Am 18.09.2015 um 20:57 schrieb MichaelJF:
> clipka <ano### [at] anonymousorg> wrote:
> 
>> Unless using an area_light with area_illumination on, fade_distance
>> should typically be roughly equal to the hypothetical radius of whatever
>> light source you are trying to simulate. So for instance, to simulate a
>> classic frosted E27 incandescent light bulb, and presuming you're using
>> a scale of 1m per POV-Ray unit for your scene, a fade_distance of 0.03
>> would be about the right value.
> 
> 
> 
> I wonder what part of the bulb determines this fade_distance: the frosted part,
> the diameter of the socket (E27) or the incandescent part? I suppose the power
> consumption given in Watt (Germany) with this kind of bulbs in former years and
> now replaced by lumen with energy saving lamps usually influence the general
> brightness only and not the fade_distance. The "incandescent" should influence
> the color of the light source, so only the "frosted" remains. 3 cm is the
> approximated radius of this bulbs and as they are frosted the point where their
> full light intensity should arise. Is this the reason for this fade_distance?

Exactly. As you get closer to the surface of the light bulb, the light
source gets more and more non-point-like, and the inverse square law
they teach us at school breaks down.

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