I just started playing with the save_file option in Mega-POV 0.4, to
save my radiosity values. I was wondering what can I change in the
scene or in the way the scene is rendered, and still be able to use
the saved radiosity file.

In other words, if I add a few objects to a scene, I expect that I
would probably *not* be able to reuse the radiosity data. Is this
correct?

Can I switch antialiasing on or off, and still reuse the data?

Can I render the image at a small size, saving the radiosity values,
and then reuse these values in a larger final render size?

It would be really great to create a test render at a smaller size,
without antialiasing, and save the radiosity values. Then change to a
larger final image size with antialiasing, and reuse the previous
radiosity settings. Would this work? Are there any drawbacks to this
idea, or potential problems to watch out for?

Thanks,
Glen Berry

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Glen Berry <7no### [at] ezwvcom> wrote:
: In other words, if I add a few objects to a scene, I expect that I
: would probably *not* be able to reuse the radiosity data. Is this
: correct?

  Yes. The radiosity data would be wrong because those new objects have not
been taken into account.
  I don't know if it's completely invalid, or if you can use the saved data
anyways. This might be the case when the additional objects have unnoticeable
effect on the global illumination.

: Can I switch antialiasing on or off, and still reuse the data?

  I think yes.

: Can I render the image at a small size, saving the radiosity values,
: and then reuse these values in a larger final render size?

  Probably. The quality may suffer, though.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Glen Berry <7no### [at] ezwvcom> wrote...

> In other words, if I add a few objects to a scene, I expect that I
> would probably *not* be able to reuse the radiosity data. Is this
> correct?

You can, but, as Warp said, the illumination would be at least slightly
incorrect.

> Can I switch antialiasing on or off, and still reuse the data?

Yes.

> Can I render the image at a small size, saving the radiosity values,
> and then reuse these values in a larger final render size?

Yes.  When you re-use the values, it will still generate more if necessary.
You can even use save_file and load_file at the same time, and when you
render the scene over and over again, it will keep increasing the total
amount of data that it has.  It will re-use the old data and add more data
to produce a more accurate solution.  You can use "always_sample no" if you
want to only use the data that you load and you don't want any new samples
to be taken.

-Nathan

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Can this data be used in a continue trace? Do you use the +c option, or just
add load_file to the radiosity section? I read through the MegaPov help
file, but it wasn't specific.

Grim
gri### [at] isonet

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GrimDude <vos### [at] yahoocom> wrote ...
> Can this data be used in a continue trace? Do you use the +c option, or
just
> add load_file to the radiosity section? I read through the MegaPov help
> file, but it wasn't specific.

If you had the radiosity disk cache turned on and you use the +c option to
continue, then POV will automatically load the data that it saved (apart
from save_file).  If you also do a load_file with a continued trace, you'll
probably have redundant data in the system (which shouldn't make anything
look bad, but will take up more memory and will probably slow things down a
bit).

-Nathan

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> If you had the radiosity disk cache turned on ...

Now I'm really confused. How do you turn the radiosity disk cache on?

Apparently, the help file isn't clear, or I need to read it from beginning
to end...

Grim

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GrimDude <vos### [at] yahoocom> wrote...
> > If you had the radiosity disk cache turned on ...
>
> Now I'm really confused. How do you turn the radiosity disk cache on?
>
> Apparently, the help file isn't clear, or I need to read it from beginning
> to end...
>

I guess it is always on.  POV always writes radiosity data to a temporary
file called <scene_name>.RCA.

Internally, there's a variable called
"opts.Radiosity_File_SaveWhileRendering", but for some reason it is always
set to true.

-Nathan

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