Sun Tzu <sun### [at] nospamhotmailcom> wrote in message
news:3eb11c63$1@news.povray.org...
> Thank you for the suggestion.  I will try using media, although I must
> confess I'm rather confused about the difference between the media
> absorption parameters as opposed to the fade_power, fade_distance,
> fade_color specifications.  Isn't the fade_... stuff supposed to do the
same
> thing as the media absorption stuff?   If not, what is the difference and
> when should I use one instead of the other?
>

Okay, I'll admit that I didn't know either just off the top of my head.  So
I went and made this, after re-reading the documentation of course.

Okay, furthest to the left is media absorption,  The media absorbs green
blue and some red light (<.5,1,1>) and so the shadow is white minus half the
red, and all the rest (<.5,0,0>).

in the middle is fade.  In the fade there is no media, the fade_distance is
.5 (the radius of the sphere is 1), the fade_power is 1.5 (docs said use a
number between 1 and 2 so...), fade_color is <1,0,0> so all red (I tried
<0,1,1> but this blocked all red light...).

The sphere on the right is just a red sphere with filter and transmit of .75
and caustics on.

So!  Absorption absorbs light, and fade blocks light.  I think you could
achive similar effects using either... except that absorbing media can be
applied at with a density map, so where media is thickest it will absob the
most light.

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