Am 09.09.2015 um 00:53 schrieb Alain:

>> Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
>>> On 2015-09-02 09:49 AM (-4), clipka wrote:
>>>> I would recommend using a non-zero fade_distance, set to be equal to
>>>> the
>>>> corresponding object's radius. That more closely mimicks the
>>>> characteristics of a non-point light source.
>>>
>>> Is this true even for area_illumination with circular orient?
>>
>> Hum - that's a good question I've never thought about. But by extension
>> of what I said, if you model a single non-point light source as an array
>> of smaller light sources, then those smaller light sources'
>> fade_distance should be set equal to their radius, so for a highly
>> subdivided area_illumination light source the fade_distance should
>> indeed probably be close to zero.
> 
> But, if I remember the documentation correctly, setting fade_distance to
> zero effectively turn light fading off.
> 
> So, a very small, but non-zero, value is required.

That used to be the case indeed. As of POV-Ray 3.7.1, however,
fade_distance can be set to 0 for effect: The distance-based fading will
then follow a true inverse power law (effective_brightness =
nominal_brightness / (distance^fade_power)) rather than POV-Ray's
traditional fading formula; nominal brightness will be achieved at unit
distance.

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