Bruno Cabasson wrote on 06/12/2019 13:48:
> 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
> 

This one is very realistic, perhaps it needs a few work near the horizon.

Paolo

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