Dolan wrote:
> 
> I'm wondering -- which value of fade_power is physically accurate?

  Since electromagnetic waves like light spread out evenly from their source
the intensity or strength is inversely proportional to the square of the
distance of the wave from it's source. In other words if the distance
travelled is 3, the intensity will be 1/9 the intensity when the distance
is 1.
 Comparing this formula to that listed in the docs it is safe to presume
that you need a value of fade distance_1 and fade_power 1, for a distance
of 1, for Pov to apply the law in a physically correct behaviour.
  Keep in mind when you area applying this that you understand the model.
This applies to an open candle flame that has nothing acting upon it to
reflect light back into itself. Most common light sources don't adhere to
the inverse square law because of filament properties, reflectors,
and shading devices. This leaves a little room for artistic license if
needed.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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