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Shane Reilly
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Message 41303 - Posted: 6 Aug 2010, 17:40:13 UTC - in response to Message 41268.  
Last modified: 7 Aug 2010, 6:23:03 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?"

-Emanuel

The standalone is used to test and design the screensaver routines very quickly and it is easily made available, so the demo being released could be called the standalone version.

"It seems you try to display a lot of points (stars). I guess many of them will be very 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?

- Frankm

Absolutely! I have been kicking this idea around since the start of the project, but there are a few issues. The stars could be cut up into sections and averaged by using an inverse tree. This is similar to what is done when rendering textures at further distances. This tends to create a flickering effect during the transition that I considered undesirable for the screensaver. It could be overcome completely by waiting until stars were less than an 8th of a pixel apart to use their average. This did not seem necessary for the screensaver as it is now, but this mehthod would be critical for a larger-scale application using millions of stars and a larger range of distances.

"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 ??"

- Frankm

We are working on a way to do that for the N-Body computations. It is too early to say for sure at the moment, but one idea was to split up each double precision value needed into three or four floating point operations. It would be slower than direct float-based math, but potentially useful if it allowed full use of the GPU.

Edit: this idea would actually produce slower results than not using the GPU on closer inspection. Matt A. and Ben have told me that the N-body will rely on double-precision math as well. The screensaver could benefit from using single precision enhancements, but this would most likely be implemented in later versions.

"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?"

-Frankm

That is clever. I hadn't thought of it. It would produce flattening and make the wedge invisible from certain angles, but other angles could potentially get a boost in speed. The library already uses textures for the individual stars so it is hard to say how much faster it would be without testing. Open-GL might be able to accelerate the current star draws as well, but CPU code was chosen for maximum compatibility in this revision and also because there does not seem to be native GPU support for pixel-summing with textures. This might require GPU programming.
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Matt Arsenault
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Message 41304 - Posted: 6 Aug 2010, 20:32:58 UTC - in response to Message 41298.  


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 ??


I think that card should support doubles. Nearly all of the 5xxx series do, except randomly a couple don't.
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Message 41310 - Posted: 7 Aug 2010, 3:57:40 UTC

I have a question that didn't hit me till now..

Most screensavers for BOINC projects only keep showing till the current WU is finished ..then the screensaver goes away when the new WU starts crunching..what will happen if a GPU user opens up the screensaver being that it only takes me about 1:14mins to complete 1 WU?
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Shane Reilly
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Message 41311 - Posted: 7 Aug 2010, 4:44:27 UTC - in response to Message 41310.  
Last modified: 7 Aug 2010, 6:24:24 UTC

Most screensavers for BOINC projects only keep showing till the current WU is finished ..then the screensaver goes away when the new WU starts crunching..what will happen if a GPU user opens up the screensaver being that it only takes me about 1:14mins to complete 1 WU?

-ztmike

That's interesting. BOINC controls screensaver activation and resource use. It may automatically terminate a screensaver under certain circumstances. If it does terminate the screensaver early, it is something I could discuss it with the BOINC team since it would be highly undesirable. I would consider it a bug. Please feel free to let me know if this happens after the initial release.
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Message 41328 - Posted: 8 Aug 2010, 16:28:36 UTC - in response to Message 41303.  
Last modified: 8 Aug 2010, 16:32:55 UTC

Maybe it would help to look at the "abstraction" problem from the astrophysics point of view? You could merge stars based on their distance and mass/brightness once, and then use this abstracted dataset for the screensaver. If you are already looking at N-Body simulations, you could possibly re-use a spatial tree representation (like a barnes-hutt octtree); the end nodes of such a tree could be candidates for merging. Would it be possible to allow the user to control the amount of abstraction?

best regards,
Frank


"It seems you try to display a lot of points (stars). I guess many of them will be very 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?"
- Frankm

Absolutely! I have been kicking this idea around since the start of the project, but there are a few issues. The stars could be cut up into sections and averaged by using an inverse tree. This is similar to what is done when rendering textures at further distances. This tends to create a flickering effect during the transition that I considered undesirable for the screensaver. It could be overcome completely by waiting until stars were less than an 8th of a pixel apart to use their average. This did not seem necessary for the screensaver as it is now, but this mehthod would be critical for a larger-scale application using millions of stars and a larger range of distances.
- Shane Reilly
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Shane Reilly
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Message 41330 - Posted: 8 Aug 2010, 19:19:40 UTC - in response to Message 41328.  
Last modified: 8 Aug 2010, 19:23:28 UTC

"Maybe it would help to look at the "abstraction" problem from the astrophysics point of view? You could merge stars based on their distance and mass/brightness once, and then use this abstracted dataset for the screensaver. If you are already looking at N-Body simulations, you could possibly re-use a spatial tree representation (like a barnes-hutt octtree); the end nodes of such a tree could be candidates for merging. Would it be possible to allow the user to control the amount of abstraction?"

-Frank

That is an interesting idea, and a commonly used one for physics approximations. Some physics team members of the MilkyWay@Home team suggested as you did to merge stars, while the computer science members tended to suggested skipping stars (I had the same idea). I tried skipping stars, however it became impossible to see the density distributions without increasing the size of the blurs. Losing the over-densities is undesirable since the point of the separation research is to match them to the stream. Increasing the size of the blurs creates similar overhead and makes things look "fuzzy" as one user pointed out which many people have indicated is also undesirable.

User control is simple to implement for any features you would like to recommend, either through an 'ini' file or through the use of function keys.
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Message 41334 - Posted: 9 Aug 2010, 0:46:14 UTC

An other vote for color.

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    Message 41338 - Posted: 9 Aug 2010, 9:13:04 UTC - in response to Message 41304.  


    I think that card [ATI 5850] should support doubles. Nearly all of the 5xxx series do, except randomly a couple don't.
    -- Matt


    I just looked up the specs on the ATI website. It seems that most of the newer cards support doubles, except for the Mobility cards.
    In a knowledge base article (http://developer.amd.com/support/KnowledgeBase/Lists/KnowledgeBase/DispForm.aspx?ID=88) they state that only the Mobility Radeon HD 4800 Series supports doubles.

    Mobility Radeon HD 5850:
    # TDP: 30-39 Watts (GDDR5) or 31 Watts (GDDR3/DDR3)
    # Engine clock speed: 500-625 MHz
    # Memory bandwidth: 64 GB/sec (GDDR5) or 28.8 GB/sec (GDDR3/DDR3)
    # Polygon throughput: 500-625M polygons/sec
    # Processing power (single precision): 0.8-1.0 TeraFLOPS
    (and no double precision...)

    Radeon HD 5850:
    # Maximum board power: 151 Watts; Idle board power: 27 Watts
    # Engine clock speed: 725 MHz
    # Memory bandwidth: 128 GB/sec
    # Polygon throughput: 725M polygons/sec
    # Processing power (single precision): 2.09 TeraFLOPS
    # Processing power (double precision): 418 GigaFLOPS

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    Message 41411 - Posted: 12 Aug 2010, 9:55:57 UTC - in response to Message 41338.  

    ...they state that only the Mobility Radeon HD 4800 Series supports doubles.
    Yet they claim 128-bit precision on all operations on, say, the 530V line. Why bother?
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    Message 41425 - Posted: 13 Aug 2010, 15:02:34 UTC
    Last modified: 13 Aug 2010, 15:25:12 UTC

    First on topic another vote for color

    now offtopic: ofcourse not many mobility videocards support double precision..
    the whole purpose of these cards is trying to give a good output with minimal heat and power draw ...
    lol what you think double precision do ;), mw is a super way to heat up your videocard and if its a laptop get it to shutdown because gets overheated xD
    All normal HD 5850 support double precision only the lower models seem to lack this but its sometimes hard to find if they support it or not
    I think the rule in this case is when they not mention it on the specs it probably is not implemented
    Its new, its relative fast... my new bicycle
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    Message 42154 - Posted: 15 Sep 2010, 3:52:00 UTC

    I see its been 32 days since last reply..any updates on the screensaver release?
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    Message 42351 - Posted: 24 Sep 2010, 19:02:13 UTC - in response to Message 42154.  
    Last modified: 24 Sep 2010, 20:04:21 UTC

    I am back on the project after being unexpectedly pulled away on personal business for some time. Demos will be released in the next few weeks. Testing is needed for all platforms before the first release.

    If you would like to test a quick demo to see if the application will run on your machine, feel free to try this and post your results (and specs if applicable):

    http://www.rpi.edu/~reills2/mwdemo/ (Windows - all versions)

    Usage:

    < / > - Move in / out
    F1-F9 - Change speed
    Arrow - look around
    Ctrl-arrow - spin view
    Shift-arrow - rotate object
    Tab - Start over

    You should see a blue blinking cube for the test.
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    Message 42358 - Posted: 25 Sep 2010, 3:28:15 UTC - in response to Message 42351.  

    I see multiple blue dots in almost all views but none look like a cube.


    Intel q6600 quad, Asus p5k deluxe, 3 gig ddr ram, 4850 ATI video.
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    Message 42433 - Posted: 28 Sep 2010, 19:37:31 UTC
    Last modified: 28 Sep 2010, 19:38:28 UTC

    Indeed, lots of pretty blue bubbly things fading in and out. They sort of form a cube together, but not really. I also managed to break it at some point - pressed > and everything went black aside from the axes at the top.
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    Message 42438 - Posted: 29 Sep 2010, 0:00:14 UTC - in response to Message 42433.  
    Last modified: 2 Apr 2011, 5:53:41 UTC

    Thank you for the feedback. I would be especially interested in computers that do not show anything, but feel free to comment on working runs as well. You can press to get back to the start. If the speed is turned up too high (e.g. ) it will zoom out so fast that nothing will be visible in a single frame. I do not expect the application will crash although using axes still has a couple bugs as you zoom in very close. Whether or not keyboard inputs and screen updates work is the main focus. The object is not literally a cube of course. It is an arrangement of glowing blurry stars in a cube formation.

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    Message 42443 - Posted: 29 Sep 2010, 8:21:20 UTC
    Last modified: 2 Apr 2011, 5:54:46 UTC

    Here are two new versions of the test in a zip file. Just extract the file to your desktop (or anywhere else you prefer) and run the two application files. Both files are the same program, but one runs in full-screen mode. If "cube_test.exe" runs on your machine, try the full screen version. As a precaution, it may be wise to close other applications and save work before running the full-screen test.

    For those that are not running Windows XP or later, downloading an application such as 7-zip or WinZip will allow you to extract zip files.

    cube_test_win.zip

    Usage:

    < / > - Move in / out
    F1-F9 - Change speed
    Arrow - look around
    Ctrl-arrow - spin view
    Shift-arrow - rotate object
    Tab - Start over
    Backspace - focus on center of cube

    Edit: Space to stop motion

    Yous should see an arrangement of glowing blurry stars in a cube formation as you zoom out. Speed is recommended for this.

    Please post results of the test and specs if the applications did not run properly if you would like to contribute to the screensaver testing. Tests with the stand-galaxy simulation will also be available soon.
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    Message 42449 - Posted: 29 Sep 2010, 15:15:04 UTC - in response to Message 42443.  
    Last modified: 29 Sep 2010, 15:20:54 UTC

    Wow, it's so psychedelic. Took me a while to figure out how to get it to work. The F keys only take effect once you actually press > or <, and once they do you can't stop it, only go faster or slower and switch between zooming in and out. F5 is a bit too fast for me, I'd recommend F4 (is this dependent on the speed of your PC?). It sort of ends up like an angry white blob - is that intended? The blue edges seem to be divided into two bands instead of a smooth transition, but maybe that's just how it works.
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    Message 42458 - Posted: 30 Sep 2010, 5:17:41 UTC - in response to Message 42449.  

    I have added a note that the spacebar will stop the camera motion. Thank you for pointing that out.
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    Message 42475 - Posted: 30 Sep 2010, 18:39:37 UTC
    Last modified: 30 Sep 2010, 18:53:31 UTC

    Ok got to the cube but my in out controls are < (out) > (in)

    Out meaning the cube gets smaller or further away and in means the cube goes to individual dots.

    Also the arrows move the cube opposite the arrow,,,,,,






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    Message 42699 - Posted: 9 Oct 2010, 7:35:00 UTC

    Sorry, my in/out controls </> do not work. Maybe because of german keyboard layout?
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