POV-Ray : Newsgroups : povray.general : Is there a way to collect environment data? Server Time: 19 Oct 2017 10:48:49 GMT
  Is there a way to collect environment data? (Message 1 to 7 of 7)  
From: Fudz4
Subject: Is there a way to collect environment data?
Date: 26 Feb 2017 14:10:01
Message: <web.58b2e13d905b4ff01279700f0@news.povray.org>
I am currently dispersing photons in a pov ray environment, however what I would
like to do is collect properties of each photon and their interactions with the
scene, in other words collect information on each photon trajectory. How do you
think i could go about doing this?

Thank you very much.


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From: Alain
Subject: Re: Is there a way to collect environment data?
Date: 26 Feb 2017 16:27:35
Message: <58b301f7@news.povray.org>
Le 17-02-26 à 09:07, Fudz4 a écrit :
> I am currently dispersing photons in a pov ray environment, however what I would
> like to do is collect properties of each photon and their interactions with the
> scene, in other words collect information on each photon trajectory. How do you
> think i could go about doing this?
>
> Thank you very much.
>
>
>

Photons are only stored at the location where they hit an object or 
interact with scattering media.

The way I do something similar to what you seems to want to do without 
using media:
Reduce your scene to be mostly 2 dimentionnal.
Place a white plane as a background. Make it «finish{brilliance 0 
ambient 0}» so that it's illumination is independent fom the direction 
of the light hitting it.
Make sure that your light goes very slightly toward that plane.
Place your optical elements.

This will show you the path of your photons.

The photons that you see always stop where they show.

This is MUCH faster than using media, but don't work if the path of the 
photons is 3 dimentionnal.


Alain


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From: Fudz4
Subject: Re: Is there a way to collect environment data?
Date: 27 Feb 2017 15:25:01
Message: <web.58b44413ff4596b04b918b6e0@news.povray.org>
Alain <kua### [at] videotronca> wrote:
> Le 17-02-26 à 09:07, Fudz4 a écrit :
> > I am currently dispersing photons in a pov ray environment, however what I would
> > like to do is collect properties of each photon and their interactions with the
> > scene, in other words collect information on each photon trajectory. How do you
> > think i could go about doing this?
> >
> > Thank you very much.
> >
> >
> >
>
> Photons are only stored at the location where they hit an object or
> interact with scattering media.
>
> The way I do something similar to what you seems to want to do without
> using media:
> Reduce your scene to be mostly 2 dimentionnal.
> Place a white plane as a background. Make it «finish{brilliance 0
> ambient 0}» so that it's illumination is independent fom the direction
> of the light hitting it.
> Make sure that your light goes very slightly toward that plane.
> Place your optical elements.
>
> This will show you the path of your photons.
>
> The photons that you see always stop where they show.
>
> This is MUCH faster than using media, but don't work if the path of the
> photons is 3 dimentionnal.
>
>
> Alain

Thanks for the reply, yo said that photons are 'stored' at the location they
land, is there a way to collect that data? I am tasked with using a machine
learning algorithm to estimate the light density for example.


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From: clipka
Subject: Re: Is there a way to collect environment data?
Date: 27 Feb 2017 17:09:09
Message: <58b45d35$1@news.povray.org>
Am 27.02.2017 um 16:21 schrieb Fudz4:

> Thanks for the reply, yo said that photons are 'stored' at the location they
> land, is there a way to collect that data? I am tasked with using a machine
> learning algorithm to estimate the light density for example.

There used to be a mechanism for saving photon data, for re-use in
subsequent renders. Search for "save_file" and "load_file" photon settings.

I'm afraid this mechanism is still dysfunctional in POV-Ray 3.7.x, so
you may have to fall back to 3.6 instead.


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From: Alain
Subject: Re: Is there a way to collect environment data?
Date: 28 Feb 2017 21:17:24
Message: <58b5e8e4@news.povray.org>
Le 17-02-27 à 12:09, clipka a écrit :
> Am 27.02.2017 um 16:21 schrieb Fudz4:
>
>> Thanks for the reply, yo said that photons are 'stored' at the location they
>> land, is there a way to collect that data? I am tasked with using a machine
>> learning algorithm to estimate the light density for example.
>
> There used to be a mechanism for saving photon data, for re-use in
> subsequent renders. Search for "save_file" and "load_file" photon settings.
>
> I'm afraid this mechanism is still dysfunctional in POV-Ray 3.7.x, so
> you may have to fall back to 3.6 instead.
>

What do you mean by dysfunctional?
I routinely use that feature and did not encouter any obvious isue.


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From: Jim Holsenback
Subject: Re: Is there a way to collect environment data?
Date: 1 Mar 2017 11:36:13
Message: <58b6b22d$1@news.povray.org>
On 2/28/2017 4:17 PM, Alain wrote:
> Le 17-02-27 à 12:09, clipka a écrit :
>> Am 27.02.2017 um 16:21 schrieb Fudz4:
>>
>>> Thanks for the reply, yo said that photons are 'stored' at the
>>> location they
>>> land, is there a way to collect that data? I am tasked with using a
>>> machine
>>> learning algorithm to estimate the light density for example.
>>
>> There used to be a mechanism for saving photon data, for re-use in
>> subsequent renders. Search for "save_file" and "load_file" photon
>> settings.
>>
>> I'm afraid this mechanism is still dysfunctional in POV-Ray 3.7.x, so
>> you may have to fall back to 3.6 instead.
>>
>
> What do you mean by dysfunctional?
> I routinely use that feature and did not encouter any obvious isue.

yep .... i was thinking the same thing


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From: clipka
Subject: Re: Is there a way to collect environment data?
Date: 1 Mar 2017 16:24:15
Message: <58b6f5af$1@news.povray.org>
Am 01.03.2017 um 12:36 schrieb Jim Holsenback:
> On 2/28/2017 4:17 PM, Alain wrote:
>> Le 17-02-27 à 12:09, clipka a écrit :
>>> Am 27.02.2017 um 16:21 schrieb Fudz4:
>>>
>>>> Thanks for the reply, yo said that photons are 'stored' at the
>>>> location they
>>>> land, is there a way to collect that data? I am tasked with using a
>>>> machine
>>>> learning algorithm to estimate the light density for example.
>>>
>>> There used to be a mechanism for saving photon data, for re-use in
>>> subsequent renders. Search for "save_file" and "load_file" photon
>>> settings.
>>>
>>> I'm afraid this mechanism is still dysfunctional in POV-Ray 3.7.x, so
>>> you may have to fall back to 3.6 instead.
>>>
>>
>> What do you mean by dysfunctional?
>> I routinely use that feature and did not encouter any obvious isue.
> 
> yep .... i was thinking the same thing

Sorry, my bad - in the process of verifying that the mechanism is alive
and kicking, I confused the parser code for radiosity
`save_file`/`load_file` with that for photon mapping
`save_file`/`load_file`.

Since the code in question no longer does anything except print a parse
warning saying that INI file options must be used nowadays (which is
indeed true for radiosity), but there are no such INI file options for
photon mapping, I erroneously concluded that photon save/load cannot
possibly be functional.

(Which begs the question why the bloops someone insisted that radiosity
had to use INI file options, when the SDL statements were apparently
good enough for photon mapping. I know I'm to blame for actually
/implementing/ the radiosity changes, but I'm pretty damn sure it wasn't
my call back then.)


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