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  megapov post-process question (Message 1 to 5 of 5)  
From: Tek
Subject: megapov post-process question
Date: 21 Feb 2006 03:50:43
Message: <43fad463@news.povray.org>
I have a problem, I want to render a scene on 2 different machines, but I'm 
using megapov's post-processing. The idea would be I render the scene 
normally on the first machine and upside down on the second machine, then 
stop it when there's a decent overlap, but megapov's post processing won't 
run if I stop the render!

So, does anyone know of a way to persuade megapov's post processing to run 
on a partial render? Or alternatively to make it operate on a previously 
rendered image? I notice it saves some files in the directory, so can I tell 
it to read them back in?

Apologies if the answer to this is in the docs, but I'm too busy trying to 
finish my IRTC entry to go look it up!

-- 
Tek
http://evilsuperbrain.com


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From: Christoph Hormann
Subject: Re: megapov post-process question
Date: 21 Feb 2006 04:40:03
Message: <dten12$iv4$1@chho.imagico.de>
Tek wrote:
> I have a problem, I want to render a scene on 2 different machines, but I'm 
> using megapov's post-processing. The idea would be I render the scene 
> normally on the first machine and upside down on the second machine, then 
> stop it when there's a decent overlap, but megapov's post processing won't 
> run if I stop the render!
> 
> So, does anyone know of a way to persuade megapov's post processing to run 
> on a partial render? 

No.  What you could however do (although this is a really scary hack) is 
to create a dummy 'first half' render using an empty scene, interrupt it 
and use it for initializing a continued trace of your actual scene.  Do 
the actual render of the first half on the second machine, interrupt it 
and continue it with the empty scene to finish and post process.

And finally put the two halfs together (AFAIK common interpretation of 
the IRTC rules does not consider this to be illegal post processing if 
you don't actually alter the image).

You will have to make sure you work with sufficient overlap between the 
two parts when you use a non-local post processing (like blur).

And i have no idea if post processing can actually be combined with 
continued trace without problems.

Christoph

-- 
POV-Ray tutorials, include files, Landscape of the week:
http://www.imagico.de/ (Last updated 31 Oct. 2005)
MegaPOV with mechanics simulation: http://megapov.inetart.net/


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From: Tek
Subject: Re: megapov post-process question
Date: 21 Feb 2006 12:53:13
Message: <43fb5389@news.povray.org>
Interesting suggestion, though if I understand you correctly that means I 
need to know where the halfway point in my image is. But if I know that I 
can just do a partial render on each machine of say 55% of the image, and 
the post processing will behave nicely, without any need to trick it into 
doing continued renders.

But if I do that it's guaranteed that one of my machines will finish faster 
than the other, because the top of my scene is slower. So what I'd like to 
do is start them both rendering and stop them once they overlap, that way I 
don't end up wasting any time waiting for one or other machine to finish!

Incidentally, I did continue a render the other day and discovered that the 
post-processing only gets applied to the continued part, not the whole 
image.

-- 
Tek
http://evilsuperbrain.com

"Christoph Hormann" <chr### [at] gmxde> wrote in message 
news:dten12$iv4$1@chho.imagico.de...
> Tek wrote:
>> I have a problem, I want to render a scene on 2 different machines, but 
>> I'm using megapov's post-processing. The idea would be I render the scene 
>> normally on the first machine and upside down on the second machine, then 
>> stop it when there's a decent overlap, but megapov's post processing 
>> won't run if I stop the render!
>>
>> So, does anyone know of a way to persuade megapov's post processing to 
>> run on a partial render?
>
> No.  What you could however do (although this is a really scary hack) is 
> to create a dummy 'first half' render using an empty scene, interrupt it 
> and use it for initializing a continued trace of your actual scene.  Do 
> the actual render of the first half on the second machine, interrupt it 
> and continue it with the empty scene to finish and post process.
>
> And finally put the two halfs together (AFAIK common interpretation of the 
> IRTC rules does not consider this to be illegal post processing if you 
> don't actually alter the image).
>
> You will have to make sure you work with sufficient overlap between the 
> two parts when you use a non-local post processing (like blur).
>
> And i have no idea if post processing can actually be combined with 
> continued trace without problems.
>
> Christoph
>
> -- 
> POV-Ray tutorials, include files, Landscape of the week:
> http://www.imagico.de/ (Last updated 31 Oct. 2005)
> MegaPOV with mechanics simulation: http://megapov.inetart.net/


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From: Tek
Subject: Re: megapov post-process question
Date: 23 Feb 2006 05:21:57
Message: <43fd8cc5$1@news.povray.org>
Just to update this thread: the question is academic now. To my considerable 
surprise I'm happy with my scene and I still have time for the final render 
(I think...) without needing to do any of this craziness.

-- 
Tek
http://evilsuperbrain.com

"Tek" <tek### [at] evilsuperbraincom> wrote in message 
news:43fad463@news.povray.org...
>I have a problem, I want to render a scene on 2 different machines, but I'm 
>using megapov's post-processing. The idea would be I render the scene 
>normally on the first machine and upside down on the second machine, then 
>stop it when there's a decent overlap, but megapov's post processing won't 
>run if I stop the render!
>
> So, does anyone know of a way to persuade megapov's post processing to run 
> on a partial render? Or alternatively to make it operate on a previously 
> rendered image? I notice it saves some files in the directory, so can I 
> tell it to read them back in?
>
> Apologies if the answer to this is in the docs, but I'm too busy trying to 
> finish my IRTC entry to go look it up!
>
> -- 
> Tek
> http://evilsuperbrain.com
>
>


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From: Tek
Subject: Re: megapov post-process question
Date: 1 Mar 2006 00:15:23
Message: <44052deb@news.povray.org>
On the off-chance anyone's still reading this thread, I answered my own 
question today. It is possible to run post processing on an aborted render, 
but you need to do some nasty trickery, here's what I did:
1/ Before aborting, I copied the *.ppd files that post processing creates.
2/ In a different folder I created a new scene file with the same name that 
contained just the post processing section of my scene.
3/ Rendered that scene and paused it just before megapov started the 
post-processing phase.
4/ Replaced the ppd files it had just made with the ones from the original 
aborted render.
5/ Unpaused, and it ran post processing on my original image!

Now, step 3 can't be timed perfectly so I ended up getting a bit of my empty 
scene at the bottom, but that's fine for my aborted render since I only had 
the top half of that one.

Way more work than it should be, I think the moral is: render to a 48-bit 
intermediate images and run post processing seperately...
-- 
Tek
http://evilsuperbrain.com

"Tek" <tek### [at] evilsuperbraincom> wrote in message 
news:43fad463@news.povray.org...
>I have a problem, I want to render a scene on 2 different machines, but I'm 
>using megapov's post-processing. The idea would be I render the scene 
>normally on the first machine and upside down on the second machine, then 
>stop it when there's a decent overlap, but megapov's post processing won't 
>run if I stop the render!
>
> So, does anyone know of a way to persuade megapov's post processing to run 
> on a partial render? Or alternatively to make it operate on a previously 
> rendered image? I notice it saves some files in the directory, so can I 
> tell it to read them back in?
>
> Apologies if the answer to this is in the docs, but I'm too busy trying to 
> finish my IRTC entry to go look it up!
>
> -- 
> Tek
> http://evilsuperbrain.com
>
>


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