Hi Tracers!

I posted this several days ago but wonder why there have been no replys
at all... so I start another try...

Recently I started working out a scenario for a semi-fictitious
extrasolar planetary system (based on private sci-fi fantasies tracing
back to my 70s childhood) in PoV-Ray... I started with its largest
planet, a gas giant orbiting 300 million kms from the star.

As an astronomy geek, I'm familiar with both Earth-based and spaceborne
images of our "gas giants", e. g. Jupiter, Saturn, Uranus and Neptune.
So I made a concept of a Jupiter-like atmosphere marked by multicolored
latitudonal cloud bands , alternating with transparent zones through
which deeper cloud layers are visible, with elliptical storm systems
also in different colors and sizes (such as the Great Red Spot or the
smaller, less long-lived white or brownish cyclones on Jupiter)
scattered over the planet, on top wispy white ammonia ice clouds (and
perhaps later also a thin shell of bluish media haze, such as the bright
atmospheric fringe seen from Earth orbit -> "Afghan Sunrise", September
2000).

The colors of the very first version of Tmirdlalg turned out to be way
too flashy, the latest Cassini image of Jupiter reminded me that the gas
giants' actual colors as they would be seen on site by an astronaut with
unaided eye are in fact much more subdued (our concept of the planets
may be spoiled by the countless NASA images in blazing computer-enhanced
colors...), so I reworked the texture layers, using now less saturated
(and partially brighter) colors.

But there still remain some problems with the cyclones, for which I used
a Leopard pattern: firstly, they are obviously not randomly distributed,
but in regular patterns (for example the four evenly spaced large pale
orange storm systems around the center of the planet's disk), and
secondly, with the Leopard pattern, I only could create concentric cloud
bandings within the cyclones, but not spiralling ones as it would be
natural. Further, I would like to have them in random colors (within
certain limits), without building dozens of texture layers each of them
with but one single cyclone.

Some months ago, I experimented with the black hole warp feature for the
first time, and I think that it would roughly meet my desires... but I
remember the features inside the warps being densely squeezed towards
the center, which again would not look like a real cyclone.

Is there a better way to do "Great Red Spots"?

See you in Khyberspace!

Yadgar

***
"Living on the dole ain't sexy!" (G. Leadman in "The Bus to Kabul")

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Attachments:
Download 'tmir0003.jpg' (82 KB)

Preview of image 'tmir0003.jpg'

"Yadgar" <j.b### [at] ndhnet> wrote in message news:3A5### [at] ndhnet...

No comments? Well, it happens (you post, you check back every few hours,
your post just sits there uncommented and unnoticed, you wonder why everyone
hates you, you start to drink, your wife leaves you, your dog leaves you,
your mother pretends she doesn't know who you are....).

As to the image, the main problem at first glance is the hardness of the
edges of your spots. Try using a more gradual transition at the boundaries -
i.e.

not [0.70 A_Colour][0.70 Transparent]
but [[0.65 A_Colour][0.75 Transparent]

I like the main pigment, but the spots, to be honest, are fairly hideous at
the moment.

In the end, I would have thought that you would need a lot more interaction
between your bands and your spots - are you sure that warps can't help you?
I don't think I've ever used them myself, but they sound perfect for this
kind of thing.

If that fails, I guess it's time for an iso-pigment.

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Tom Melly wrote:

> "Yadgar" <j.b### [at] ndhnet> wrote in message news:3A5### [at] ndhnet...
>
> No comments? Well, it happens (you post, you check back every few hours,
> your post just sits there uncommented and unnoticed, you wonder why everyone
> hates you, you start to drink, your wife leaves you, your dog leaves you,
> your mother pretends she doesn't know who you are....).
>
> As to the image, the main problem at first glance is the hardness of the
> edges of your spots. Try using a more gradual transition at the boundaries -
> i.e.
>
> not [0.70 A_Colour][0.70 Transparent]
> but [[0.65 A_Colour][0.75 Transparent]
>
> I like the main pigment, but the spots, to be honest, are fairly hideous at
> the moment.
>
> In the end, I would have thought that you would need a lot more interaction
> between your bands and your spots - are you sure that warps can't help you?
> I don't think I've ever used them myself, but they sound perfect for this
> kind of thing.
>
> If that fails, I guess it's time for an iso-pigment.

I agree I make a post, and no one seems to care, except sometimes the people who
seem to comment on everything.  Really aren't  many of us posting just for a
sense that somebody cares.  If say you show an incredibly well rendered sphere
with a simple background to a family member you share your house with they might
so "ok", but they won't, can't understand the significance of it.  They don't
know that the texture was really hard to do, and took you hours or days to
perfect, and they won't try to understand either.  Here though things are
different, if we can't figure out how you did it in our heads it is impressive.
I am going to start responding to more posts, and I hope people respond to my
bad posts too.

Well I also agree that the spots are not very good yet.  Basically you are
trying to model a hurricane larger than the Earth.  I have read about computer
models of tornados, and they are very complicated.  Maybe you can use a fractal
like a mandlebrot set.  Or a slice of a julia set made out of media.  Fractals
are inherently infinitely complicated.

Dan Johnson

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In article <3A5### [at] ndhnet>, Yadgar <j.b### [at] ndhnet> wrote:

> I posted this several days ago but wonder why there have been no replys
> at all... so I start another try...

Your first article posted just fine...you should go back and cancel it, 
because articles do not expire on this group and the duplication just 
wastes server space.
As for the lack of responses...be a bit more patient. The first post was 
just a few days ago. Some subjects get faster responses than others.

You might want to try the blob pattern (or possibly the blob pigment) in 
MegaPOV on a layered texture to get the "eyes". The spiral pattern could 
be combined with this to make a spiraling texture that covers a specific 
spot.
As you mentioned, your storms are far too regularly placed...they also 
have very sharp edges, too much color variation, too little size 
variation, and don't overlap well. You should be able to use the blob or 
spherical patterns and layered textures to fix most of these problems.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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I would suggest maybe place warps behind each of the spots so the cloud bands
go around it, then just blend the edges a little with pigment_map.

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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>

I like the colors but after all of the layed pattern effects, the result is
visually static.  Maybe its that the blotches seem to fall into a regular and
nearly symmtric relation to the sphere.

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