> 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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