Stellar atmosphres

[chris]

This is precisely why I am not moving forward on any new builds past 1.5 pre2 until this problem is solved.

I always thought if something?€™s works well than leave it alone. Chris tried to upgrade things, but it turned out to bring in other major problems, mainly moons looking like little stars, which I hate, so until he can solve the problem for a future build he should put things back the way they were if at all possible. At this point I am willing to live with the halo effect on the moons, for now, but I will not do any further upgrades until this is fixed to everyone?€™s satisfaction.

The halos around moons and planets are not in 1.5.0pre3.

It?€™s also a shame that so many add-ons seem to be impacted negatively with the code changes at this point. These newer builds are starting to feel like a totally different and new version of Celestia, with a very different look and feel. I even noticed recently that the time settings has been changed so that there no longer has a small box pop up to advance the time by months in a quick click. Now you have to highlight the section of the date you want and advance it with the arrow keys. I liked the old way better although it did look tacked on sort of.

Oh well we will just have to wait and see.

I've tried to maintain compatibility with old add-ons as much as possible, but there were inaccuracies in Celestia that absolutely needed to be corrected, such as the use of single precision for rotation properties. The time setting dialog was changed because the standard Windows time dialog wouldn't allow setting the time to a year before 1752.

--Chris

[fsgregs]

Chris:

Your last post did not comment on star halos. PLEASE PLEASE add back halos, or give us the option to add them back as a CFG command.

This ...



is just not a "star". It is a big white circle in space.

THIS



is a star!!! (at least in my opinion)

I know we can get around this by creating invisible planets around every star we might want to visit, and creating atmospheres ... but that should not be necessary. Really ... the star code is just ... well ... wrong!

PLEASE --- give us halos again.

Frank

[buggs_moran]

Or at least the option to turn them on and off either in a menu or through the stc...

[bdm]

I have commented on the configuration of star halos, and I'll expand on my earlier remarks:

1. The display of Star halos is linked to the display of atmospheres in 1.4.1. It should NOT work like this. They should have a separate configuration option.

2. This configuration option should turn them all on or turn them all off.

3. IMO the Halos in 1.4.1 do not look right. They are too narrow and too bright to be a corona. They would look much more like a corona if they were fainter and extended out from the star more. They are also of uniform thickness all around the star. That is unrealistic because the sun's corona tends to be wider at the equator and narrower at the poles.

4. Halos should be configurable in the STC file.
Corona
{
Color [1.0 1.0 1.0] # Usual colour values
Transparency 0.95 # Transparency at star surface. 0 = opaque, 1 = transparent
Radius 2.5 #Distance at which it fades to transparent. Units are multiples of stellar equatorial radius, which permits more uniform settings to be defined for all stars
Oblateness 0.3
}

We could add other features as well such as meshes and the like.

5. The default behaviour of coronas should go in the CFG file.

[dirkpitt]

At close distances from the sun (e.g., < 4 million km), I think it becomes irrelevant whether you can distinguish a corona or not -- any sensor, including the human eye, will probably be completely blinded, i.e., to be physically realistic, the whole screen should saturate to white at close stellar distances. Whether people actually want this behaviour is another matter..

[Don. Edwards]

One other thing I would like to have have as a selectable item is the star flares of old. I know they may not be realistic but I liked the one I used and I miss it not being there. In certain instances it lends a little realism when you take a sceen capture and are trying to show things off. Just me but I would like the option to have them back and at the distance they used to be, not only when you were far away from the star.

Just another 2 cents.

Don. Edwards

[jwmickelson]

Perhaps another way of tackling the problem would be to better define what should (realistically and artistically) be seen surrounding celestial objects like stars in a simulation like Celestia. I think it's obvious that a star's "atmosphere" is a completely different beast than a planetary atmosphere. The past method of rendering them using similar code to the atmosphere of planets was probably a simple way of expanding the the feature set to represent what we expect to see.

The comments in this thread outlining characteristics of the solar atmosphere are great, because it gets us thinking about how this should be done in the future. Even if atmosphere's of old are turned back on, as some are requesting, I still think it's not addressing the total picture.

Stars are emissive and dynamic objects, and our proximity to one fairly mainstream star probably gives us a limited picture of stellar characteristics across the entire stellar population.

So in the spirit of furthering this discussion here are some things that I think could be be addressed in future stellar rendering mechanics:


- Corona Rendering (perhaps with texture to provide irregularities)
- Chromosphere rendering (perhaps with texture to provide irregularities)
- Research into dynamic stellar atmospheres by mass and radius (for both high/intermediate/low mass stars and the affects on ratios of Corona and Chromospheres etc..)
- Procedural Flares
- Procedural Sunspots
- Procedural Granulation (ok I know I'm dreaming)
- Jets
- Accretion disks

Obviously this is a lot of rendering, and like any "idealistic system" should scale perfectly so that some would only be performed at close enough distances

Again, the reality vs. artistic camps will have to duke this out, but it would seem that stellar atmospheres is a much bigger question than just turning halo's back on... even if I want them back myself.

Thanks to Chris and everyone's great work building and testing the pre release for the rest of us lamers.

Jonathan