POV-Ray : Newsgroups : povray.binaries.images : Glass for v3.8 finish features Server Time
2 Dec 2022 11:41:22 EST (-0500)
  Glass for v3.8 finish features (Message 5 to 14 of 14)  
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From: Thomas de Groot
Subject: Re: Glass for v3.8 finish features
Date: 9 Aug 2022 08:53:02
Message: <62f258ae$1@news.povray.org>
Op 8-8-2022 om 20:06 schreef MichaelJF:
> 
> Very nice, indeed. Seems I should take a look into the general 
> discussion occasionally. IMO there is a small drawback. The "caustics" 
> at the table did not correspond to the light sources within the HDRI 
> image. But I'm nitpicking ...
> 

You are right as I added an additional light source and the hdri light 
sources have been overflooded. I needed it mainly as a backdrop to the 
scene.

initially, I wanted to concentrate on the hdr light sources though...

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Glass for v3.8 finish features
Date: 9 Aug 2022 10:50:09
Message: <62f27421$1@news.povray.org>
Op 9-8-2022 om 14:53 schreef Thomas de Groot:
> initially, I wanted to concentrate on the hdr light sources though...
> 
...and when I do, no photons are generated!

I use
   photons {
     refraction on
     reflection on
   }

for the sphere with the hdr map, identical to the code for the light 
source. Decreasing spacing down to a ridiculously small value doesn't 
change anything. I must be missing something here...

-- 
Thomas


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From: William F Pokorny
Subject: Re: Glass for v3.8 finish features
Date: 9 Aug 2022 11:16:11
Message: <62f27a3b$1@news.povray.org>
On 8/9/22 10:50, Thomas de Groot wrote:
> Op 9-8-2022 om 14:53 schreef Thomas de Groot:
>> initially, I wanted to concentrate on the hdr light sources though...
>>
> ...and when I do, no photons are generated!
> 
> I use
>    photons {
>      refraction on
>      reflection on
>    }
> 
> for the sphere with the hdr map, identical to the code for the light 
> source. Decreasing spacing down to a ridiculously small value doesn't 
> change anything. I must be missing something here...
> 

I'm perhaps not following, but...

Taking your hdr sphere to be an actual hollow sphere, you are making it 
a photon target for any photon light sources by adding the photon block 
above. In other words - as far as I know - there is no way to shoot 
photons from other than a traditional light sources.

Aside: I've never tried to shoot photons from a light source inside a 
hollow object at the inside surface of that object. I'm not sure it 
would work given the how the radial 'shooting pattern' is aimed at 
target objects. Perhaps this the reason why you get no photons? Hmm, 
maybe a spot light would work... Too long since I've played with photons.

Bill P.


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From: Chris R
Subject: Re: Glass for v3.8 finish features
Date: 9 Aug 2022 11:20:00
Message: <web.62f27ad2e64472364326bc25cc1b6e@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> I was happy to read the instructions for a version 3.8 glass material,
> provided by Alain Martel
>
>
https://news.povray.org/povray.general/thread/%3Cweb.62e942de1adc8eb48a3c0aee5cc1b6e%40news.povray.org%3E/
>
> and wanted to try them out myself. This is the result. The different
> variations include air bubbles and the albedo keyword in the cylinder, a
> scattering media inside the ovus, and appropriate fade_color and
> fade_distance for the different objects. The background is a hdr map,
> and a single additional point light are completing the setup.
>
> A big thanks to Alain! This is an excellent starting ground for quality
> glass material indeed.
>
> --
> Thomas
This is why I love working with POV and this community.  There's always someone
who has thought about the same problems and is willing to share their experience
(and code!)


-- Chris R.


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From: MichaelJF
Subject: Re: Glass for v3.8 finish features
Date: 9 Aug 2022 13:09:22
Message: <62f294c2$1@news.povray.org>
Am 09.08.2022 um 17:16 schrieb William F Pokorny:
> On 8/9/22 10:50, Thomas de Groot wrote:
>> Op 9-8-2022 om 14:53 schreef Thomas de Groot:
>>> initially, I wanted to concentrate on the hdr light sources though...
>>>
>> ...and when I do, no photons are generated!
>>
>> I use
>>    photons {
>>      refraction on
>>      reflection on
>>    }
>>
>> for the sphere with the hdr map, identical to the code for the light 
>> source. Decreasing spacing down to a ridiculously small value doesn't 
>> change anything. I must be missing something here...
>>
> 
> I'm perhaps not following, but...
> 
> Taking your hdr sphere to be an actual hollow sphere, you are making it 
> a photon target for any photon light sources by adding the photon block 
> above. In other words - as far as I know - there is no way to shoot 
> photons from other than a traditional light sources.
> 
> Aside: I've never tried to shoot photons from a light source inside a 
> hollow object at the inside surface of that object. I'm not sure it 
> would work given the how the radial 'shooting pattern' is aimed at 
> target objects. Perhaps this the reason why you get no photons? Hmm, 
> maybe a spot light would work... Too long since I've played with photons.
> 
> Bill P.
Unfortunatelly, Bill seems to be right. I tried a bit, but it seems to 
be impossible to persuade a HDRI light to cast photons, so we need POV 
4.0 ;)

Best regards,
Michael


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From: Thomas de Groot
Subject: Re: Glass for v3.8 finish features
Date: 10 Aug 2022 02:04:55
Message: <62f34a87$1@news.povray.org>
Op 09/08/2022 om 19:09 schreef MichaelJF:
> Am 09.08.2022 um 17:16 schrieb William F Pokorny:
>> On 8/9/22 10:50, Thomas de Groot wrote:
>>> Op 9-8-2022 om 14:53 schreef Thomas de Groot:
>>>> initially, I wanted to concentrate on the hdr light sources though...
>>>>
>>> ...and when I do, no photons are generated!
>>>
>>> I use
>>>    photons {
>>>      refraction on
>>>      reflection on
>>>    }
>>>
>>> for the sphere with the hdr map, identical to the code for the light 
>>> source. Decreasing spacing down to a ridiculously small value doesn't 
>>> change anything. I must be missing something here...
>>>
>>
>> I'm perhaps not following, but...
>>
>> Taking your hdr sphere to be an actual hollow sphere, you are making 
>> it a photon target for any photon light sources by adding the photon 
>> block above. In other words - as far as I know - there is no way to 
>> shoot photons from other than a traditional light sources.
>>
>> Aside: I've never tried to shoot photons from a light source inside a 
>> hollow object at the inside surface of that object. I'm not sure it 
>> would work given the how the radial 'shooting pattern' is aimed at 
>> target objects. Perhaps this the reason why you get no photons? Hmm, 
>> maybe a spot light would work... Too long since I've played with photons.
>>
>> Bill P.
> Unfortunatelly, Bill seems to be right. I tried a bit, but it seems to 
> be impossible to persuade a HDRI light to cast photons, so we need POV 
> 4.0 ;)
> 

That was also the conclusion I reached.

POV 4.0, where are you? :-)

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Glass for v3.8 finish features
Date: 10 Aug 2022 04:27:15
Message: <62f36be3$1@news.povray.org>
Op 9-8-2022 om 17:18 schreef Chris R:
> This is why I love working with POV and this community.  There's always someone
> who has thought about the same problems and is willing to share their experience
> (and code!)
> 

I uploaded my scene file in p.b.scene-files (same subject line).

Enjoy!

-- 
Thomas


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From: Alain Martel
Subject: Re: Glass for v3.8 finish features
Date: 10 Aug 2022 11:42:41
Message: <62f3d1f1$1@news.povray.org>
Le 2022-08-09 à 10:50, Thomas de Groot a écrit :
> Op 9-8-2022 om 14:53 schreef Thomas de Groot:
>> initially, I wanted to concentrate on the hdr light sources though...
>>
> ...and when I do, no photons are generated!
> 
> I use
>    photons {
>      refraction on
>      reflection on
>    }
> 
> for the sphere with the hdr map, identical to the code for the light 
> source. Decreasing spacing down to a ridiculously small value doesn't 
> change anything. I must be missing something here...
> 

The HDR map never emit photons.
What you can do to get caustics from an HDR map is to use radiosity. As 
the surface receiving the caustics is close to the objects causing it, 
your radiosity settings can still be lenient. You only a small 
error_bound value.

Try this as a starter :

global_settings{ assumed_gamma 1
	radiosity{
		error_bound 0.1 // may try smaller
		count 150 1111
		low_error_factor 0.2
		pretrace_end 0.005
		}
	}


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From: Alain Martel
Subject: Re: Glass for v3.8 finish features
Date: 10 Aug 2022 11:45:14
Message: <62f3d28a@news.povray.org>
Le 2022-08-09 à 08:43, Thomas de Groot a écrit :
> Op 9-8-2022 om 11:40 schreef Mr:
>> Was it slow to render ? There seems to be no anti aliasing.
>>
> I used +a0.3 +am2 +bm2 +bs8  maybe not the best aa setting but I was 
> playing ;-)
> 
> I think total render time was about 2 hours or a bit more.
> 

Just using +a0.1 instead of +0.3 should improve the result and should 
not increase the rendering time to much.


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From: Thomas de Groot
Subject: Re: Glass for v3.8 finish features
Date: 11 Aug 2022 11:25:34
Message: <62f51f6e@news.povray.org>
Op 10-8-2022 om 17:42 schreef Alain Martel:
> The HDR map never emit photons.
> What you can do to get caustics from an HDR map is to use radiosity. As 
> the surface receiving the caustics is close to the objects causing it, 
> your radiosity settings can still be lenient. You only a small 
> error_bound value.
> 
> Try this as a starter :
> 
> global_settings{ assumed_gamma 1
>      radiosity{
>          error_bound 0.1 // may try smaller
>          count 150 1111
>          low_error_factor 0.2
>          pretrace_end 0.005
>          }
>      }

Excellent suggestion, concentrating on the caustics! Thanks Alain. This 
is the result with:

error_bound      0.01
low_error_factor 0.1
pretrace_start  8/max(image_width,image_height)
pretrace_end    1/max(image_width,image_height)

and stochastic render:

+am3 +a0.01 +ac0.90 +r3

render time was only about 10 minutes.
-- 
Thomas


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