Oh, and please note that the subject matter ("eithalica," the quadrupal planet)

POV-Ray has about posting copyrighted material on the newsgroup, but a thousand
thanks for your help with my scene settings.

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On 5-9-2011 1:26, Quartz wrote:
> Oh, and please note that the subject matter ("eithalica," the quadrupal planet)

> POV-Ray has about posting copyrighted material on the newsgroup, but a thousand
> thanks for your help with my scene settings.
>
>
Care to elaborate a bit on "eithalica"? Cannot be found on Google... 
(just curious)

Thomas

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> Alain<aze### [at] qwertyorg>  wrote:
>> Why is your sun and planets both at coordinate 0?
>
> The planet[s] should be in a union that's translated at the end.

Then, during the devlopment phase, place your sun some distance away. 
That way, the radiosity contribution will be visible and not totaly 
hiden by the direct illumination.

>
>> With 3.6.1, there was a bug in radiosity: The recursion level had to
>> take transparent surfaces into consideration. You have 4 athmospheric
>> layers and recursion_level default to 3. Then, you have two sets of
>> layers plus the actual surface, for a total of 9.
>
> Excellent! I think you've hit upon it, Alain! Thank you.

Another reason to use version 3.7...

>
>> That said, I realy think that you should use only one athmospheric shell
>> containing only scattering media. You then modulate the density of that
>> media as needed, using the spherical pattern scalled to the radius of
>> the athmonsphre or some custom function.
>
> Oh, I didn't realize we had a spherical pattern before! I will definitely
> investigate.
>
>> fade_power 10? for your athmosphere?
>> A realistic fade_power is 1 for substances to use linear fading, or 1001
>> to use the exponential formula.
>> Test without fading gives beter results.
>> It's fade_power 2 for a fading light_source.
>
> This was to replace extinction, because I wasn't artistically satisfied with
> realistic results. Still willing to work on that; I probably just didn't have it
> configured correctly.
>
> Thanks a lot, everyone! I might post more on this later, but my initial question
> has been answered.
>
>

Just a note about the spherical pattern:
It's centered at <0,0,0>
It's value is 1 (rgb<1,1,1>) at the origin and drop to zero at a radius 
of 1, then stay to zero everywhere.

There is also the onion pattern. It's a spherical gradient pattern. 
Start at zero at the origin and climb up to 1.

In your scene, you have a merge of all your athmospheric shells 
containing a single media.
You need to give an individual shell to each planet, apply the spherical 
pattern then place them into position.
Adjust the colour_map for the pattern to be 1 at the planetary surface 
and drop to zero at the very top of the shell.
Something like:
color_map{[Planet_Radius/Athmosphere_radius rgb 1][0 rgb 0]}

It's normal to take some artistic liberties when you model something 
that is physicaly impossible. That quadruple planet just can't exist, 
the center planet may survive, but the 3 moons would be ript apart by 
the gravitational gradient and degenarate into a massive ring of 
debrits. Think Saturn's rings, but about 10000 to 1000000 times denser.



Alain

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Thomas de Groot <tenDOTlnDOTretniATtoorgedDOTt> wrote:
> On 5-9-2011 1:26, Quartz wrote:
> > Oh, and please note that the subject matter ("eithalica," the quadrupal planet)

> > POV-Ray has about posting copyrighted material on the newsgroup, but a thousand
> > thanks for your help with my scene settings.
> >
> >
> Care to elaborate a bit on "eithalica"? Cannot be found on Google...
> (just curious)
>
> Thomas

I believe it appears in the comments in my scene code, and in the filenames of
some of the bitmaps used. Other copyrighted fictional names appear in the code
also.

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Alain <aze### [at] qwertyorg> wrote:

> > The planet[s] should be in a union that's translated at the end.
>
> Then, during the devlopment phase, place your sun some distance away.
> That way, the radiosity contribution will be visible and not totaly
> hiden by the direct illumination.

By "the end" I meant the end of the file or scene script, not the end of
development. The light source is very far away already, it's just also very
bright.

> Another reason to use version 3.7...

Indeed. I am hoping soon to look into what it would take to upgrade on Mac OS X
Lion.

> Just a note about the spherical pattern:
> It's centered at <0,0,0>
> It's value is 1 (rgb<1,1,1>) at the origin and drop to zero at a radius
> of 1, then stay to zero everywhere.

Thanks! So I read in the documentation.

Unfortunately, although this is very close to what I need, it won't give a
realistic exponential die-away curve like we see in earth's atmosphere:
http://en.wikipedia.org/wiki/Atmosphere_of_Earth#Pressure_and_thickness
I may need a custom function after all, but that is beyond my current
experience. I love learning new things, but it'll be a bumpy ride! ;)

> That quadruple planet just can't exist,
> the center planet may survive, but the 3 moons would be ript apart by
> the gravitational gradient and degenarate into a massive ring of
> debrits. Think Saturn's rings, but about 10000 to 1000000 times denser.

You're thinking of Roche's limit:
http://en.wikipedia.org/wiki/Roche%27s_limit

It's actually very interesting that you bring this up, because this was a
serious concern of mine when designing the planetary system. I worked out all
the physics according to my knowledge, and I think it could theoretically work.

Note that the planets make one full rotation (one day) in about 5 hours (4.70
hrs in my scene script). The system spins far, far faster than earth does, in
order to compensate for the greatly increased gravity.

When redesigning the bitmaps for the cloud layers, I'm going to have lots of fun
with the meteorological ramifications of a massively larger Coriolis effect,
among other things.

Again, this is all copyrighted by me, and thank you all so much for indulging
me! :)

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"Quartz" <qua### [at] malexmedianet> wrote:
> Thomas de Groot <tenDOTlnDOTretniATtoorgedDOTt> wrote:
> > On 5-9-2011 1:26, Quartz wrote:
> > > Oh, and please note that the subject matter ("eithalica," the quadrupal planet)

> > > POV-Ray has about posting copyrighted material on the newsgroup, but a thousand
> > > thanks for your help with my scene settings.
> > >
> > >
> > Care to elaborate a bit on "eithalica"? Cannot be found on Google...
> > (just curious)
> >
> > Thomas
>
> I believe it appears in the comments in my scene code, and in the filenames of
> some of the bitmaps used. Other copyrighted fictional names appear in the code
> also.


ever published any of it. Above, I mistakenly put the date that I invented it
and wrote it down.

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"Quartz" <qua### [at] malexmedianet> wrote:
> Indeed. I am hoping soon to look into what it would take to upgrade on Mac OS X
> Lion.

Uh-oh, looks like I'll have to compile from source if I want that to work...
Does that sound right?

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>> That quadruple planet just can't exist,
>> the center planet may survive, but the 3 moons would be ript apart by
>> the gravitational gradient and degenarate into a massive ring of
>> debrits. Think Saturn's rings, but about 10000 to 1000000 times denser.
>
> You're thinking of Roche's limit:
> http://en.wikipedia.org/wiki/Roche%27s_limit

Yes.

Anyway, those planets would be heavily distorted by the mutual 
gravitational pull.
The main planet would get strongly flatened at the poles and would 
probably show proeminent bulges toward the moons.
The moons would be ove shaped with the small end toward the main planet. 
(version 3.7 have an ove primitive)
The athmosphere can realisticaly connect all 4 worlds, allowing you to 
fly, or float, from one world to the other.

>
> It's actually very interesting that you bring this up, because this was a
> serious concern of mine when designing the planetary system. I worked out all
> the physics according to my knowledge, and I think it could theoretically work.

If the 4 planets have the same mass and density, the actual limit may be 
shorter, and the 2 oposite ones may help stabilise the third. But that 
system still looks fictional...

>
> Note that the planets make one full rotation (one day) in about 5 hours (4.70
> hrs in my scene script). The system spins far, far faster than earth does, in
> order to compensate for the greatly increased gravity.

Yep! Tidal lock between 4 bodies.

>
> When redesigning the bitmaps for the cloud layers, I'm going to have lots of fun
> with the meteorological ramifications of a massively larger Coriolis effect,
> among other things.
>
> Again, this is all copyrighted by me, and thank you all so much for indulging
> me! :)
>
>
>

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Alain <aze### [at] qwertyorg> wrote:
> Anyway, those planets would be heavily distorted by the mutual
> gravitational pull.

Yes, adding slight oblateness to the main planet and prolateness to its moons is
on my to-do list.

> The athmosphere can realisticaly connect all 4 worlds, allowing you to
> fly, or float, from one world to the other.

According to my calculations, at the surface of each planet/moon, the
acceleration due to gravity would not be too much less than on earth, in which
case the gap is far too large for a person to jump by themselves.

I'm not sure what the "escape velocity" would be though, because the gravity
falloff is greatly exaggerated from the norm by the body on the other side.
Perhaps a rocket would not be necessary.

> If the 4 planets have the same mass and density, the actual limit may be
> shorter, and the 2 oposite ones may help stabilise the third. But that
> system still looks fictional...

Of course I've never heard of NASA discovering a system like this in real life,
but I did try to be very careful in my calculations.

Would you like me to post the POV-Ray script for a simulation I did in order to
determine the free-fall acceleration in such a system?

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On 5-9-2011 21:04, Quartz wrote:
> "Quartz"<qua### [at] malexmedianet>  wrote:

> ever published any of it. Above, I mistakenly put the date that I invented it
> and wrote it down.
>
>

I see. Somewhat off topic but still curious: Do you intend to publish 
your work in some official way? Otherwise I wonder why you insist on 
copyright here. All/most scenes by all posters here are original works 
and - implicitly according to ruling etiquette - we acknowledge code 
from others when used. Or am I hopelessly naive? ;-)

Thomas

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