As I see it, you can abserve several effects:
1. media_attenuation isn't used, since there's no fog or media anywhere
2. The darker red appearing underneath your planes-objects is actually
 the shadow of the planes, colored due to fade_color
3. If you lower fade_distance, you can see that though the pure-diffuse
cylinder gets darker red, the one with a little ambience looks washed
out. There's probably some way in how ambient and fade's are calculated
which ultimately result in that ambient 1 object to be pure white.
3b. With lowered fade_distance (to .2 e.g.) there is no sudden gap when
the cylinder pokes out of the planes anymore, cause it is colored entirely
red near-bottom and the shadow is too.

Fiddle around a bit with fade_distance, the lightsource position
and where the shadows fall, and you'll get an understanding what
happening.


--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: Tim### [at] gmxde

> As for the media, you didn't forget the hollow, no?
> I'll take a look at the scene now.
>
> --
> Tim Nikias v2.0
> Homepage: http://www.digitaltwilight.de/no_lights
> Email: Tim### [at] gmxde
>
> > In this scene:
> >
> > global_settings { assumed_gamma 1.0 }
> > camera { location  <1.5, 3, 3> look_at <1.5, -1, 0> }
> > light_source { 10000, rgb 1 media_attenuation on }
> > intersection { plane { y, 0 } plane { -y, 2 } pigment { transmit 1 }
> >   interior { fade_power 1001 fade_distance 2 fade_color <1, 0, 0> } }
> > cylinder { <3, 2, 0>, <3, -4, 0>, .3 pigment { rgb 1 } }
> > cylinder { <2, 2, 0>, <2, -4, 0>, .3 pigment { rgb 1 }
> >   finish { ambient 0 diffuse 1 } }
> > cylinder { <1, 2, 0>, <1, -4, 0>, .3 pigment { rgb 1 }
> >   finish { ambient 1 diffuse 0 } }
> > cylinder { <0, 0, 0>, <0, -2, 0>, .3 pigment { blue 1 } }
> >
> > The camera is looking down at three white cylinders, which pass through
a
> > two-unit clear layer with red-colored light attenuation in its interior.
> The
> > one on the left uses the default finish, the middle one has only diffuse
> 1,
> > and the right one has only ambient 1. (A fourth, blue cylinder simply
> marks
> > the height of the clear layer.)
> >
> > Notice the abrubt change in color at the bottom of the layer, in all
three
> > cylinders. This should not happen because the pigment is clear and the
> > attenuating interior should result in only continuous changes.
> >
> > Also, the ambient cylinder is completely white all the way to the bottom
> of
> > the layer. The attenuation is having no effect on it, except where it
> pokes
> > all the way through. The problem is visible in the default-finished
> cylinder
> > too.
> >
> > These problems are making attenuation pretty much useless for what I'm
> > trying to do (in particular, model some reasonable-looking water). So I
> > tried using absorbing media instead. But when I replace the interior
> > statement in the code above with:
> >   interior { media { absorption rgb <1, 0, 0> } }
> > absolutely nothing happens! All three cylinders are as white as ever.
> >
> > It doesn't seem possible to me that all these features could be so
> horribly
> > broken, but it seems that they are. Am I doing something wrong, or are
> these
> > bugs?
> >
> > Anders
> >
> >
>
>

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