Testing applications are now available for Linux now that a major timing bug issue has been taken care of. Windows applications are also updated in the windows thread. Mac applications have been forwarded to the appropriate team members for compilation/testing and should be available soon.

Please feel free to leave suggestions/comments here and bug reports in this thread.

The demo is computationally expensive and will not run sufficiently fast on some machines (runs a bit choppy on a Pentium I5 2.4ghz CPU). The "cube_test" application has a much faster demo that uses the same graphics engine. If either works, the final screensaver should run smoothly on the same machine. The final screensaver will have precalculated paths and images, taking care of the speed issue.

mwdemo_linux.tar.gz (v2)

cube_test_linux.tar.gz (v2)

To use the application, download it and extract it to a folder on the desktop or in another folder if you prefer. Then run either of the two executable files that are extracted. As a precaution, it may be a good idea to save any data in other applications before running the full-screen version. For those that do not have Windows XP or later, a zip utility such as 7-zip or WinZip can be used to open the file. The controls listed below are similar to those of Celestia with a few more added in.

Source for all files can be found here.


CONTROLS

ESC - Exit application
Tab : Start over
Shift-Tab : save new start-point
Alt-tab : leave application temporarily when in full-screen mode
Prtsc or Print-screen: saves a screenshot

MOVEMENT

< / > : accelerate backwards /forwards
F1-F9 : change acceleration (each step is 10 times faster than the previous)

Arrow : look around
Ctrl-arrow : rotate view
Shift-arrow : revolve camera around galaxy center (inverted)
Alt-arrow : accelerate up/down/left/right
Spacebar : stop motion

Backspace : focus on center of galaxy
Shift-backspace : focus on Sol

Enter : travel to center of galaxy
Shift-enter : travel to Sol (gives an Earth view of the wedge)


APPEARANCE

1 / 2 / 3 : select object 1-3 (wedge, stream, galaxy)

+ / - : increase/decrease luminosity of object
Shift- + / - : increase/decrease star blur radius
Alt- + / - : increase, decrease number of stars visible

A : toggle axes view
C : toggle camera view


Notes:

If the application runs a little choppy, then it may help to hold keys a little longer if they do not activate every time, esp 1 / 2 / 3 when choosing an object.

(Alt-minus) and (Shift-minus) will quickly increase the frame-rate since they require fewer screen-writes.

As you move away from the stars, they will combine and brighten. The brightness can be reduced manually (see above).

Update: fixed broken links

Update: added replacement keys for foreign keyboards:
p and m keys replace + / -
b and f keys replace < / >

woa, can't wait for the Mac version!

by the way, how far are we on calculating the milkyway in percentage?

The immediate galaxy is mostly mapped if you only consider relative angles to the Earth. The part hiding behind the central halo is much more difficult to map because the star density is greater there. The distances of the stars are harder to find and mapping them is an ongoing process.

Countries including the US, UK and now China have all had plans for telescopes that are specifically designed for this task. I believe the most complete catalog of star distances is currently Tycho2 which maps 2.5 million stars out of the estimated 300 billion stars in the Milky Way.

MilkWay@Home uses data from the Sloan Digital Sky Survey to narrow in on the structure and evolution of streams in the galaxy. The SDSS maps galaxies and other very distant objects making it possible to map approximate positions of F stars in the Milky Way thousands of times more distant than those in Tycho2. The SDSS has currently mapped more than 6% of the sky (http://www.sdss.org/news/releases/20031028.powerspectrum.html).

ESA's GAIA will map ~100 million stars, right? Still a long way off from all of them (and I doubt they'll all be part of the milky way), but..

"ESA's GAIA will map ~100 million stars, right? Still a long way off from all of them (and I doubt they'll all be part of the milky way), but.."
-Emanuel

My original numbers were misinformed. Currently the largest catalogs I know of have roughly 1 billion relative star coordinates. NOMAD is one example. Also the Tycho II catalog does not contain parallax data which will be available in many upcoming catalogs such as the one you mentioned. The current estimates for the distances of Tycho II stars are not accurate enough to show decent distributions of star density when all of the stars are mapped. The Hipparcos catalog (released in 1997) does contain parallax data of 100,000 stars which allow accurate 3-dimensional coordinates of stars to be mapped.

For those that are interested, here is a simulation showing Tycho II estimations of 2 million stars made by "granthutchison" as a Celestia add-on. The original data can be found here.

showstars_win.zip

Instructions for use are found in the zip file. Star colors were not included in this version.

This is a great start, Shane.

At some point--when you're done, I hope someone can help you convert the SDL graphics calls to OpenGL. That will quadruple the framerate and lower CPU usage for the screensaver app.

I have looked into this a bit myself. I am looking forward to testing an OpenGL implementation particularly on my lower end machines.

I have done some in-depth research into using OpenGL for the star-sprites. It seems that a 4x speed-up is a conservative estimate at least on my newest machine. The resulting speed-up could be closer to 10 or 15 times the single-threaded CPU-driven algorithm.

By using "glBlendFunc(GL_SRC_ALPHA, GL_ONE);" I am able to create additive blending without the use of get and put pixel.

Once the new implementation is complete, I will see if it is possible to create a moving screensaver view. At the very least, I should be able to pan images across the screen for a more dynamic effect instead of relying on a slideshow effect.

Update: The speed boost is most apparent for larger blurs. The demo as-is uses blurs that are only a few pixels in diameter so there is, unfortunately, no speed-up currently for the screensaver under OpenGL. It actually runs a few percent slower than my current implementation. There may be a way to do a hybrid approach that will combine the benefits of both approaches, but it does not seem likely since the bottleneck seems to be the transmission of data between the graphics card and the CPU (there are 50,000 blurs drawn per frame). This issue might theoretically be overcome by programming the graphics card directly.

The new implementation does, on the other hand, use substantially less memory, requires less code complexity, shows finer detail with greater color depth, and scales nicely for larger blurs, showing only modest degradation in speed as blur size increases significantly.