POV-Ray : Newsgroups : povray.binaries.images : Prism. Server Time
12 Aug 2024 07:20:35 EDT (-0400)
  Prism. (Message 1 to 9 of 9)  
From: Tim Cook
Subject: Prism.
Date: 27 Oct 2003 22:37:57
Message: <3f9de495@news.povray.org>
Point light in sphere with hole cut in it for light
source; a spotlight does odd things (small image)...
the area of the spotlight is visible through the
transparent surface...not sure why that is...

-- 
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean

-----BEGIN GEEK CODE BLOCK-----
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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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Attachments:
Download 'prism_spotlight.jpg' (7 KB) Download 'prism.jpg' (24 KB)

Preview of image 'prism_spotlight.jpg'
prism_spotlight.jpg

Preview of image 'prism.jpg'
prism.jpg


 

From: JC (Exether)
Subject: Re: Prism.
Date: 28 Oct 2003 11:06:30
Message: <3f9e9406$1@news.povray.org>
I remember someone (I think it was Gilles but I'm not sure) reporting 
that parallel lights where not working properly with media and 
reflections. It might be the same with spot lights.
It seems that you're a fan of pink floyd aren't you ?  :-)

JC

Tim Cook wrote:
> Point light in sphere with hole cut in it for light
> source; a spotlight does odd things (small image)...
> the area of the spotlight is visible through the
> transparent surface...not sure why that is...
> 
> 
> ------------------------------------------------------------------------
> 
> 
> ------------------------------------------------------------------------
>


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From: Hughes, B 
Subject: Re: Prism.
Date: 28 Oct 2003 12:25:26
Message: <3f9ea686@news.povray.org>
"JC (Exether)" <no### [at] spamfr> wrote in message
news:3f9e9406$1@news.povray.org...
> I remember someone (I think it was Gilles but I'm not sure) reporting
> that parallel lights where not working properly with media and
> reflections. It might be the same with spot lights.
> It seems that you're a fan of pink floyd aren't you ?  :-)


Well, I know I sure am!

I checked with a scene of the same kind here and only saw the artifact
during one of the test renderings. It could just be a photon spacing or
count issue, or media samples. However, as you can see from this attached
image the rather mundane settings I ended up with seem to do okay.

There are two light sources, the spotlight (radius 3 falloff 4) and a dim
distant room light. The dispersion is at 1.2 with default samples. The media
is scattering type 1 with a 0.1 color value and extinction of 0 (used only
for box containing only the prism and spotlight) and no other parameters.
Refraction ior 1.5. Photons spacing 0.03 having media 50,1.

Do you have a media for both room and prism? That could be a media samples
and even an intervals issue.
-- 
Bob H.
http://www.3digitaleyes.com


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-_.jpg


 

From: Tim Cook
Subject: Re: Prism.
Date: 28 Oct 2003 12:47:29
Message: <3f9eabb1$1@news.povray.org>
I have two separate prisms; the one that's doing the refracting
has no_image 'cuz it takes forever to render otherwise, the
one that's visible is a cheapo materialed copy in front of that
to be a visible prism.


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From: Hughes, B 
Subject: Re: Prism.
Date: 28 Oct 2003 12:54:35
Message: <3f9ead5b@news.povray.org>
"Tim Cook" <z99### [at] bellsouthnet> wrote in message
news:3f9eabb1$1@news.povray.org...
> I have two separate prisms; the one that's doing the refracting
> has no_image 'cuz it takes forever to render otherwise, the
> one that's visible is a cheapo materialed copy in front of that
> to be a visible prism.

Hmmm, interesting. Well, could it be the global settings max_trace_level
needing to be higher than the default of 5 surfaces?


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From: Hughes, B 
Subject: Re: Prism. A photons artifact?
Date: 28 Oct 2003 17:04:23
Message: <3f9ee7e7@news.povray.org>
"Hughes, B." <omn### [at] charternet> wrote in message
news:3f9ead5b@news.povray.org...
> "Tim Cook" <z99### [at] bellsouthnet> wrote in message
> news:3f9eabb1$1@news.povray.org...
> > I have two separate prisms; the one that's doing the refracting
> > has no_image 'cuz it takes forever to render otherwise, the
> > one that's visible is a cheapo materialed copy in front of that
> > to be a visible prism.
>
> Hmmm, interesting. Well, could it be the global settings max_trace_level
> needing to be higher than the default of 5 surfaces?

I should have also said global settings *photons* block max_trace_level too,
I guess, but I'm thinking it has nothing to do with the problem.

Anyway, reason I'm back replying to myself here is that I thought I had
stumbled upon the reason I was either seeing or not seeing the same artifact
you had gotten. Then it turned out *not* to be the answer, which was using
photon blocks in the lights, versus not using them and letting defaults
work.

Fact is, I see the same artifact now after having made several changes in
the camera, lights, prism shape, etc. I'll certainly let you know if I find
out the exact reason for this happening, but it's slow going to test render
at a good size. And besides it's confounding me, making matters worse. That
other image I had shown before wasn't antialiased or retouched in any way,
just so you know.  :-)

Bob H.


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From: Marc Champagne
Subject: Re: Prism. - 2 attachments
Date: 28 Oct 2003 22:15:05
Message: <Xns9422E1D3C73A5POVMIKA@204.213.191.226>
Tim Cook <z99### [at] bellsouthnet> wrote in
news:3f9de495@news.povray.org: 

> Point light in sphere with hole cut in it for light
> source; a spotlight does odd things (small image)...
> the area of the spotlight is visible through the
> transparent surface...not sure why that is...
> 

I did one too, but I didn't use media.



-- 
Marc Champagne
marcch.AT.videoSPAMNOTtron.DOT.ca.invalid
Montrea l, Canada


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Attachments:
Download 'Photon.Party2.jpg' (24 KB) Download 'Photon.Party1.jpg' (12 KB)

Preview of image 'Photon.Party2.jpg'
Photon.Party2.jpg

Preview of image 'Photon.Party1.jpg'
Photon.Party1.jpg


 

From: Hughes, B 
Subject: Re: Prism. - 2 attachments
Date: 29 Oct 2003 00:10:32
Message: <3f9f4bc8@news.povray.org>
"Marc Champagne" <marcch.AT.videoSPAMNOTtron.DOT.ca.invalid> wrote in
message news:Xns### [at] 204213191226...
>
> I did one too, but I didn't use media.

Could've fooled me. And the more I look at it, I can't imagine that is only
light shining on a background surface or something.

Back to the artifact problem... I sure had narrowed the thing down enough to
convince myself it was due to reflection, having forgotten I used that only
after I posted my image showing it didn't have the spotlight lines crossing
through the prism. Now that doesn't seem the answer either.

I finally got my test scene back to the original one, close enough that the
artifact disappeared, but it seemed to be because I used 'media 50,1' in the
global settings photons. And also without reflection. Yet, that was proving
to be the wrong assumption too. When I changed the spotlight radius to 2
instead of 1 it went away, so I figured it must be something about the very
small radius or at least both that and falloff being nearly as small.

Well, a lot of trial and error later, I'm still a bit mystified. It could be
mostly the spacing value changes I've used. At this point I couldn't be
sure. It's like theirs a sweet spot among all the parameters, which is about
as good an answer I can give about it. One thing is certain, and that'd be
to say variations really wreak havoc on the way the resulting media+photons
appears. In turn, this all means it probably isn't a program bug if one way
of rendering is okay. I suppose not, anyhow.

Bob H.


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From: Marc Champagne
Subject: Re: Prism. - 2 attachments
Date: 22 Nov 2003 22:40:54
Message: <Xns943BE670D684FPOVMIKA@204.213.191.226>
"Hughes, B." <omn### [at] charternet> wrote in
news:3f9f4bc8@news.povray.org: 

> "Marc Champagne"
> <marcch.AT.videoSPAMNOTtron.DOT.ca.invalid> wrote in 
> message news:Xns### [at] 204213191226... 
>>
>> I did one too, but I didn't use media.
> 
> Could've fooled me. And the more I look at it, I can't
> imagine that is only light shining on a background surface
> or something. 

[snip]

I'm content with my attempt of the prism, I guess it attracts
many to try and it always somewhat resembles Pink Floyd's
album. 

The code is in ptsf, subject MIKA pink floyd Album Cover
Code. 

ciao


-- 
Marc Champagne
marcch.AT.videoSPAMNOTtron.DOT.ca.invalid
Montreal, Canada


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