Hi.
I have some questions about the radiosity save_file and
load_file, hope someone can help.

If I'm pre-rendering with:
radiosity {
        ...
        save_file "mypic.rad"
        always_sample on
}
to get a save file, then
radiosity {
        ...
        load_file "mypic.rad"
        always_sample off
}
at a higher res for the final image, then:

1) do the saved radiosity data after the pretrace
of the first render get used in the final render?

2) is there any point in turning anti-aliasing on
for the first render?

I'm assuming 1) yes, and 2) no, for now :-)

-- 
Bill Hails
http://thyme.homelinux.net/

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> I have some questions about the radiosity save_file and
> load_file, hope someone can help.

Hi Bill!

What you want to do is the following: use pretrace_start 1 and pretrace_end
1 on the second pass where you load the data. There is no need for
pretracing when you're loading the data.

So, yes, the data gets used. always_sample on would introduce new samples in
the final render whenever POV-Ray's statistics (or whatever method it uses)
determine that an extra sample is needed. Especially for animations this can
add noise to the scene.

AFAIK, Antialiasing will only be used on the final render, not during the
pretracing, and as you should be using always_sample off, there shouldn't be
a need to use antialiasing on the first pass.

<shameless plug>
You might also want to have a look at my Radiosity-Experiment to be found
here:
http://www.nolights.de/past_pros/radiosity/radiosity.html
It not only covers what you've asked, but goes further and uses a method
that has been developed here in the newsgroups: smoothening the
radiosity-data on the second pass. It can reduce artifacts, but also loses
detail. As far as I'm concerned, less artifacts is better.
</shameless plug>

Regards,
Tim
-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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Tim Nikias v2.0 wrote:

>> I have some questions about the radiosity save_file and
>> load_file, hope someone can help.
> 
> Hi Bill!

Hi Tim.

> 
> What you want to do is the following: use pretrace_start 1 and
> pretrace_end 1 on the second pass where you load the data. There is no
> need for pretracing when you're loading the data.

Good tip, but are you saying that I must use "always_sample on" for the
second render? I was hoping to avoid that if possible.

> So, yes, the data gets used. always_sample on would introduce new samples
> in the final render whenever POV-Ray's statistics (or whatever method it
> uses) determine that an extra sample is needed. Especially for animations
> this can add noise to the scene.
> 
> AFAIK, Antialiasing will only be used on the final render, not during the
> pretracing, and as you should be using always_sample off, there shouldn't
> be a need to use antialiasing on the first pass.

Ah, but if I'm using "always_sample on" in the first pass, will that
interact with antialiasing at all when generating the radiosity
save file? and does it matter?

> <shameless plug>
> You might also want to have a look at my Radiosity-Experiment to be found
> here:
> http://www.nolights.de/past_pros/radiosity/radiosity.html
> It not only covers what you've asked, but goes further and uses a method
> that has been developed here in the newsgroups: smoothening the
> radiosity-data on the second pass. It can reduce artifacts, but also loses
> detail. As far as I'm concerned, less artifacts is better.

I'm bookmarking that page right now, and will read it avidly, thanks
for the pointers.

> </shameless plug>
> 
> Regards,
> Tim

-- 
Bill Hails
http://thyme.homelinux.net/

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> Ah, but if I'm using "always_sample on" in the first pass, will that
> interact with antialiasing at all when generating the radiosity
> save file? and does it matter?

AFAIK, yes, all Radiosity samples will be saved to disk once the render
completes, but I'm not 100% sure of that. I strictly switch always_sample
off on the second, to make sure that I don't get any random samples when
doing the smoothening mentioned in the link.
As for antialiasing: due to the antialiasing technique, POV-Ray will send
several more rays to a single pixel, and thus *might* find a point where it
wants another sample, which it wouldn't find if it weren't using
antialiasing. But then again, radiosity isn't really a per-pixel effect,
since the samples are spread almost evenly across the visible scene, so it
shouldn't really matter that much.

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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Tim Nikias v2.0 wrote:

>> Ah, but if I'm using "always_sample on" in the first pass, will that
>> interact with antialiasing at all when generating the radiosity
>> save file? and does it matter?
> 
> AFAIK, yes, all Radiosity samples will be saved to disk once the render
> completes, but I'm not 100% sure of that. I strictly switch always_sample
> off on the second, to make sure that I don't get any random samples when
> doing the smoothening mentioned in the link.
> As for antialiasing: due to the antialiasing technique, POV-Ray will send
> several more rays to a single pixel, and thus *might* find a point where
> it wants another sample, which it wouldn't find if it weren't using
> antialiasing. But then again, radiosity isn't really a per-pixel effect,
> since the samples are spread almost evenly across the visible scene, so it
> shouldn't really matter that much.
> 

Right, thanks, much clearer now, I've switched to "always_sample off"
in both passes.

I read your page, it just makes me realise I need to go back and re-read
the radiosity sections in the manual, and make notes :-)

> Regards,
> Tim
> 

-- 
Bill Hails
http://thyme.homelinux.net/

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