Planet Rings

[Andrew]

Hi all,
First of all let me say that I think Celestia is a great piece of software, I run help a small planetarium on the Isle of Wight (UK) we have a 5 metre dome and I am currently in the process of adding a new system using tutorials I have found on the net to project an image/video on the dome covering a wide area (using a mirror and a standard projector) I will add images when I get some where worth "shouting" about!
Anyway enough of that! I am tring to make a solar system tour show that is going well, but one thing I want to do is fly through Saturn's rings, which yes I can do the rings are flat is there any add-ons about that make the rings have some mass? so the user can see rocks etc.? If not I'm sure others may what this maybe its something that can be looked into for future releases.

Thank you

Andrew

[jestr]

Hi Andrew,as part of my Stargate-Bane addon on the Motherlode,I have made a gas giant planet called Repsilon,which has a ring system which has thousands of little ice rocks making up the rings,it wouldnt match exactly with Saturn though as the rings are a little different to Saturn's.You can download it from here
http://www.celestiamotherlode.net/catalog/show_addon_details.php?addon_id=695
check it out,cheers,Jestr

[bh]

I'd like very much if you could post a pic jestr me old.

[jestr]

OK,mate here's a shot from close to the rings


I think the ring particles may only be included in the hires version as it runs pretty slow on my PC.Jestr

[bh]

Nice! The rings look good too! Hehe.

[Andrew]

Thats cool thnx I might be able to use that to make some for Saturn, thanks alot
Andrew

[rthorvald]

Thats cool thnx I might be able to use that to make some for Saturn, thanks alot
Andrew

The most detailed, scientifically correct Saturn rings file we have is Fridger & Grant??s 2k saturnrings png file. I don??t know if there is a stand-alone anywhere, but you can extract it from my Saturn download, which you??ll find on Celestial Matters. Combine that with Jestr??s particles, and i think you will get a pretty stunning show...

BTW, that should not be too hard to do. Probably just have to modify the semimajor axis values in Jestrs ssc file and link it to Saturn.

- rthorvald

[t00fri]

...
The most detailed, scientifically correct Saturn rings file we have is Fridger & Grant??s 2k saturnrings png file.
- rthorvald

"Grant's & Fridger's" is more appropriate in case of the Saturn rings. Anyhow is was a very instructive project...

Bye Fridger

[chris]

I really need to improve Celestia's ring rendering. This sequence of images from Cassini shows distinctly different appearances when the rings are viewed from the illuminated and dark sides:

http://www.planetary.org/blog/article/00000842/

--Chris

[t00fri]

I really need to improve Celestia's ring rendering. This sequence of images from Cassini shows distinctly different appearances when the rings are viewed from the illuminated and dark sides:

http://www.planetary.org/blog/article/00000842/

--Chris

But this difference is precisely related to the (separately) required albedo AND transparency inputs. The latter we previously gathered from earthbound observation of a star passage across the rings. The transparency data go into the ring's alpha channel, of course.

I don't think the /rendering/ itself is basically lacking too much. The above cassini ring data now give BOTH info about the albedo (top view) AND transparency (view from below) . That's about all.

Bye Fridger

[chris]

I really need to improve Celestia's ring rendering. This sequence of images from Cassini shows distinctly different appearances when the rings are viewed from the illuminated and dark sides:

http://www.planetary.org/blog/article/00000842/

--Chris

But this difference is precisely related to the (separately) required albedo AND transparency inputs. The latter we previously gathered from earthbound observation of a star passage across the rings. The transparency data go into the ring's alpha channel, of course.

I don't think the /rendering/ itself is basically lacking too much. The above cassini ring data now give BOTH info about the albedo (top view) AND transparency (view from below) . That's about all.

But notice in the animation how different the rings appear from the sun-facing and opposing sides. Then observe in Celestia that there's no difference at all. Celestia isn't taking into account occlusion of sunlight by the denser portions of the rings. When the sun is on the opposite side of the rings than the viewer, I believe that the rings should be darkened by a factor equal to the opacity. That's an approximation that still doesn't account for scattering, but I believe it would produce more accurate renderings of the rings.

There's a paper by Jim Blinn that describes the technique he used to produce an animation of the Voyager flyby. It was written over 20 years ago, but is likely still relevant.

--Chris

[t00fri]

I really need to improve Celestia's ring rendering. This sequence of images from Cassini shows distinctly different appearances when the rings are viewed from the illuminated and dark sides:

http://www.planetary.org/blog/article/00000842/

--Chris

But this difference is precisely related to the (separately) required albedo AND transparency inputs. The latter we previously gathered from earthbound observation of a star passage across the rings. The transparency data go into the ring's alpha channel, of course.

I don't think the /rendering/ itself is basically lacking too much. The above cassini ring data now give BOTH info about the albedo (top view) AND transparency (view from below) . That's about all.

But notice in the animation how different the rings appear from the sun-facing and opposing sides. Then observe in Celestia that there's no difference at all. Celestia isn't taking into account occlusion of sunlight by the denser portions of the rings. When the sun is on the opposite side of the rings than the viewer, I believe that the rings should be darkened by a factor equal to the opacity. That's an approximation that still doesn't account for scattering, but I believe it would produce more accurate renderings of the rings.

There's a paper by Jim Blinn that describes the technique he used to produce an animation of the Voyager flyby. It was written over 20 years ago, but is likely still relevant.

--Chris

After checking Cassini's ring crossing on January 17/18 2007 explicitly in Celestia, I tend to agree. The effect is by far not strong enough right now.

Bye Fridger