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Shane Reilly
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Message 41203 - Posted: 2 Aug 2010, 21:24:54 UTC
Last modified: 2 Apr 2011, 6:18:37 UTC



This thread will be continually updated with the screensaver progress in its final stages. Here is the latest screenshot of the wedge and galaxy backdrop with the current Sagittarius stream estimate provided by David R. Law et al. Adding color uses considerably more memory for pre-drawn frames along with a decrease in speed, so at this time, a trade-off would have to be made between having real-time motion and having color given that only a small portion of the CPU is dedicated to graphics. Color seems to be the popular choice so far, but additional votes are welcome.

Click here for a full size image.

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Message 41206 - Posted: 3 Aug 2010, 4:02:15 UTC - in response to Message 41203.

Sweet!

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Message 41209 - Posted: 3 Aug 2010, 5:45:54 UTC

You never did say if GPU crunchers can use this screensaver in the other thread..

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Message 41210 - Posted: 3 Aug 2010, 6:28:36 UTC - in response to Message 41209.
Last modified: 3 Aug 2010, 6:49:34 UTC

The explanation given for GPU interaction could have seemed a bit cryptic in retrospect. In short, yes, any application, whether it interacts with the GPU or not will function, albeit a little more slowly while MilkyWay@Home is crunching on a double precision floating point GPU. The screensaver does not rely on GPU's so it should have no effect for or against the screensaver.

There are nearly a dozen applications which will be integrated with this screensaver, including ATI, NVIDIA and CPU versions for Mac, Windows, and Unix-based operating systems. I plan to release CPU versions first, NVIDIA shortly after. The ATI version will take a bit longer as it is currently under major redevelopment and I have to wait for it to be completed by those working on it.

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Message 41211 - Posted: 3 Aug 2010, 7:33:13 UTC

awwww, i just got a new iMac with a ATI card.. and now i have to wait longer. :(
by the way, my vote is on colour! Is the yellow bit the part that we crunched?

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Message 41212 - Posted: 3 Aug 2010, 8:12:07 UTC

Great work Shane:

I tend not to use screen savers myself, but I appreciate the effort you are putting into this project.

Question: I run up to four GPU's at a time, so how would this affect the screen saver, if at all?

Kind Regards
David
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Message 41219 - Posted: 3 Aug 2010, 11:31:34 UTC

Really looks nice! Great job!

Alexander

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Message 41220 - Posted: 3 Aug 2010, 12:00:44 UTC - in response to Message 41203.

[quote]Color seems to be the popular choice so far, but additional votes are welcome.
quote]

No change, still voting for color!

Or would you like to eat a black and white steak, chicken or salad? And how do you think about a grey bear?
I spend some FLOPS for a nice background!

Alexander

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Message 41221 - Posted: 3 Aug 2010, 13:41:06 UTC

Hi David, Hi everyone here! Despite a less amount of CPU job during screensaver mode, I think a nice and colorful one would be a good promo for the project: you know, many BOINC users choose projects depending on a brilliant graphic or not. I think you can try to develop a screensaver nice for the eyes and not so "vampiric" for the CPUs: the main result for the project as credits growth will tell if we're right!
In my humble idea, of course ;-)

Greetings!

The Dreamer

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Message 41222 - Posted: 3 Aug 2010, 13:54:17 UTC - in response to Message 41221.

Hi Dreamer

I agree with you, color is important.

Cheers
David
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Message 41223 - Posted: 3 Aug 2010, 14:12:18 UTC

Another vote for color!
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Message 41225 - Posted: 3 Aug 2010, 14:52:38 UTC - in response to Message 41211.
Last modified: 4 Aug 2010, 2:05:23 UTC

Is the yellow bit the part that we crunched?

-Koen Visser

Yes, the SDSS wedge spanning out from Earth is used to determine the best fit for the Sagittarius Stream. The wedges are displayed in yellow because only the F-stars are shown. F-stars have the least error when calculating star position. The bright spot on the wedge indicates where the stream (shown in blue) intersects it although the precise position and shape of the stream is the problem that is being solved (the stream shown is one of many estimations). A different wedge is calculated every month or so and the compilation of the results is ongoing (as is the SDSS survey).

I've modified the demo image for this thread to include a more accurate model of the Milky Way by changing the original ESO image that the Milky Way stars are sampled from. Seeing the change may require refreshing the browser (ctrl or apple-R) for those who are viewing it a second time.

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Message 41246 - Posted: 3 Aug 2010, 23:54:13 UTC - in response to Message 41212.
Last modified: 4 Aug 2010, 0:49:55 UTC

I run up to four GPU's at a time, so how would this affect the screen saver, if at all?

-David Glogau*

It shouldn't effect the screensaver adversely at all. I was told by the person that wrote the NVIDIA GPU code that the GPU applications free up the CPU by about 90% although 4 GPU's I imagine might use about 50% of the CPU at idle. If the screensaver were able to tap this resource it would change matters altogether. In retrospect, having a double precision GPU might be advantageous if one were to assume that the BOINC automated graphics pinching function is able to see this opportunity and allow the screensaver more CPU time as a result. I will look into it.

It is also worth mentioning that the team is using the currently crunched data to form an N-Body simulation to representing the findings so far. The N-body simulation will also use distributed computing to calculate stream motions and will be run alongside the "separation" application. We appreciate all your help! The N-body project should be done in the next few months and it will have a screensaver of its own using the same screensaver infrastructure.

I should have a demo at least for Windows up by tomorrow. The Linux and Mac ports will be up shortly after. If things go well, I will begin releasing the modified main applications.

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Message 41251 - Posted: 4 Aug 2010, 2:08:40 UTC

The color looks much better the black and white. It helps to visualize the pictures better. I think the Milkyway could be toned down just a tad so it doesn't look as bright.
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Message 41253 - Posted: 4 Aug 2010, 2:52:59 UTC - in response to Message 41251.
Last modified: 2 Apr 2011, 5:52:31 UTC

The color looks much better the black and white. It helps to visualize the pictures better. I think the Milkyway could be toned down just a tad so it doesn't look as bright.

-banditwolf

The brightness is touchy. I like to create a little over-brightness in the blue to maximize the contrast, but the tiniest amount over and resolution is lost since the Milky Way is relatively small compared to the wedge. On top of this, the effect of multiplying intensity changes over the thousands of stars used to draw the Milky Way leads to a relatively large difference resulting from a change of even 1 unit intensity per star. This problem could be overcome by a number of techniques, but I will try to solve by adjusting the view distance to simplify things for now. This should be a little better (changing the thread image as well). Original image here.




The demo that will be released allows interaction through the keyboard and screenshots (Prnt Scrn key on PC), so anyone that would like to can submit enhancement ideas. I look forward to seeing them!

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Message 41268 - Posted: 4 Aug 2010, 15:38:46 UTC - in response to Message 41253.
Last modified: 4 Aug 2010, 15:41:00 UTC

Wow, it's so pretty - I don't suppose you could also release a dedicated standalone version? XD
Edit: oh, or do you already intend to? I should have read your last post more carefully.

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Message 41272 - Posted: 4 Aug 2010, 18:15:52 UTC

Colour.

That is amazing, and I agree, it will likely add interested users just because you have an interesting "eye-candy" screen saver which more or less shows what milkyway is doing (in a pictorial sense - pictures are worth 1000 words).

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Message 41280 - Posted: 5 Aug 2010, 2:08:16 UTC

Yes, yes, yes, yes, yes. I am so glad to be living in these days when I can be part of something like this. Even if what I am adding to the whole is not significant right now, just being part of it is wonderful. I really dig where your are going with the screensaver. I vote for color.

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Message 41298 - Posted: 6 Aug 2010, 10:46:49 UTC
Last modified: 6 Aug 2010, 11:16:06 UTC

The coloured version looks very nice!

One idea to speed up the screensaver:
It seems you try to display a lot of points (stars). I guess many of them will be verry close (at lest on the screen). Would it be possible to reduce the data to display by some kind of "abstraction" ? Maybe you can select only some representatives of the whole star dataset, based on distances to each other. Another idea would be to "merge" several stars together, and replace them by one star with an "averaged" position and brightness. What do you think?

About the ATI GPU version: I have a relatively fast ATI Mobile HD 5850 in my new laptop,
but it does not support double precision. Will there be a GPU app for single precision GPUs some day ??

Best regards,
Frank

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Message 41299 - Posted: 6 Aug 2010, 11:11:19 UTC
Last modified: 6 Aug 2010, 11:13:53 UTC

Another idea to optimize the sceensaver:

Which part will be changed more often, the Milky Way, or the wedge?
The wedge on the preview screenshot basicially looks like a slice moving in 3D. Maybe you could use a 2D surface to render the wedge into, and then let OpenGL project the data onto the "slice" in 3D?
If the Milky Way will not change, you might get some speed back by "preparing" the data once, instead of colouring and transforming it for every screen update.

best regards,
Frank.

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