I believe that fade_power = 2 is "correct", light is 1/4 power at double
the distance. Others will know for sure.
Dolan wrote:
> I'm wondering -- which value of fade_power is physically accurate?
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
Dolan wrote:
> > I'm wondering -- which value of fade_power is physically accurate?
None are.
Real light attenuation is proportional to
1/(d^2)
The closest you can get with POV is fade_power 2 (and
fade_distance 1), which is proportional to
1/( (1+d/(fade_distance))^fade_power )
or
1/( (1+d)^2 )
As d gets larger, this approximation looks more and more like the
real thing.
-Nathan
