Celestia Forums

Hi all,

since Frank asked me yesterday to send him my personal 2k
Saturn texture setup, I thought that after some Cassini
imaging update, it might also be interesting for others.

Here it is as ZIP archive (1.4 MB) for public download from
my TextureFoundry site:

http://www.shatters.net/~t00fri/Saturn.zip

The attached, relevant section from Celestia's solarsys.ssc,
saturn.ssc, is to give an idea about the way I prefer to
illuminate my Saturn texture...Since I use the OpenGl 2.0
rendering path, others may see slight differences when
displaying it with different renderings.

What is special about it?

It is originally based on Bj?¶rn J??nsson's great
1800x900 texture, http://www.mmedia.is/~bjj/,
however, with colors adapted to recent published
'natural color' imaging from the Cassini mission:

a) Southern hemisphere:
-------------------------------------
http://photojournal.jpl.nasa.gov/catalog/PIA05389
http://photojournal.jpl.nasa.gov/catalog/PIA06155
http://photojournal.jpl.nasa.gov/catalog/PIA06114
http://photojournal.jpl.nasa.gov/catalog/PIA06060

b) Northen hemisphere (strong enhancement of blue! NEW):
----------------------------------------------------------------------------

http://photojournal.jpl.nasa.gov/catalog/PIA06176
http://photojournal.jpl.nasa.gov/catalog/PIA06177


Saturn's rings essentially correspond to Celestia's default.
They were built by Grant Hutchison from Cassini imaging, with
transparency information carefully derived from stellar transit
data obtained from:

http://pds-rings.arc.nasa.gov/ringocc/ringocc.html

Perhaps, it's worth making a few comments how I updated
my texture to incorporate the strikingly blue northern
hemisphere:

A warm-up for GIMP affectionados


I loaded my original 2k cylindrical texture into GIMP and
opened a new transparent layer on top of it, however with a
height of only 512 pixels, i.e. only extending from the north
pole to the equator. Then I loaded the beautiful Cassini
'natural color ' image ( PIA06176.tif, see above) showing the
whole range of "northern blues" (cf. inlet mage below). I
next made a gradient with ends matching the color
range as taken from that Cassini image. Furthermore, by clicking
with the right mouse button on that active top layer in GIMP's layer dialog, I opened
a new white(i.e. untransparent) mask for that layer of
'blue shades'. With Gimp's gradient tool, I then drew the blue
gradient vertically across the layer and another black-> white
gradient vertically across the corresponding layer mask. This effects a
smooth blending-in of the blue layer starting from the equator
and getting total around the north pole. That's all.

The result you see on this 800x400 mini-texture:


The full 2k texture is in my ZIP archive, of course.

Here is a preview from Celestia. Note in 4 years from now
(2009), the top of Saturn is fully illuminated and the blue
shades fully visible. This is illustrated in the bottom image.



Enjoy,

Bye Fridger

Fridger,

Looks like a nice texture for use with the current Saturnian season. I would be a bit cautious however about displaying this in 2009. Perhaps by then the seasonal change will start to turn the northern hemisphere less blue. Some guidance on this might be had from looking at previous images (even from Earth) at times when Saturn's rings were edgewise?

scalbers wrote:Fridger,

Looks like a nice texture for use with the current Saturnian
season. I would be a bit cautious however about displaying
this in 2009. Perhaps by then the seasonal change will start
to turn the northern hemisphere less blue. Some guidance on
this might be had from looking at previous images (even
from Earth) at times when Saturn's rings were
edgewise?

Steve,

my 2009 image above was less a prediction than a way of
displaying the /present/ shading of blue in full illumination.
You are right I should have emphasized this more clearly.

Being a physicist, I think I understand the reason for that
blue color quite well. It is based on the known wavelength
dependence of light scattering in the atmosphere.

Indeed, in 2009 it's better to make a new texture , since
the illumination i.e. the sun's light path through the northern
atmosphere and illumination angle will be very different.
Also throughout, it is assumed that the northern atmosphere
is largely cloud free. It is unknown why this is so. The cloud
coverage may well change in 2009. In Celestia we usually
ignore seasonal changes of cloud coverage both on Earth (
see however DonEdward's textures) and clearly also on
Saturn .

According to my understanding, the apparent color will
substantially depend on the observation angle relative to the sun!
In a similar fashion that on Earth the sky looks blue or red or
whitish, depending on where the sun is positioned and where
we are looking.

Hence earthbound observations concerning Saturn's
northern atmosphere color when the rings are edgewise, are
most probably different from what an observer can
see who looks from the point corresponding to my image
above! This angular dependence of the color is fully
understood, but hard to implement into Celestia's display .

Cheers,

Bye Fridger

Thanks Fridger. Excellent textures.

They really match the photos and look spectacular.

Because these are truly realistic, I would recommend that as an aid to all the folks who don't know much about editing the main solarsys.ssc file or placing the textures into medres, you simply make it an add-on by placing a "Replace" command on the Saturn.ssc file that comes with your download, renaming and moving the 2 textures into a medres folder within the add-on, and mentioning in your read-me file that downloaders should simply place the add-on into their extras folder.

Alternatively, I have already made the changes so that it acts as an add-on. If you wish, I can upload it to Motherlode for you, or send it to you via e-mail to save you the time.

Let me know your desires here.


Frank

fsgregs wrote:Thanks Fridger. Excellent textures.

They really match the photos and look spectacular.

Because these are truly realistic, I would recommend that as
an aid to all the folks who don't know much about editing the
main solarsys.ssc file or placing the textures into medres,
you simply make it an add-on by placing a "Replace"
command on the Saturn.ssc file that comes with your
download, renaming and moving the 2 textures into a medres
folder within the add-on, and mentioning in your read-me file
that downloaders should simply place the add-on into their
extras folder.

Alternatively, I have already made the changes so that it acts
as an add-on. If you wish, I can upload it to Motherlode for
you, or send it to you via e-mail to save you the time.

Let me know your desires here.

Frank

Frank,

many thanks for your suggestions! A very good idea. I think
it is easiest, if I make the modifications directly to my ZIP
archive in the TextureFoundry, since I am not much "at home"
at the ML.

The modifications are easy enough...

Bye Fridger

t00fri wrote:

fsgregs wrote:Because these are truly realistic, I would recommend that asan aid to all the folks who don't know much about editing themain solarsys.ssc file or placing the textures into medres,
you simply make it an add-on by placing a "Replace"
command on the Saturn.ssc file that comes with your
download, renaming and moving the 2 textures into a medres
folder within the add-on, and mentioning in your read-me file
that downloaders should simply place the add-on into their
extras folder.Frank

Frank,many thanks for your suggestions! A very good idea. Bye Fridger

Be careful, Franck, Fridger:
Yes, it is a better way to organize alternate textures/addons: to edit a folder that must be install in 'extras' (or another subfolder like 'solar system' in it, with this contents: .ss file, readme/info file and textures/medres or hires folder.
BUT, the .ssc file, as I understand these new commands, must be a 'Modify' one (with just the usefull lines: the first one (beginning with 'Modify'), and the textures and rings items for the sat example.
The 'Replace' one must contain ALL the sub-obJects lincked with the main planet: with only the planet Replace infos, no object related to is drawn by Celestia, as I had experimented with my install (re-packaging some addons in this way)
The 'Replace' function is onlya good tool to replace a singleton, not a complex system, isn't it???
So, thanks for the Jupi and Sat texture, Fridger, they're very impressives, Jeam.

Jeam Tag and Fridger:

Yep, you are right. "Replace" cannot be used for Saturn.

Fridger, as an aid to you, I have changed your Saturn.ssc file to Modify. Here is your code that differs from the Celestia default:

Modify "Saturn" "Sol"
{
Texture "saturn2.png"
SpecularColor [ 0.23 0.256 0.195 ]
SpecularPower 35.0
HazeColor [ 0.8 0.66 0.4 ]
HazeDensity 0.5

Rings {
Texture "saturn-rings2.png"
}
}


I renamed your two textures so that they could be placed in an add-on medres folder, instead of replacing the default textures.

Thanks again to all of you. These textures really look excellent.

Frank

Thanks Frank and Jeam for your help & suggestions!

I have now replaced the Saturn.zip with a respective add-on
'saturn.zip' that only needs to be unzipped in the extras folder
in order to work. I could not see, Frank, why I would have to
rename saturn.png etc.

Could someone, please, download the archive
and test its proper function under Windows! Under
Linux everything works fine.

Here is the download URL:

******************************************
http://www.shatters.net/~t00fri/saturn.zip
******************************************

Enjoy,
Bye Fridger

PS:
As soon as this is confirmed to work, I shall upload my new
4k Titan in the same way...

t00fri wrote:
PS:
As soon as this is confirmed to work, I shall upload my new
4k Titan in the same way...

Yes, as a Windows XP user, I can confirm that all has worked fine.

TERRIER wrote:

t00fri wrote:
PS:
As soon as this is confirmed to work, I shall upload my new
4k Titan in the same way...

Yes, as a Windows XP user, I can confirm that all has worked fine.

Thanks TERRIER!

so now let's get at uploading Titan 4k also as a 'Modify' add-on.


Bye Fridger

t00fri wrote:so now let's get at uploading Titan 4k also as a 'Modify' add-on.Bye Fridger

Hello Fridger,Win XP too, poor graphic card: it works fine, like the test I've organized with your first upload for my install before posting my previous message. Your Jupiter is running well in the same way, too.I'm waiting for your superb Titan. Thanks, Jeam

Fridger:

I have now replaced the Saturn.zip with a respective add-on
'saturn.zip' that only needs to be unzipped in the extras folder
in order to work. I could not see, Frank, why I would have to
rename saturn.png etc.

I had always assumed that if an ssc file in an extras folder called up a texture that was already in the main medres folder of Celestia, that the program would load that main texture (e.g. - Saturn.png) from the existing medres folder and would ignore any replacement texture by the same name that was in the extras add-on folder. Someone once told me the order of choice for Celestia was always to check the main textures folder first.

Apparently, this has changed, and a Modify command in an extras folder ssc file will now direct Celestia to ignore the texture in the main textures folder, and load the texture in the add-on file instead, even if they are the same name.

You learn something every day.

By the way, folks keep talking about your Jupiter texture. Is that the one that has been on your website for well over a year, or have you done a more recent update to Jupiter?

Frank