Project Orbiter Galaxy

Bloodworth

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You may consider talking to the developer of "Infinity-the quest for earth" at http://www.fl-tw.com . He is working on a procedural generation engine for a realistic galaxy size (i.e. 2 - 300 billion stars). He even has a early rendering video of it on youtube which can be accessed from the front page of the site.
 

jedidia

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I think that's a bit out of my league... I have a rather simple model in mind, chunking the galaxy up into 10^3 parsec cubes, the star density of which will be determined by their position in the galaxy (probably going to use a grayscale image as reference). So, while you can scroll through the cubes seamlessly, you won't be able to zoom out too far. A 2-d image of the galaxy will be provided where you can place markers referencing to certain cubes for faster navigation, but a completely zoomable galaxy is just too much for me. This is actually the first serious application with 3d graphics I'm doing ever, so it won't be high-tech.

Plus, I have not even started with procedural generation yet. I'm still experimenting with filing and loading predefined stars to keep a) high efficency and b) high modability (i.e. that it will be easy for a modder to include his custom generated star system).
 

jedidia

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I'm making slow progress here, enough to notice that my galactic position of Sol in the z axis simply can't be right. Because in z minus the catalog seems to stretch on for hundreds of lightyears, while in Z+, Sol is in the las 10 parsec cube containing anything... there's nothing above.

my information says that Sol is about 20 parsec above the plane (that's 65.2 lightyears) and that the disc has a thickness of about 1000 lightyears. So if the plane is it's center, there should still be plenty above sol. So, anybody got more reliable information on the position of our solar system in the galaxy?

Edit:
Great, you search about sol and the galactic plane, and what do you find? 90% Armageddon "we're going to collide with something in 2012" crap... oh well.
Anyways, it turned out that my info about sols position was as reliable as it can currently get, and hunting for the causes of where all those stars went (oh my god, it's full of... not stars!) finally led to the discovery of a bug in the conversion from earth-centered coordinates to galactic core-centered coordinates. Fixed it, and everything is smooth. The constellation now look identical to celestia, so I guess I can finally move on and get to the real work... :)
 
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jedidia

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Oh my god, it's full of stars (finally!):



and it scrolls seamlessly through them! :)

next will be a bit of a user interface, then the generator for filling in the missing few billion stars, and THEN the big stargen overhaul... I'm afraid the last one could take the better part of a half year, especially considering what's comming up in RL at the end of this month...
 

jedidia

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It's comming along, mouseinterface fully working now. Many brave pointers have selflessly flung themselfes into the void until stability was finally achieved.

Now, the missing stars... i.e., galaxy creator. I could use a little help with that one, majorly information about the presumed composition of our galaxy: which spectral classes and sequences apear in what concentration? any info or website with information about assumed stellar density and composition of various places in the galaxy are welcome!
 

tgep

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Spectral type and class are generally a grab bag outside of the class-1 first generation stars outside the galactic core halo. Agood starting point would be to map in the stars from the 88 constelation outlines.

Stary Night pro-6 can help you do this. Celestia also has a database of info you could use. As for plotting the other planetary systems, The extra-solar database should have the info you need. You can also find good data on star clusters in the NGC\IC Catalog.
 

jedidia

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Spectral type and class are generally a grab bag outside of the class-1 first generation stars outside the galactic core halo.

Sorry, I didn't really understand what you are saying here...

Agood starting point would be to map in the stars from the 88 constelation outlines.

Those are allready in, since they are in the Hyparcos catalogue, which is included in the HYG-database.

As for plotting the other planetary systems,

The system generator will come later. Currently it's only about generating stars, so that they apear in reasonable amounts and classes.

thanks for your help, anyways :cheers:
 

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The central bulge of our galaxy is populated by mostly 1st generation stars. Most of the stars in the spiral arms are a mix of pop.1 and newer stars formed from prior super novae.
 

Bloodworth

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As much as I and people of like mind are chomping at the bit for this, I agree with TGEP; this will be well worth the wait.
 

jedidia

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Looks like I'll have to read up on stellar evolution again. Don't know enough about it, I noticed.

Anyways, yesterday I found some stuff about star-density at the core. It said close to the core, estimates go up to 100,000 stars per single cubic-parsec. Since I'm loading it all in 1000 parsec^3 (10*10*10) cubes, this will be WAAAAAY too much to handle. Plus, the planetary systems would become a mess anyways, I don't think there could even be consistant planetary systems in such a set-up. So the core won't look too realistic. I don't think that my current setup is able to handle much more than a 1000 stars per 10-parsec cube (since there are 27 cubes on display at any time... 3*3*3 cubes, with the focus being on the center one, and the sourrounding ones being deleted and recreated while scrolling). Well, the engine could take it, but the CPU won't (and mine isn't too slow).

On the up-side, I decided to put in the currently known positions of globular clusters in the halo, creating the stars in them by the generator. Anyone got a library with the positions of the globular clusters?

Note on RL: my room gets emptier and emptier, all stuff packed up nicely in boxes. Me and my wife will move to bosnia this fryday, so it could well happen that I'm going offline for a few days.
 

tgep

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The NGC\IC 2000 catalog will provide all the data you could possibly want. Just look for the globular clusters.

Other good referances are:
SkyAtlas 2000 Companion ~ Robert A. Strong
Cambridge Star Atlas ~ 3rd edition ~ Will Tirion ~ Cambridge Press

Recomended reading on Stellar evolution:
Exploration of the universe ~ Abell, Wolfe, Morrison ~ 6th edition ~ Saunders College Publishing ~ Chapters 21-30 inclusive.
 
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jedidia

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W00T, I finally got internet access again. But I'm also very busy now, so progress has been slow, but I'm still at it.

I now have a working 2d map of the galaxy as a kind of oversight map that is scrollable, zoomable and all, now I'm taking on the actual generation code for stellar clusters. This shouldn't be too tough, but the solar system generator that comes after that will be a pain in the ass. I don't think I'll have a working version handy before spring...
 

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I'm working on the generation routines currently, and I'd need some bits of information on the fractional occurence of classes and sizes. I.E. what's the assumed composition of the galaxy? how many percent of the stars are O-class, B-class and so on?

Also, there's a thing about the size I don't quite get. For one, size is depending on the sequence (a middle-massed star will blow up when it leaves its main sequence, and later collapse again), but also on mass. As I understand it, a very massive star can be a giant and still be in its main sequence. Also a class K star will transfer it's spectrum towards M when it leaves main sequence and blows up to a giant, so I guess there should be more Red Giants than any other giants, but there are also class O giants (probably in their main sequence). How frequent are such stars? Anybody got any links to an in-debt article about the topic?
 

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Interesting project :thumbup: i´m sure that it worth the wait.

Now with 400 exoplanets discovered it could be a must have for orbiter
 

tgep

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Since Mass and temp are the main determining factors of a stars stage of evolution at any givin point in time, I would use a sliding scale for evolution based on temp for O, B, A, and F class stars based off of the H~R Diagram.

Since the best you will get is an estimate of general percentages based on actual obsevations, you won't be too far off the mark, you'll maintane the realism factor, and save yourself a lot of reading to come to the same conclusion.
 

jedidia

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Now with 400 exoplanets discovered it could be a must have for orbiter
Unfortunately, all I can provide is a relatively accurate starmap, with randomly generated systems. Mapping in pre-definded systems with known exoplanets will be the job of other add-on developers (I have a plugin system in mind that should allow adding pre-defined systems by simply dropping them into the right directory...)

Since Mass and temp are the main determining factors of a stars stage of evolution at any givin point in time, I would use a sliding scale for evolution based on temp for O, B, A, and F class stars based off of the H~R Diagram.
Thanks, I'll do that. I assume you mean the Hertzsprung Russel Diagram?

Random star-generator is working so far, but isn't accurate yet. Produces decent starclusters, but I think their composition won't live up to an examination by someone who knows his physics. Plus, I realized that the rand()-function of C++ won't get me anywhere... since it has a maximum range of 32767. That would be a terribly repetitive galaxy. Anyone got any recommendations on a good random numbers generator with a range of a few hundred billions?

---------- Post added 11-04-2009 at 11:25 AM ---------- Previous post was 11-03-2009 at 02:31 PM ----------

I can't seem to find any data on the assumed fractional occurance of stars of different masses. Currently I go with the following chances at creation:

2% chance for a supermassive star to be created, 20 to 90 SM
8% for a pretty massive star, 10 to 20 SM
10% for a massive star, 3 to 10 SM
40% for a medium mass star, 0.5 to 3 SM
20% for a low mass star, 0.08 to 0.5 SM

these numbers are just out of my gut and without any basis on anything else. Maybe someone more familiar with the matter could correct this a little?
 
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I'm probably just being dense here. Can you clarify: is this going to be an MFD that simply displays the stars in our solar system's vicinity? Or is this going to include some sort of mechanism by which we can actually travel to those stars? If so, how do you envision it working? I'm confused :) (which is easily done I might add!)
 
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