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Kari Kivisalo wrote:
> Jaime Vives Piqueres wrote:
>> color LightColor*7*pow((DX+DZ)/2,2)
>> fade_distance 1
>>
>> and you will see they give the same scene!'
>
> Now scale the whole scene by 0.00001 and keep fade_distance 1 :)
> Use one source.
Hmmm... now I see it! I used a variable to scale down the entire scene
at will (including light color), and tested both methods. I found that
"fade_distance 1" and "sqrt(sqrt(area))" give the same results for anything
above 1, and both are constant (they give the same light at any scale above
1). For scales smaller than fade_distance, both start to give wrong
results: with "fade_distance 1" light loses more and more intensity, while
"sqrt(sqrt(area))" behaves the contrary, but not so hardly.
Then, can this means the POV attenuation formula is not really
appropriated for values bellow 1? Anyhow, as I assumed a scale of 1 unit =
1 cm for my macro, this not really important: any of both methods works
fine.
But in the meanwhile, I found that srqt(sqrt(area)) permits a more
intuitive use of my MAX_LUMENS variable, so I will use it with your
permision. :)
> The equation used in pov clearly tries to estimate the combined axial near
> field of multiple point sources on planar surface. fade_distance tells the
> size of the source.
Hmmm... then this is why it is different from the typical inverse square
law for point sources? This will be very helpful on the official docs. The
current explanation is somewhat "difficult to understand" for mere mortals.
Thanks for your explanations, Kari: fade_distance was the more intriguing
part of light_sources for me.
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org
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