Am 10.01.2018 um 11:49 schrieb Motive17:
> Good morning to all,
> 
> I'm focusing on a quite strange issue.
> 
> I have simply defined this light source:
> 
>     light_source {
>                  <0,500,-1000>
>                  color rgb <255, 255, 255>
>                  fade_distance 1
>                  fade_power 0
>                  media_interaction off
>                  media_attenuation off
>                      }
...
> The strange issue is relative to the behaviour of the light reflected by the
> cylinder. It seems to increase when I increase the distance between object and
> light source. Why? There is any light attenuation defined.

If you move the light source in the z direction only, then as you
increase the distance, the direction of the light source is getting
closer and closer to -z, so the light source gets closer and closer to
being perpendicular to the cylinder's axis.

Thus the lit portion of the cylinder is illuminated more vertically
(with respect to the cylinder surface, not the "world").

The diffuse component of a surface becomes brighter as the surface is
illuminated more vertically.

If it was just a matter of direction, this would be perfectly realistic.


In real life, the illumination from a light source also gets dimmer as
the distance increases. To simulate this properly, you should use
`fade_power 2`.

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