tim Cook
> http://empyrean.digitalartsuk.com
>
> -----BEGIN GEEK CODE BLOCK-----
> Version: 3.12
> GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
> N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
> PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
> D++(---) G(++) e*>++ h+ !r--- !y--
> ------END GEEK CODE BLOCK------


Yep photons are necessary to see anything aside from a reflection. Although it
is worth noting that the first image I posted had a lot more photons than the
second which is partly why the second is not so neat.

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