"Shuffle" <shu### [at] gmailcom> wrote:

> > Bald Eagle: Have a look at:
http://news.povray.org/povray.binaries.animations/thread/%3Cweb.5b32f0c22078c5ce458c7af
e0
> %40news.povray.org%3E/
> This is interesting, especially because I don't use POV 3.8 so I had a glimpse
> at new features ;-)
> I downloaded alpha9893777 and proceeded to render the (50 frames) animation: at
> no moment is the grey plane invisible behind or inside the media. I understand
> this is not the purpose of that scene, and the hidden sphere is actually hidden,
> but my need is to have an actually visible object, only hidden because of the
> density of the media.

The purpose there was to show how you can use 3 different functions to control
the color, by having a separate function for r, g, and b, and then adding them
together.

> Basically, what I want is exactly what happens in nature with fog: the objects
> are always there, but as you increase the distance to them, you can't see them
> anymore because the droplets absorb their light and diffuse that of the sun
> instead.

> Maybe I do not understand what you mean, but this does not change the fact that
> a constant density of 1 still allows seeing the sphere through the media. It is
> not a matter of color itself, I can pretty much set any color I want, including
> a color_map for the density, the object inside is always visible.
>
> What I would probably need are densities higher than 1, or something that mimics
> it.

YES.

>But since densities are looped in the 0-1 range, this is not possible with
> the current implementation of density, unless I missed something...

Don't count me as an expert - media can be, and usually is, a complicated thing
to use, especially properly/accurately.

http://www.povray.org/documentation/view/3.6.1/413/

"Imagine media as a density of particles, you specify 100 particles per cubic
pov-unit. If we scale a 1 cubic pov-unit object to be twice as big in every
direction, we will have a total of 800 particles in the object. The object will
look different, as we have more particles to look through. Yet the objects
density is still 100 particles per cubic pov-unit. In media this "particle
density" is set by the color after emission, absorption, or in the scattering
statement"

> PS: this is a professional need, so unfortunately I cannot let go...

I think what you need to do is a calibration scene, much like doing a
calibration exposure in the Zone System for making black & white prints.

Stretch a box across the screen, and define a wedge shape to hold your media.
That way you go from 0 - 100% in terms of "obscurement".
Then you can fiddle with the "density" of the media to find out at what point
you can no longer see through it.

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