Saturn's atmosphere needs updating

General discussion about Celestia that doesn't fit into other forums.
Topic author
Kolano

Saturn's atmosphere needs updating

Post #1by Kolano » 29.02.2004, 17:54

The latest images from Cassini indicate we need some changes to Suturn's atmosphere definition.

Image
http://ciclops.lpl.arizona.edu/PR/2004B25/PR2004B25A.html

Can anyone suggest better settings?

Here's a Cel URL to take one to my guesitimate of Saturn being in the same position in Celestia...
cel://Follow/Sol:Saturn/2004-02-27T04:12:01.99901?x=AKbMArUxeE2gDA&y=iiWhrc8joLz+/////////w&z=la4jcFr0cUl0/////////w&ow=0.839040&ox=0.085886&oy=0.527160&oz=-0.103624&select=Sol:Saturn&fov=41.514980&ts=-1.000000<d=0&rf=38819&lm=130

Increasing the "height" to around 3000 seems to provide the lighter band seen at the top of the planet, but it also puts a band around the base of the planet for me, which is not seen in the real image.

Also this image seems to indicate that Celestia's ring shadows are not dark enough. They look much darker to me in the real image than they appear in Celestia.

Guest

Post #2by Guest » 29.02.2004, 17:59

Grr... I think screwed up the Cel URL somehow since it ends up looking at the sun for me rather than at Saturn.

Avatar
selden
Developer
Posts: 10136
Joined: 04.09.2002
With us: 18 years
Location: NY, USA

Post #3by selden » 29.02.2004, 19:11

Your URL works fine for me.

Also, you may have missed the comment on the CSICLOPS' "approach page" that
The image contrast and colors have been slightly enhanced to aid visibility.


That makes it a little hard to judge how much change would be appropriate. It's clear the opacity of the rings in Celestia isn't high enough, though.
Selden

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #4by t00fri » 29.02.2004, 21:57

Hi all,

below I compare the Saturn texture that I made a few months ago (from Bjorn Johnsson's recent 2k data)
in comparison with the very latest Cassini true color photo (see above).

Not so bad altogether, but we see a most important deficiency: The opacity of the rings is far too low in Celestia (you see the planet shining through on the top right!). This implies that the planet is too bright in the top half, since the shadows of the rings are not dark enough...We got some work to do here...

In case you have'nt spotted it right away, the top one is from Celestia :D
You may also observe that the rings need quite a bit of tuning: The outer rings (rel. to Cassini) are not dark enough and the separations of the inner ones are also not correctly modelled...

Bye Fridger

Image

JackHiggins
Posts: 1034
Joined: 16.12.2002
With us: 17 years 9 months
Location: People's Republic Of Cork, Ireland

Post #5by JackHiggins » 29.02.2004, 23:21

And it looks like the ring shadows (ring onto planet) need to be made much darker too...
- Jack Higgins
Jack's Celestia Add-ons
And visit my Celestia Gallery too!

granthutchison
Developer
Posts: 1863
Joined: 21.11.2002
With us: 17 years 10 months

Post #6by granthutchison » 29.02.2004, 23:57

JackHiggins wrote:And it looks like the ring shadows (ring onto planet) need to be made much darker too...
Jack, if the rings are made less transparent, then the ring shadows will get darker automatically. We don't want to make the shadows darker without fixing the rings, because that'll just look weird.

Grant

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #7by t00fri » 01.03.2004, 00:04

JackHiggins wrote:And it looks like the ring shadows (ring onto planet) need to be made much darker too...


Jack,

that's of course, one of the main issues which was discussed recently in the developer forum...

There was other independent (but less direct) information already that in Celestia, the opacity of the rings is too low and thus the darkness of the ring shadows insufficient. This (final) photo underlines the issue further, although the amount of processing always remains an unknown...

Bye Fridger

JackHiggins
Posts: 1034
Joined: 16.12.2002
With us: 17 years 9 months
Location: People's Republic Of Cork, Ireland

Post #8by JackHiggins » 01.03.2004, 23:32

grant wrote:Jack, if the rings are made less transparent, then the ring shadows will get darker automatically. We don't want to make the shadows darker without fixing the rings, because that'll just look weird.


:oops: Whoops... That was pretty obvious...
- Jack Higgins

Jack's Celestia Add-ons

And visit my Celestia Gallery too!

danielj
Posts: 1477
Joined: 15.08.2003
With us: 17 years 1 month

Post #9by danielj » 02.03.2004, 00:44

Not so bad,but a strip is missing.i don?t think the problems are only the rings.The Saturn texture could be improved as well.When Cassini gets near the planet,maybe we will soon have a 4k texture.Am I right?

below I compare the Saturn texture that I made a few months ago (from Bjorn Johnsson's recent 2k data)
in comparison with the very latest Cassini true color photo (see above).

Not so bad altogether, but we see a most important deficiency: The opacity of the rings is far too low in Celestia (you see the planet shining through on the top right!). This implies that the planet is too bright in the top half, since the shadows of the rings are not dark enough...We got some work to do here...

In case you have'nt spotted it right away, the top one is from Celestia :D
You may also observe that the rings need quite a bit of tuning: The outer rings (rel. to Cassini) are not dark enough and the separations of the inner ones are also not correctly modelled...

Bye Fridger

Image[/quote]

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #10by t00fri » 02.03.2004, 11:20

danielj wrote:Not so bad,but a strip is missing.i don?t think the problems are only the rings.The Saturn texture could be improved as well.When Cassini gets near the planet,maybe we will soon have a 4k texture.Am I right?


But you sure realize that the Saturn "surface" we are seing is not solid but gaseous and thus the "bands" may also change with time...like in case of Jupiter.

Of course, a 4k resolution would be a great step forward...

Bye Fridger

Toti
Developer
Posts: 338
Joined: 10.02.2004
With us: 16 years 7 months

Post #11by Toti » 02.03.2004, 16:43

The subtle purple "atmosphere light-scattering" effect is also interesting.
Instrumenting this in Celestia will be a great advance in simulation quality.

Bob Hegwood
Posts: 1048
Joined: 19.10.2003
With us: 16 years 11 months
Location: Germantown, Ohio - USA

Post #12by Bob Hegwood » 02.03.2004, 22:30

If you don't mind me saying so...

I think the Celestia Project is doing an incredible job of
getting us as close to the real thing as it does. When you stop
and think about what we're looking at here, it's simply mind-boggling
to me that it's as realistic as it is. :wink:

If this is going to turn into a wish-list for Saturn though, I'd like to see
the "spokes" and "patterns" of the rings in a better model.

Take care, Bob
Bob Hegwood
Windows XP-SP2, 256Meg 1024x768 Resolution
Intel Celeron 1400 MHz CPU
Intel 82815 Graphics Controller
OpenGL Version: 1.1.2 - Build 4.13.01.3196
Celestia 1.4.0 Pre6 FT1

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #13by t00fri » 02.03.2004, 22:49

Bob Hegwood wrote:If you don't mind me saying so...

I think the Celestia Project is doing an incredible job of
getting us as close to the real thing as it does. When you stop
and think about what we're looking at here, it's simply mind-boggling
to me that it's as realistic as it is. :wink:

If this is going to turn into a wish-list for Saturn though, I'd like to see
the "spokes" and "patterns" of the rings in a better model.

Take care, Bob


Grant is already working on it, I guess...

Bye Fridger

granthutchison
Developer
Posts: 1863
Joined: 21.11.2002
With us: 17 years 10 months

Post #14by granthutchison » 02.03.2004, 23:10

t00fri wrote:Grant is already working on it, I guess...
:)
Well, a while back Chris did suggest that we could someday have circumferential as well as radial detail in ring textures (a broad ring texture would be wrapped around the planet, so that things like eccentric rings and spokes might be better modelled). But until then you're going to have to be content with radial detail.
I've just pieced together an opacity map of the rings at 10km resolution (taken directly from star-occultation data), which should help get the shadows right - the B ring is pretty much opaque over much of its width, which accounts for the density of the ring shadow visible in the photograph. Just need to get an albedo map together that is correctly proportioned, and we should be cooking.

Grant

Bob Hegwood
Posts: 1048
Joined: 19.10.2003
With us: 16 years 11 months
Location: Germantown, Ohio - USA

Post #15by Bob Hegwood » 02.03.2004, 23:19

Cool... 8)

Thanks for your efforts here, Grant. :lol:

Take care, Bob
Bob Hegwood

Windows XP-SP2, 256Meg 1024x768 Resolution

Intel Celeron 1400 MHz CPU

Intel 82815 Graphics Controller

OpenGL Version: 1.1.2 - Build 4.13.01.3196

Celestia 1.4.0 Pre6 FT1

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #16by t00fri » 02.03.2004, 23:31

granthutchison wrote:
t00fri wrote:Grant is already working on it, I guess...
:)
Well, a while back Chris did suggest that we could someday have circumferential as well as radial detail in ring textures (a broad ring texture would be wrapped around the planet, so that things like eccentric rings and spokes might be better modelled). But until then you're going to have to be content with radial detail.
I've just pieced together an opacity map of the rings at 10km resolution (taken directly from star-occultation data), which should help get the shadows right - the B ring is pretty much opaque over much of its width, which accounts for the density of the ring shadow visible in the photograph. Just need to get an albedo map together that is correctly proportioned, and we should be cooking.

Grant


Grant,

very interesting, indeed!
At the level of radial info only, what's wrong with the Cassini albedo:

Image

JackHiggins
Posts: 1034
Joined: 16.12.2002
With us: 17 years 9 months
Location: People's Republic Of Cork, Ireland

Post #17by JackHiggins » 03.03.2004, 15:43

Great work grant! Hope to see this in a pre version sometime soon!
- Jack Higgins

Jack's Celestia Add-ons

And visit my Celestia Gallery too!

danielj
Posts: 1477
Joined: 15.08.2003
With us: 17 years 1 month

Post #18by danielj » 03.03.2004, 16:12

I still think that the colors are not accurate.We can improve Saturn's atmosphere definition.The yellow band near the equatorial zone is weekly seen.The trnsitions for the band are more subtle,not so abrupt,the polar zones are bigger and there isn't so purple near the poles.Anyway,if you remember,Hubble's photo was a little different.Anyway,there is still one big trouble : You can see stars in the dark side of the planets,it's such as the nightside of the planet was part of the sky.This is very weird.And the shadow of the rings in the planet are also lacking
t00fri wrote:Hi all,

below I compare the Saturn texture that I made a few months ago (from Bjorn Johnsson's recent 2k data)
in comparison with the very latest Cassini true color photo (see above).

Not so bad altogether, but we see a most important deficiency: The opacity of the rings is far too low in Celestia (you see the planet shining through on the top right!). This implies that the planet is too bright in the top half, since the shadows of the rings are not dark enough...We got some work to do here...

In case you have'nt spotted it right away, the top one is from Celestia :D
You may also observe that the rings need quite a bit of tuning: The outer rings (rel. to Cassini) are not dark enough and the separations of the inner ones are also not correctly modelled...

Bye Fridger

Image

Avatar
t00fri
Developer
Posts: 8772
Joined: 29.03.2002
Age: 18
With us: 18 years 5 months
Location: Hamburg, Germany

Post #19by t00fri » 03.03.2004, 17:45

danielj wrote:I still think that the colors are not accurate.We can improve Saturn's atmosphere definition.The yellow band near the equatorial zone is weekly seen.The trnsitions for the band are more subtle,not so abrupt,the polar zones are bigger and there isn't so purple near the poles.Anyway,if you remember,Hubble's photo was a little different.Anyway,there is still one big trouble : You can see stars in the dark side of the planets,it's such as the nightside of the planet was part of the sky.This is very weird.And the shadow of the rings in the planet are also lacking

...


I certainly agree that it makes sense to update Saturn's appearance to the latest photographic evidences. I will certainly do it. My image above was pre Cassini photograph.

But there is also no reason to hurry, since there is an attached warning that the public Cassini photos should not be used for scientific purposes (i.e. for Celestia :D), since the image is not yet properly "balanced"/normalized.

Bye Fridger

granthutchison
Developer
Posts: 1863
Joined: 21.11.2002
With us: 17 years 10 months

Post #20by granthutchison » 06.03.2004, 00:31

danielj wrote:You can see stars in the dark side of the planets,it's such as the nightside of the planet was part of the sky.
That's a moon of Saturn, crossing the planet's disc.

Grant


Return to “Celestia Users”

Who is online