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Apologies if this has been asked before, but (and I seem to recall
reading somewhere that ideally the only property of intensity,
fade_power, and fade_distance that would need to be changed to be
accurate to reality would be /intensity/) what, if any, unit of
luminosity is appropriate to apply to a light source if 1 POV-unit=1 m
and fade_power and fade_distance are both set to 1.0? Does the
resulting variable of intensity have any real-world analog, or is there
any defined conversion factor? Even an approximation would be useful.
Thanks!
--
Tim Cook
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El Wed, 03 Nov 2010 01:48:38 -0500, Tim Cook escribió:
> [..] I seem to recall
> reading somewhere that ideally the only property of intensity,
> fade_power, and fade_distance that would need to be changed to be
> accurate to reality would be /intensity/
Yes, but for that to be realistic, fade_power should be 2: intensity is
inversely proportional to the square of the distance from the source.
> what, if any, unit of
> luminosity is appropriate to apply to a light source if 1 POV-unit=1 m
> and fade_power and fade_distance are both set to 1.0? Does the
> resulting variable of intensity have any real-world analog, or is there
> any defined conversion factor? Even an approximation would be useful.
I researched this topic years ago, and I found it too complicated for
just artistic purposes... all that matters really is that all lights must
have realistic attenuation. Also, if you have several lights which are
supposed to have different intensities, the difference in intensity
should be realistic. So, for example, you can use real lumens data as the
intensity for your lights, scaling the data to adjust the brightness of
your image.
But if you're trying to match a scene lighting level with something
measured from reality, the best way would be to first perform tests
against a real scene, "a la" cornell box, to obtain that "conversion
factor".
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org
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> Apologies if this has been asked before, but (and I seem to recall
> reading somewhere that ideally the only property of intensity,
> fade_power, and fade_distance that would need to be changed to be
> accurate to reality would be /intensity/) what, if any, unit of
> luminosity is appropriate to apply to a light source if 1 POV-unit=1 m
> and fade_power and fade_distance are both set to 1.0? Does the resulting
> variable of intensity have any real-world analog, or is there any
> defined conversion factor? Even an approximation would be useful.
>
> Thanks!
>
> --
> Tim Cook
fade_power MUST be 2 to have a real world correlation. Any other value
is unrealistic.
A fade_power 1 is applicable in a 2D world, or to represent a very long,
infinitely long, and thin light source: A line light as opposed to a
point light.
A fade_power 3 would be realistic in a 4D world where the fourth
dimention is NOT time.
fade_distance is absolutely arbitrary.
You can try the lightsys macro collection. It contains many equivalences
for various kinds of real life light sources according to various colour
spaces, observator models,...
Alain
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On 2010-11-03 18:30, Alain wrote:
> A fade_power 1 is applicable in a 2D world, or to represent a very long,
> infinitely long, and thin light source: A line light as opposed to a
> point light.
For some reason I had it in my head that Moray's use of 1 for its light
fade_power was equivalent to a 'true' fade_power of 2...else why would
it default to 1? Hrmmm.
--
Tim Cook
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On 04/11/2010 7:45 AM, Tim Cook wrote:
> why would it default to 1?
point it out during Beta testing :-P
--
Best Regards,
Stephen
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On 2010-11-04 07:18, Stephen wrote:
> point it out during Beta testing :-P
Could be, could be...though I'd think 0 fade_power would be the
/simplest/ light model... ;)
--
Tim Cook
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On 05/11/2010 1:37 AM, Tim Cook wrote:
> On 2010-11-04 07:18, Stephen wrote:
>> point it out during Beta testing :-P
>
> Could be, could be...though I'd think 0 fade_power would be the
> /simplest/ light model... ;)
>
So would I, if my brain had been working properly :-(
--
Best Regards,
Stephen
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