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28 Mar 2024 09:20:01 EDT (-0400)
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From: Paolo Gibellini
Subject: Re: shattered certainties
Date: 14 Mar 2018 12:14:36
Message: <5aa94a6c$1@news.povray.org>
Norbert Kern wrote on 13/03/2018 12:53:
> Paolo Gibellini <p.g### [at] gmailcom> wrote:
> 
>> A significant scene.
>> Paolo
> 
> 
> 
> Many thanks, Paolo.
> 
> When will we see some new images from you?
> 
> Norbert
> 
> 
> 
Ha! You are right...
I've changed somehow my job and the pov-time has been absorbed into the 
new tasks, but I have not stopped putting aside new ideas.
Before the end of the spring I should be able to post something.
;-)
Paolo


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From: Norbert Kern
Subject: Re: shattered certainties
Date: 15 Mar 2018 17:55:01
Message: <web.5aaaeb5b2916df36304316810@news.povray.org>
Alain <kua### [at] videotronca> wrote:
>
> Using intervals 1 and tripling the samples value would have been much
> faster.
> You ONLY use intervals >1 when using method 1 or 2, never ever with
> method 3 (default).
>
> It probably have taken less than a day using intervals 1 and 10 times as
> many samples.


You are right with the intervals 1 issue.
If it wasn't a Gilles Tran code, i'ld have checked more carefully...

Meanwhile I rendered with intervals 1 and samples 70.
It's not faster, but the result is slightly better.

Norbert


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From: Norbert Kern
Subject: Re: shattered certainties
Date: 15 Mar 2018 18:00:00
Message: <web.5aaaec0f2916df36304316810@news.povray.org>
"s.day" <s.d### [at] uelacuk> wrote:

> Wow, this is an amazing scene. Making me want to dust off my povray skills (hope
> I haven't forgotten too much).
>
> Sean


Hi Sean,

it's time to come back...

Norbert


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From: Norbert Kern
Subject: Re: shattered certainties
Date: 15 Mar 2018 18:05:01
Message: <web.5aaaed482916df36304316810@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
>
> Ah, I see now too Gilles did have it there. Thanks.
>
> I got a couple small renders done yesterday - with and without the
> emission - and compared them. At a high level adding in emission the
> color of the background sky makes the clouds look as if they are sitting
> in a hazy atmosphere without having modeled the hazy atmosphere. See the
> attached image.
>
> The difference image on the right shows an aspect or pitfall of the
> method - depending on one's goal I suppose. Once one or more color
> channels for the media 'interval' being sampled is maxed out (Red here),
> you get a 'disjoint' color-hue change in the media due the emission
> adder.
>
> >
> > I remember your image - very impressive.
>
> Thanks - though I certainly don't play in your artistic league. :-)
>
> Bill P.

Interesting. I wouldn't have thought the effect of small emission value is that
strong. I've to do more tests...

Norbert


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From: Stephen
Subject: Re: shattered certainties
Date: 15 Mar 2018 18:12:45
Message: <5aaaefdd$1@news.povray.org>
On 15/03/2018 21:56, Norbert Kern wrote:
> "s.day" <s.d### [at] uelacuk> wrote:
> 
>> Wow, this is an amazing scene. Making me want to dust off my povray skills (hope
>> I haven't forgotten too much).
>>
>> Sean
> 
> 
> Hi Sean,
> 
> it's time to come back...
> 
> Norbert
> 

Seconded!


-- 

Regards
     Stephen


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From: Norbert Kern
Subject: Re: shattered certainties
Date: 15 Mar 2018 18:20:00
Message: <web.5aaaf1742916df36304316810@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:
>
>
> Wow, very nice! I like the poofy-yet-hazy clouds and the grass especially.
>
> :)
>
>
> Mike

Thanks Mike,

the grass is an old mesh I used in my "boreal" image
(http://hof.povray.org/Boreal_big.html). Here I subdivided the mesh via PoseRay
-a very useful tool.

The 8 bit heightfield was enhanced by the method of Jaimes Vives Piqueres to get
a more detailed HF map
(http://www.ignorancia.org/en/index.php?page=Heightfield_based_Isosurfaces).

Norbert


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From: Dan Byers
Subject: Re: shattered certainties
Date: 15 Mar 2018 20:45:00
Message: <web.5aab13242916df3682045b180@news.povray.org>
"Norbert Kern" <nor### [at] t-onlinede> wrote:
> a comment on the present conditio humana.
>
>
> Norbert

Nicely done!  I salute you :D

Dan
roadkillpuppy.com


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From: William F Pokorny
Subject: Re: shattered certainties
Date: 19 Mar 2018 13:31:23
Message: <5aaff3eb$1@news.povray.org>
On 03/15/2018 06:01 PM, Norbert Kern wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
...
>>
>> I got a couple small renders done yesterday - with and without the
>> emission - and compared them. At a high level adding in emission the
>> color of the background sky makes the clouds look as if they are sitting
>> in a hazy atmosphere without having modeled the hazy atmosphere. See the
>> attached image.
>>
>> The difference image on the right shows an aspect or pitfall of the
>> method - depending on one's goal I suppose. Once one or more color
>> channels for the media 'interval' being sampled is maxed out (Red here),
>> you get a 'disjoint' color-hue change in the media due the emission
>> adder.
>>
...
> 
> Interesting. I wouldn't have thought the effect of small emission value is that
> strong. I've to do more tests...
> 
> Norbert
> 
> 
Sorry slow - busy with real life.

Emission is stronger by nature because the emission intensity increases 
with depth of media. If you want to 'sort of' match a scattering 
intensity with an emission media, you have to add absorption at about 
the same value as the emissive value (1).

I've always used scattering+absorption, emission+absorption or 
emission+scattering. Never all three - intentionally at least - as 
Gilles did here (2).

Bill P.

(1) - An idea on my to play with list is some method to pre-render or 
pre-calculate scattering with attenuation media so as to be able to 
create a faster emission+absorption or a scattering without attenuation 
+ absorption media model for use in follow-on renders.

(2) - I've wondered some recently about whether POV-Ray should support 
two absorption specifications given Gilles technique looks useful.


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From: William F Pokorny
Subject: Re: shattered certainties
Date: 19 Mar 2018 14:03:29
Message: <5aaffb71@news.povray.org>
On 03/15/2018 05:53 PM, Norbert Kern wrote:
> Alain <kua### [at] videotronca> wrote:
> 
> You are right with the intervals 1 issue.
> If it wasn't a Gilles Tran code, i'ld have checked more carefully...
> 
> Meanwhile I rendered with intervals 1 and samples 70.
> It's not faster, but the result is slightly better.

Thanks for running again this way and reporting the speed! Your result 
lines up with my recent experience and what I see in the media code as 
I've been trying to digest it. In the code, intervals and samples end up 
both combining to drive the number of initial samples taken.

If you need 70 initial samples to resolve the smaller/rapid changes in 
your cloud or your shadows - you need them - no matter the intervals / 
samples combination to get them and the performance won't be much 
different due the initial specification. In some ways needing a higher 
number of initial samples with a media is like needing a high 
max_gradient value with isosurfaces due the function used.

In any case, intervals 1 is the way to go with method 3 for quality 
always - and often enough the 'density/shadow function' will be such 
that the adaptive method 3 with intervals 1 and a low samples setting is 
much, much faster.

Bill P.


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From: Thomas de Groot
Subject: Re: shattered certainties
Date: 20 Mar 2018 03:57:53
Message: <5ab0bf01$1@news.povray.org>
On 19-3-2018 18:31, William F Pokorny wrote:
> On 03/15/2018 06:01 PM, Norbert Kern wrote:
>> William F Pokorny <ano### [at] anonymousorg> wrote:
> ...
>>>
>>> I got a couple small renders done yesterday - with and without the
>>> emission - and compared them. At a high level adding in emission the
>>> color of the background sky makes the clouds look as if they are sitting
>>> in a hazy atmosphere without having modeled the hazy atmosphere. See the
>>> attached image.
>>>
>>> The difference image on the right shows an aspect or pitfall of the
>>> method - depending on one's goal I suppose. Once one or more color
>>> channels for the media 'interval' being sampled is maxed out (Red here),
>>> you get a 'disjoint' color-hue change in the media due the emission
>>> adder.
>>>
> ...
>>
>> Interesting. I wouldn't have thought the effect of small emission 
>> value is that
>> strong. I've to do more tests...
>>
>> Norbert
>>
>>
> Sorry slow - busy with real life.
> 
> Emission is stronger by nature because the emission intensity increases 
> with depth of media. If you want to 'sort of' match a scattering 
> intensity with an emission media, you have to add absorption at about 
> the same value as the emissive value (1).
> 
> I've always used scattering+absorption, emission+absorption or 
> emission+scattering. Never all three - intentionally at least - as 
> Gilles did here (2).
> 
> Bill P.
> 
> (1) - An idea on my to play with list is some method to pre-render or 
> pre-calculate scattering with attenuation media so as to be able to 
> create a faster emission+absorption or a scattering without attenuation 
> + absorption media model for use in follow-on renders.
> 
> (2) - I've wondered some recently about whether POV-Ray should support 
> two absorption specifications given Gilles technique looks useful.


Aha! This is an interesting notion I was not aware of. I am going to 
follow that up. Thanks!

-- 
Thomas


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