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From: Stefan Viljoen
Subject: Re: Caustics on a surface under an object - Tim Niklas
Date: 23 May 2004 14:47:06
Message: <40b0f1a8@news.povray.org>
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Tim Nikias v2.0 wrote:
>> If I want caustics on a surface BELOW a photon target, must the surface
> that
>> the photon target is on also be a photon target?
>>
>> I have tried many combinations but simply cannot get caustics on a
>> surface "behind" a photon target, even with very small spacings and lots
>> of
> photons
>> - all my photon caustics stay confined to the glass object. I simply
> cannot
>> get caustics onto the table "behind" the glass standing on it.
>
> Can you provide small, minimal sample scene (post it on
> povray.binaries.scene-files), so that I could have a look at it? You could
> also try to put both objects in a union and shoot photons at the union,
> but that's just a random guess, nothing based on experience or such.
>
Hi Tim!
Thanks for replying to my post - I think I have at least demystified it for
myself a bit. I made the following test scene:
global_settings
{
adc_bailout 0.05
max_trace_level 10
photons
{
spacing 0.01
jitter 0.15
max_trace_level 10
adc_bailout 0.05
autostop 0
radius ,1.75
//save_file "phottest.pht"
}
}
camera
{
location <0,0,5>
look_at <0,2,0>
}
light_source
{
<4,4,5>
color rgb <1,1,1>*2
photons
{
refraction on
reflection on
}
}
box
{
<-1,-1,-1>
<1,1,1>
material
{
texture
{
pigment
{
color rgb <1,0,0>
}
}
}
scale <2,2,1>
}
cylinder
{
<-1,-1,-1>,
<-1,1,2>
0.25
material
{
texture
{
pigment
{
color rgbft <0,0,1,0.3,0.65>
}
finish
{
diffuse 0.55
ambient 0.45
specular 0.9
roughness 0.2
metallic 0.25
reflection 0.25
}
}
interior
{
ior 1.3
dispersion 1.4
dispersion_samples 10
caustics 2
}
}
translate <1,0,0>
photons
{
target 0.75
reflection on
refraction on
}
}
This works ok. However in my scene I am working on (a bit too big to post),
specifying the object like this (I copied exactly the same ior, texture,
and shape) makes it turn absolutely 255,255,255 white - I have one very
distant (1000 units away) light. Specifying "collect off" in the glass
object's statement makes its texture be okay, but I guess THIS is why it
does not leave caustics on the surface it is standing on.
Any idea how I can prevent the photon object being "white out"-ed when I
remove "collect off"? Obviously I am making some mistake and specifying
"collect off" makes the class NOT leave caustics like I want it to.
Thanks!
--
Stefan Viljoen
Software Support Technician
Polar Design Solutions
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From: Alain
Subject: Re: Caustics on a surface under an object - Tim Niklas
Date: 23 May 2004 18:22:02
Message: <40b1240a@news.povray.org>
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
<title></title>
</head>
<body vlink="#551a8b" alink="#ee0000" link="#0000ee" text="#330000"
bgcolor="#ffffcc">
Stefan Viljoen <rylan@ nous apporta ses lumieres ainsi en ce
2004/05/23 14:45... : <br>
<blockquote cite="mid40b0f1a8@news.povray.org" type="cite">
<pre wrap="">
Thanks for replying to my post - I think I have at least demystified it for
myself a bit. I made the following test scene:
global_settings
{
adc_bailout 0.05
//max_trace_level 10 commented out
photons
{
spacing 0.01
jitter 0.15
max_trace_level 10
adc_bailout 0.05
autostop 0
radius ,1.75
//save_file "phottest.pht"
}
}
camera
{
location <0,0,5>
look_at <0,2,0>// -> <0,0,0>
}
light_source
{
<4,4,5>
color rgb <1,1,1>*2
photons
{
refraction on
reflection on
}
}
box
{
<-1,-1,-1>
<1,1,1>
material
{
texture
{
pigment
{
color rgb <1,0,0>// -> rgb 1
}
}
}
scale <2,2,1>
}
cylinder
{
<-1,-1,-1>,
<-1,1,2>
0.25
material
{
texture
{
pigment
{
color rgbft <0,0,1,0.3,0.65>// -> rgbft
<0.9,0.9,1,0.99,0.0>
}
finish
{
diffuse 0.55//-> 0.1
ambient 0.45// -> 0.0
specular 0.9
roughness 0.2
metallic 0.25
reflection 0.25
}
}
interior
{
ior 1.3
dispersion 1.4
dispersion_samples 10// -> 20
//caustics 2// you don't need faked caustics
}
}
translate <1,0,0>
photons
{
target 0.75
reflection on
refraction on collect off
}
}
This works ok. However in my scene I am working on (a bit too big to post),
specifying the object like this (I copied exactly the same ior, texture,
and shape) makes it turn absolutely 255,255,255 white - I have one very
distant (1000 units away) light. Specifying "collect off" in the glass
object's statement makes its texture be okay, but I guess THIS is why it
does not leave caustics on the surface it is standing on.
Any idea how I can prevent the photon object being "white out"-ed when I
remove "collect off"? Obviously I am making some mistake and specifying
"collect off" makes the class NOT leave caustics like I want it to.
Thanks!
</pre>
</blockquote>
Changing the table to white and the "glass" to almost clear does show
both reflection and refraction caustics with strong dispersion.<br>
My changes to the glass are: remove caustics 2, add collect off in th
photons block, recolor to bluish white "rgbft
<0.9,0.9,1,0.99,0.0>" instead of blue, change the ambient to 0
and diffuse to 0.1, increased dispersion_samples to 20.<br>
I also made the "table" white.<br>
Reverted to default Max_trace_level hithout any obvious black spot.<br>
It renders somewhat faster to.<br>
<img height="768" width="1024" alt=""
src="cid:par### [at] qwerty gov"><br>
<br>
Alain<br>
</body>
</html>
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Attachments:
Download 'test.png' (217 KB)
Preview of image 'test.png'
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From: Alain
Subject: Re: Caustics on a surface under an object - Tim Niklas
Date: 23 May 2004 18:37:55
Message: <40b127c3@news.povray.org>
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
<title></title>
</head>
<body>
I missed that one: to bright light_source washing things out<br>
Removing the *2 give much beter results.<br>
<blockquote cite="mid40b1240a@news.povray.org" type="cite">
<blockquote cite="mid40b0f1a8@news.povray.org" type="cite">
<pre wrap="">
light_source
{
<4,4,5>
>>>>>>>> color rgb <1,1,1>*2
<<<<<<<<<< change to rgb 1
photons
{
refraction on
reflection on
}
}
</pre>
</blockquote>
<img height="384" width="512" alt=""
src="cid:par### [at] qwertygov"><br>
</blockquote>
Alain<br>
</body>
</html>
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Attachments:
Download 'test.png' (56 KB)
Preview of image 'test.png'
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From: Florian Brucker
Subject: Re: Caustics on a surface under an object - Tim Niklas
Date: 24 May 2004 06:24:29
Message: <40b1cd5d$1@news.povray.org>
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Alain wrote:
> Content-Type: text/html; charset=us-ascii
Please do not post HTML-posts in these groups. Thanks :)
Florian
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From: Alain
Subject: Re: Caustics on a surface under an object - Tim Niklas
Date: 24 May 2004 19:00:22
Message: <40b27e86$1@news.povray.org>
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Florian Brucker nous apporta ses lumieres ainsi en ce 2004/05/24 06:29... :
> Alain wrote:
> > Content-Type: text/html; charset=us-ascii
>
> Please do not post HTML-posts in these groups. Thanks :)
>
>
> Florian
I don't have the choice, if I include any image, it's going to be HTML.
I'm not the only one who use HTML posting, it's just that I don't use
"default" white background that make it show.
Alain
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