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From: Maurice
Subject: Re: Glass thingy
Date: 9 Jan 2005 14:58:44
Message: <41e18cf4$1@news.povray.org>
George Pantazopoulos wrote:
>>Well, not very proud of the current result really.
>>I rendered the scene with the HDR image off and a cylinderical
>>lightsource over the blob. Saving the photon and radiosity data.
>>
> 
> 
> Pardon my ignorance, but I don't see a need for radiosity in your image. Why
> is it there? I would try disabling radiosity for now and tweak your photons
> settings. This would simplify your life by eliminate a big variable from
> the equation :)

Radiosity is used to cause caustics?

>>The caustics are now transfomred to shadows... I'm now renderingwith a
>>less reflective floor (0.1). But I'm afraid I'll loose the effect I was
>>going for.
>>
> 
> 
> What exact effect are you looking for, and what is the diffuse component of
> your floor?

Okay. It is rather difficult to explain, so I set up a page on my 
website to show what is going on and what I'm after. Please visit:

http://members.home.nl/m.e.j.r.hendrix/POV/glass.html

-- 
Maurice


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From: Ger
Subject: Re: Glass thingy
Date: 9 Jan 2005 16:20:46
Message: <41e1a02a@news.povray.org>
On Sunday 09 January 2005 20:58, Maurice wrote :

> 
> Okay. It is rather difficult to explain, so I set up a page on my
> website to show what is going on and what I'm after. Please visit:
> 
> http://members.home.nl/m.e.j.r.hendrix/POV/glass.html
> 

Looking for something like in the attached picture?

-- 
Ger


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Preview of image 'asbak-011-600.jpg'
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From: Maurice
Subject: Re: Glass thingy
Date: 9 Jan 2005 16:22:50
Message: <41e1a0aa$1@news.povray.org>
Ger wrote:
> On Sunday 09 January 2005 20:58, Maurice wrote :
> 
> 
>>Okay. It is rather difficult to explain, so I set up a page on my
>>website to show what is going on and what I'm after. Please visit:
>>
>>http://members.home.nl/m.e.j.r.hendrix/POV/glass.html
>>
> 
> 
> Looking for something like in the attached picture?
> 
> 
> 
> ------------------------------------------------------------------------
> 
Yes. Although that might be overdoing it a bit ;-)


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From: Ger
Subject: Re: Glass thingy
Date: 9 Jan 2005 16:33:04
Message: <41e1a30f@news.povray.org>
On Sunday 09 January 2005 22:22, Maurice wrote :

> Ger wrote:
>> On Sunday 09 January 2005 20:58, Maurice wrote :
>> 
>> 
>>>Okay. It is rather difficult to explain, so I set up a page on my
>>>website to show what is going on and what I'm after. Please visit:
>>>
>>>http://members.home.nl/m.e.j.r.hendrix/POV/glass.html
>>>
>> 
>> 
>> Looking for something like in the attached picture?
>> 
>> 
>> 
>> ------------------------------------------------------------------------
>> 
> Yes. Although that might be overdoing it a bit ;-)

This is what I used


//...............................................
global_settings {
        max_trace_level 255
        photons {
                count 1000000
                autostop 0
                jitter .1
                }
        }

// light source just inside the ashtray
light_source{ 0 color rgb <1,1,1>*4 translate <-160,0.51,40>
        photons {
                refraction on
                reflection on
        }}

#declare YourBlobbyGlassThing =
        blob.................. etc
        
        material { M_Glass3 }
        photons {
                target
                refraction on
                reflection on
                collect on
                }

        }
        
object { YourBlobbyGlassThing }

With the ashtray this used ~1Gb memory and 70~80 hours to render at 1200 x
600 pixels, so you might want to lower the count first :)

-- 
Ger


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From: Maurice
Subject: Re: Glass thingy
Date: 10 Jan 2005 12:17:37
Message: <41e2b8b1$1@news.povray.org>
Ger wrote:

Thanks for your input, it is very inspiring. See comments below.
> //...............................................
> global_settings {
>         max_trace_level 255
>         photons {
>                 count 1000000
>                 autostop 0
>                 jitter .1
>                 }
>         }
> 
That is a very high count. I'm using default value. I start to 
understand why I don't get caustics
My photons settings:
   photons {
   	spacing 1/2
	gather 20,100
   	max_trace_level 300
   	jitter 0.4
   	adc_bailout 0.01
   	save_file "newt.photons"
   }

And radiosity block:
   radiosity {
     samples 1
     pretrace_start 0.08
     pretrace_end   0.01
     count 800
     nearest_count 8
     error_bound 0.07
     recursion_limit 2
     low_error_factor .5
     gray_threshold 0.0
     minimum_reuse 0.015
     brightness 1 //0.7
     adc_bailout 0.01/2
     normal on
     randomize on
     //media on
     max_sample 1.0
     load_file "newt.radiosity"
     always_sample no
   }

> // light source just inside the ashtray
> light_source{ 0 color rgb <1,1,1>*4 translate <-160,0.51,40>
>         photons {
>                 refraction on
>                 reflection on
>         }}

Mmm that's interesting. My lightsource has no photons attached :-\

> #declare YourBlobbyGlassThing =
>         blob.................. etc
>         
>         material { M_Glass3 }
>         photons {
>                 target
>                 refraction on
>                 reflection on
>                 collect on
>                 }
> 
>         }
>         

photons block of the blob:
   photons{
     target 0.05
     refraction on
     reflection on
     collect off // **
   }

Why did you switch on collect? Doesn't that mean that photons are not 
exiting the object after they hit it?
> object { YourBlobbyGlassThing }

> With the ashtray this used ~1Gb memory and 70~80 hours to render at 1200 x
> 600 pixels, so you might want to lower the count first :)

I'm hoping that won't be the time for my render... Did you render with 
saved photons or calculate the photons dyuring the actual render.

My idea is now to do as follows:
1. Render @ 80x40 with photons, radiosity and lightsource on; save_file 
for photons and radiosity
2. Render @ 800x400 with lightsource off and HDR image on, load_file for 
photons and radiosity.

I think I'll also try out what happens if I switch on/off radiosity as 
George Patazopoulos suggested the scene does not need it. I'm not 
convinced but the render results will show.

Bedankt for your help,
-- 
Maurice


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From: Ger
Subject: Re: Glass thingy
Date: 10 Jan 2005 16:40:12
Message: <41e2f63b@news.povray.org>
On Monday 10 January 2005 18:17, Maurice wrote :

> That is a very high count. I'm using default value. I start to
> understand why I don't get caustics

You might want to start way lower to get a basic idea of what is the outcome
is gonna be

> My photons settings:
>    photons {
>    spacing 1/2
> gather 20,100
>    max_trace_level 300
>    jitter 0.4
>    adc_bailout 0.01
>    save_file "newt.photons"
>    }
> 
> And radiosity block:
>    radiosity {
>    }

I didn't have radiosity because it tends to wash out a lot of sharp effects

> Mmm that's interesting. My lightsource has no photons attached :-\
> 

As far as I know (but don't hit me over the head if I'm wrong) you need that
to get any caustics effects.

> 
> photons block of the blob:
>    photons{
>      target 0.05
>      refraction on
>      reflection on
>      collect off // **
>    }
> 
> Why did you switch on collect? Doesn't that mean that photons are not
> exiting the object after they hit it?

Hmm, don't remember now.

> 
> I'm hoping that won't be the time for my render... Did you render with
> saved photons or calculate the photons dyuring the actual render.
> 

All in 1 go, so no in between saves.

> My idea is now to do as follows:
> 1. Render @ 80x40 with photons, radiosity and lightsource on; save_file
> for photons and radiosity
> 2. Render @ 800x400 with lightsource off and HDR image on, load_file for
> photons and radiosity.
> 
> I think I'll also try out what happens if I switch on/off radiosity as
> George Patazopoulos suggested the scene does not need it. I'm not
> convinced but the render results will show.
> 
I sure would switch it off to make the caustics effect more clear

> Bedankt for your help,

Graag gedaan :)
-- 
Ger


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From: Alain
Subject: Re: Glass thingy
Date: 10 Jan 2005 22:50:15
Message: <41e34cf7$1@news.povray.org>
Maurice nous apporta ses lumieres en ce 2005-01-10 12:17:
> Ger wrote:
> 
> Thanks for your input, it is very inspiring. See comments below.
> 
>> //...............................................
>> global_settings {
>>         max_trace_level 255
>>         photons {
>>                 count 1000000
>>                 autostop 0
>>                 jitter .1
>>                 }
>>         }
>>
> That is a very high count. I'm using default value. I start to 
> understand why I don't get caustics
That's NOT a very high count. Look at all the dots...
Using spacing, I can easily get over 10 000 000
> My photons settings:
>   photons {
>       spacing 1/2
>     gather 20,100
>       max_trace_level 300// I think that it can't go over 255
>       jitter 0.4
>       adc_bailout 0.01
>       save_file "newt.photons"
>   }
You usualy need smaler spacing. That's about 1 photon per half unit... I 
rarely start with a spacing over 1/10


> 
> Mmm that's interesting. My lightsource has no photons attached :-\
A light_source without a photons block don't shoot any, and don't 
contribute to the photons caustics.
> 
>> #declare YourBlobbyGlassThing =
>>         blob.................. etc
>>                 material { M_Glass3 }
>>         photons {
>>                 target
>>                 refraction on
>>                 reflection on
>>                 collect on
>>                 }
>>
>>         }
>>         
> 
> 
> photons block of the blob:
>   photons{
>     target 0.05
>     refraction on
>     reflection on
>     collect off // **
>   }
> 
> Why did you switch on collect? Doesn't that mean that photons are not 
> exiting the object after they hit it?
Collect on make the object show photons effects ON it. It don't stop the 
photons. As, normaly, photons don't show on mostly reflective and/or 
transparent object, collect on just waiste time for usualy negligeagle 
effect.


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From: Maurice
Subject: Re: Glass thingy
Date: 12 Jan 2005 13:54:33
Message: <41e57269$1@news.povray.org>
Ger wrote:

> Looking for something like in the attached picture?

Ger,
Did you use differently coloured lightsources to get those rainbow-like 
effects in the top of the picture?

-- 
Maurice


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From: Ger
Subject: Re: Glass thingy
Date: 12 Jan 2005 15:13:42
Message: <41e584f6@news.povray.org>
On Wednesday 12 January 2005 19:54, Maurice wrote :

> Ger wrote:
> 
>> Looking for something like in the attached picture?
> 
> Ger,
> Did you use differently coloured lightsources to get those rainbow-like
> effects in the top of the picture?
> 
Nope, just the one light that I gave you in the code bit.
The whole scene is just 3 things, the plane, the ashtray and 1 light

-- 
Ger


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From: Alain
Subject: Re: Glass thingy
Date: 12 Jan 2005 19:14:12
Message: <41e5bd54$1@news.povray.org>
Maurice nous apporta ses lumieres en ce 2005-01-12 13:54:
> Ger wrote:
> 
>> Looking for something like in the attached picture?
> 
> 
> Ger,
> Did you use differently coloured lightsources to get those rainbow-like 
> effects in the top of the picture?
> 
Try adding dispersion <some value> in your interior block. Realistic values from 1.001
to 1.03, 
artistic values from 0.7 to 0.99 (reverced effect) and 1.05 to 1.5 (stronger to WAY
stronger 
than real effect)
Zero and negative value make the object reflective with no transparency left.

Alain


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