The Galactic Core

[Chuft-Captain]

OK thanks,

To be honest, I'm more interested in whether you've made any progress on the depth-sorting issues that I PM'd you about a while ago. (This little core stars project was just something I started playing around with because the other project's stalled due to the DS issues).

Any progress to report on the depth-sorting??

Regards
CC

[chris]

CC,

Playing with various of Celestia's parameters isn't going to do you any good. You're wasting your time. They'll change the symptoms slightly, but that's all. You cannot get around the underlying distance design problem until Chris has eliminated it. Although he has a conceptual framework for a solution, it won't be implemented soon.

Actually, I've got distant stars working on my system right now. After making a few renderer changes, I was able to place a star 500,000 ly from the Sun and view it without any jittering. There's a limitation however: star positions are still single precision, so at extreme distances, star placement is rather coarse. Star positions are effectively limited to about 0.1 arcsecond precision; at extreme distances, this translates to a very big interval. With further work, this limitation can also be overcome, but the current patch is huge improvement. It should be adequate for any observer star.

--Chris

[Reiko]

CC,

Playing with various of Celestia's parameters isn't going to do you any good. You're wasting your time. They'll change the symptoms slightly, but that's all. You cannot get around the underlying distance design problem until Chris has eliminated it. Although he has a conceptual framework for a solution, it won't be implemented soon.

Actually, I've got distant stars working on my system right now. After making a few renderer changes, I was able to place a star 500,000 ly from the Sun and view it without any jittering. There's a limitation however: star positions are still single precision, so at extreme distances, star placement is rather coarse. Star positions are effectively limited to about 0.1 arcsecond precision; at extreme distances, this translates to a very big interval. With further work, this limitation can also be overcome, but the current patch is huge improvement. It should be adequate for any observer star.

--Chris

ETA on this patch?

[Chuft-Captain]

Actually, I've got distant stars working on my system right now. After making a few renderer changes, I was able to place a star 500,000 ly from the Sun and view it without any jittering. There's a limitation however: star positions are still single precision, so at extreme distances, star placement is rather coarse. Star positions are effectively limited to about 0.1 arcsecond precision; at extreme distances, this translates to a very big interval. With further work, this limitation can also be overcome, but the current patch is huge improvement. It should be adequate for any observer star.

That's good news, especially as I believe in the context of my CORE addon, the only object which will suffer the positioning inacuracies will be the Barycenter. (As all the other stars are placed with reference to this Barycenter, their orbits should be able to be described within single precision limits).

There were 2 other minor issues (with the core stars) which I forgot to mention which you may like to test out with your new code:
1. Cannot click on these stars to select them. (They seem to be un-selectable). However, they can of course be selected by name in the ENTER menu.
2. Their orbits do not display when star-orbits are enabled (However, their labels do display)

[chris]

CC,

Playing with various of Celestia's parameters isn't going to do you any good. You're wasting your time. They'll change the symptoms slightly, but that's all. You cannot get around the underlying distance design problem until Chris has eliminated it. Although he has a conceptual framework for a solution, it won't be implemented soon.

Actually, I've got distant stars working on my system right now. After making a few renderer changes, I was able to place a star 500,000 ly from the Sun and view it without any jittering. There's a limitation however: star positions are still single precision, so at extreme distances, star placement is rather coarse. Star positions are effectively limited to about 0.1 arcsecond precision; at extreme distances, this translates to a very big interval. With further work, this limitation can also be overcome, but the current patch is huge improvement. It should be adequate for any observer star.

--Chris

ETA on this patch?

I'll estimate 3-4 days, but it really depends on whether any issues show up during testing.

--Chris

[chris]

There were 2 other minor issues I forgot to mention which you may like to test out with your new code:
1. Cannot click on these stars to select them. (They seem to be un-selectable)
2. Their orbits do not display when star-orbits are enabled (However, their labels do display)

None of this is surprising--stars further than 16k light years from the Sun simply aren't supported in the current version of Celestia.

--Chris

[Chuft-Captain]

There were 2 other minor issues I forgot to mention which you may like to test out with your new code:
1. Cannot click on these stars to select them. (They seem to be un-selectable)
2. Their orbits do not display when star-orbits are enabled (However, their labels do display)

None of this is surprising--stars further than 16k light years from the Sun simply aren't supported in the current version of Celestia.

--Chris

Here's a picture of the core stars using the recent SVN build from cartrite. This is from approx 19 light years, centered on Sag A (the SMBH). (rendering stars as fuzzy points).


Currently a total of 10,000 stars (~1600 in the central parsec), with the following approximate proportions:

Code: Select all

1.4%   A
17.8%  B
15.7%  F
4.5%   G
0%     K
52.6%  M
14%    O

(No Wolf-Rayets yet)

Any opinions on the proportions?

See here for background info: http://en.wikipedia.org/wiki/Galactic_c ... population


Stars now render from all angles (Thanks Chris ), but they still seem to be un-selectable as above. I don't think it's really a big deal if we can't display the orbits (as it would be a mess of spagetti with this density of stars), but it would be quite good to be able to click on individual stars to select them.

Compare the image above with Larry Niven's fictional description:

"Gone were the obscuring masses of dust and gas. A billion years ago they must have been swept up for fuel by the hungry, crowded stars.
the core lay before me like a great jeweled sphere. I'd expected it to be a gradual thing,....there was nothing gradual about it.....The red stars were the biggest and brightest. I could actually pick some of them out as individuals. The rest was a finger painting in flourescent green and blue....It was all so bright.
I'll show you how bright it was.
Is it night where you are? Step outside and look at the stars. What color are they? Antares may show red, if you're near enough; in the system, so will Mars. Sirius may show blueish. But all the rest are white pinpoints.
Why? Because it's dark. Your day-vision is in color, but at night you see in black-and-white, like a dog.
the core suns were bright enough for color vision."