Celestia Forums

Hi! With arrival of the equinox in Saturn, Cassini has photographed a number of shadows cast by satellites on the rings, someting never before seen. I have tried to reproduce these in Celestia, but couldn't. Is it possible?

Regards,

Guillermo

It can't be done in Celestia. I don't suppose there's ever been a real need for it, because like you mentioned, moons casting their shadows on the rings has never before been seen.

Um Hungry4info, what do you mean by "can't"? I'm fairly sure that it could be, and I think the request likely lines up with some of the thinking Chris has been putting into a more uniform lighting model though I'm unsure there. Hopefully one of the more involved developers can chime in.

Shadows of moons on rings is in fact something that I've looked at adding to Celestia. But, as with so many things, I haven't had the time to try implementing anything. A higher priority is to make ring systems look better when viewed from the unlit side--the lit and unlit sides should look significantly different, but Celestia doesn't show this yet. After that's working, I may have a go at moon shadows. There may be some numerical precision issues that prevent shadows for very small moons from appearing, but we'll see.

--Chris

Hungry4info wrote:I don't suppose there's ever been a real need for it, because like you mentioned, moons casting their shadows on the rings has never before been seen.

Never before seen by us, yet they actually cast their shadows on the rings on each Saturnian equinox, every 15 years. Press "L" a few times and you have such equinoxes every few seconds.

Many things rendered in Celestia have not been seen for most human history, and many more will not ever be seen, such as our Sun from Alpha Centauri as part of Cassiopeia. At least not for a long time. Yet Celestia renders them as they are. Why not the satellite shadows? Are you loosing your "hunger"?

My question was candid: perhaps they do cast shadows, and I simply didn't find the right geometrical configuration. If they don't, I'm sure Chris will program it into Celestia eventually. Edit: Thanks, Chris. My post crossed with yours.

G

Kolano wrote:Um Hungry4info, what do you mean by "can't"?

With the current build, Celestia is unable to render satellite shadows onto rings.

abramson wrote:Never before seen by us, yet they actually cast their shadows on the rings on each Saturnian equinox, every 15 years.

Lol yes, I'm quite aware of this, as such I wrote "seen", as opposed to "occurred". The previous Saturnian equinox predates the existence of Celestia though, so, there has never been a real pressing need to implement it. I'm sure once we see Titan's shadow swooping across the rings, the want for such implementation will increase.

abramson wrote:Many things rendered in Celestia have not been seen for most human history, and many more will not ever be seen, such as our Sun from Alpha Centauri as part of Cassiopeia. At least not for a long time.

Oh no doubt. Being ability to see Sol from Alf Cen isn't hard to do though, there's no special graphical implementation that needs to be done. Celestia, being a 3d simulation of the universe, would have no problem showing me where in the sky Tau Ceti is from Sirius, or where Epsilon Eridani would be from Proxima. However the rendering of satellite shadows onto the rings would require additional rendering beyond that which has already been coded.
I'm certainly all for satellite shadows onto the rings. I'm just saying I fully understand why they haven't been implemented yet. Similarly, rings don't cast shadows onto moons, and I don't think there's much of a pressing need for that now, because it's never been observed (yes, I realise it has occurred before).

If Chris didn't want to render this for a while, I couldn't blame him.