"Niels Boehm" <boh### [at] minetuni-jenade> wrote in message
news:Pin### [at] paxp12mipooluni-jenade...

i have been wondering whether the recent 3.5 version of POVray
features a different attenuation formula in comparison to 3.1a
(that's the version i have) ...

It has carried over the "more realistic attenuation" from MegaPOV 0.7.
Use it by specifying a number of 1000 or greater for 'fade_power'.

Well, actually, the formula in 3.1a is not bad, as it approximates
reality quite well, but it is not 100% correct ... it should be an
exponential decay - something like Inew = Iold * (e ** (- k * d)),
with e = 2.718.., ** = power, k = constant determining the strength
of attenuation, d = distance the ray had to take through the medium -
instead, shouldn't it?

Don't ask me.  ;-)
The doc says:  Attenuation = exp(-depth/fade_dist)
However, that's only for 'interior' and not for lights.  Light sources still
only use the usual linear, quadratic, etc., fading.

Bob H.

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