Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 06/12/2019 om 10:54 schreef Bruno Cabasson:
> > Hi there !
> >
> > Long time so see... I can't say I'm back, but after a while in hibernation
> > concerning POV-Ray, I recently revived my clouds. This render took 1h 45 mn on a
> > Xeon quad E5-1620 V2 @ 3.7GHz, with latest version 3.8 and with "+a0.05  +am3
> > +ac0.99 +r4".
> >
> > Regards
> >
>
> Good to see you here again indeed! Those clouds of yours were always my
> fovourites.
>
> --
> Thomas

Thanks Thomas! For my clouds, I was lacking specific built-in functions that can
express density for the medias involed within a spherical shell.

-) One for the atmosphere, an exponentially decreasing function like
A*exp(-kh/T), where k is the order of the funtion, h is the height wrt ground, T
is shell thickness, currently expressed as a function :

// Atmosphere density function A*exp(-kh/T), h being height wrt ground (whish it
were native ...). _R is the planet diameter at ground level.
#declare shell_exp = function (x, y, z, _h, _t, _a, _k, _R)
{
    _a*exp(-_k*(sqrt(x*x+(y+_R)*(y+_R)+z*z) - (_h + _R))/_t)
}

-) Another would be a series of classical patterns (wrinkles works quite fine),
but contained in a spherial shell. I hope it can be expressed mathematically.

-) And yet another would be a spherical shell shaped fog. I use scattering media
to imitate, but the behaviour is not really correct.


camera is at the edge of the media container but inside, or if it is just
outside. It has also implications with radiosity, so far I could see.


the rest is the same values, except the sun power and the parmeters for the fog
media. Colors are obtained automatically thanks to media, mainly the atmosphere
with rayleigh scattering.

Regards

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