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Vista GUI question
- Thread starter Brassbud
- Start date
MrChad
Lifer
AFAIK, vsync means that screen updates are limited to the refresh rate of the monitor / video driver. In other words, if you're running at 75 Hz and have vsync enabled, your frames-per-second will be limited to 75. You can disable vsync and get higher refresh rates, but you also get graphics tearing side effects.
http://www.d-silence.com/feature.php?id=255
It's only a 3D issue I believe, so I have no idea what the OP is talking about.
spyordie007
Diamond Member
Yeah I'm not sure either; I was under the impression that it's mostly dependant on your video card, its drivers and the display adaptor.
It sychronizes the frame output from the video card to the refresh rate of the monitor, essentially. With it off, you can observe something called "tearing" in which some contents of the screen which have not been refreshed yet are not aligned with the contents that have creating a visible horizontal seam on the screen.
Vsync prevents such tearing.
There is a nice description here.
spyordie007
Diamond Member
Right, but that doesnt clear up the question of what sync issue is the OP refering to.
SparkyJJO
Lifer
Ok that is what I've heard b4 - but I've never ever seen it (even with framerates well over 100 on some things). I was curious because I never heard of tearing in the XP GUI so I thought maybe I was mistaken. Apparently not, so how is there tearing in the XP GUI? Doesn't make sense
Its most noticeable on CRT because of how they draw images. The larger the change between frames, the larger the tear because the image being drawn on the top portion will be quite different from the previous image on the bottom (although my CRT appears to draw from the bottom. Because XP's GUI is 2D and runs increadibly fast, the tears are never that pronouced, but if you drag a window at the right speed given your refresh rate, you will get a nice stairstep effect (there is only one tear per refresh, but each refresh shows the tear in a slightly different place) Since Vista's GUI will use a more traditional DX9/10 renderer, and will run at lower frame rates than XP, in can and will need to use Vsync in order to avoid some ugly messes, so I hope it will have it, as well as AA/AF support as well.
The new Alt-tab feature will angled screens, AF will improve viusal quality of this and possibly other image reductions.
In regards to who whips their windows around all the time...I do, plus I have a picture of one of Jupiter's moons as my background, and so most of it is black...where as XP outlines things in a whitish grey, this is a large contrast and is therefore more distracting
In regards to who whips their windows around all the time...I do, plus I have a picture of one of Jupiter's moons as my background, and so most of it is black...where as XP outlines things in a whitish grey, this is a large contrast and is therefore more distracting
This doesn't sound like a 'vsync' issue.
The reason why Windows tear when you drag them around isn't because the drawing isn't in sync with your monitor it is because each frame the window has to be refreshed completely and your computer is not able to keep up with it. So some frames you see the window isn't drawn completely because it couldn't of finished it.
It's something that is normal with this sort of thing. In Linux it's a bigger issue, in OS X is has been solved for a long time.
Which is ironic because Linux draws the windows the fastest, Windows the next fastest, and OS X is the slowest. (if you ever using OS X on a not-so-fast machine you'll notice how the windows lag behind your mouse pointer if you drag them around quickly)
Vista will solve this with something called compositing. Linux already has had this feature for a while now, but it is usually disabled due to the lack of performance/compatability with it's 2-D drivers, future versions of Linux distros will have the option of IAGLX or XGL or releated items that use 3-D drivers to gain acceptable performance. OS X has always had this and at different times had different amounts of 2-D versus 3-D acceleration depending on the version of OS X your using.
What will happen is that your windows are drawn off-screen in a buffer. These buffers are used to generate textures that are then mapped, in 3-D accelerated systems, to 2-D rectangular primitives. Similar to a texture in a video game is mapped to a cube or a model.
Then the desktop is rendered as one big image using acceleration from your video card. (this also allows for speedy alpha transparencies and 3d manipulation, texture manipulations, and other special effects)
Thus windows won't be tearing anymore. They are a single big image and will only need to be re-drawn if you resize a window or interact with it.
This will reduce performance though.. for 3d items running in window mode (not fullscreen), especially. Since you have all that buffering going on. It will add some lag to your actions and window redraws, but it shouldn't be perceptable. However it will also reduce CPU load (if is done efficiently) since you will be utilizing your video card better and offloading some of the CPU load when it comes to drawing the windows and such.
Also in Vista you actually have disabled hardware acceleration using GDI when drawning windows in a off screen buffer. Compisition makes these things more difficult and is also probably causing the lack of compatability with OpenGL accelerated graphics in Aero mode.
The only odd thing about Vista is that with 3d effects on Linux all the demos and such are done on older machines.. We are talking about laptops using first and second generation ATI Radian cards. (like a ATI 7400 or 9000), the specs for Vista's Areo Glass calls for very modern cards and fast cpus, which is kinda odd. So obviously there is some more going on with Aero then what I am aware of. Most of what I know comes from Linux stuff.
But as far as the window tearing goes the compositing features of Aero for Vista should solve this if you have them enabled.
The reason why Windows tear when you drag them around isn't because the drawing isn't in sync with your monitor it is because each frame the window has to be refreshed completely and your computer is not able to keep up with it. So some frames you see the window isn't drawn completely because it couldn't of finished it.
It's something that is normal with this sort of thing. In Linux it's a bigger issue, in OS X is has been solved for a long time.
Which is ironic because Linux draws the windows the fastest, Windows the next fastest, and OS X is the slowest. (if you ever using OS X on a not-so-fast machine you'll notice how the windows lag behind your mouse pointer if you drag them around quickly)
Vista will solve this with something called compositing. Linux already has had this feature for a while now, but it is usually disabled due to the lack of performance/compatability with it's 2-D drivers, future versions of Linux distros will have the option of IAGLX or XGL or releated items that use 3-D drivers to gain acceptable performance. OS X has always had this and at different times had different amounts of 2-D versus 3-D acceleration depending on the version of OS X your using.
What will happen is that your windows are drawn off-screen in a buffer. These buffers are used to generate textures that are then mapped, in 3-D accelerated systems, to 2-D rectangular primitives. Similar to a texture in a video game is mapped to a cube or a model.
Then the desktop is rendered as one big image using acceleration from your video card. (this also allows for speedy alpha transparencies and 3d manipulation, texture manipulations, and other special effects)
Thus windows won't be tearing anymore. They are a single big image and will only need to be re-drawn if you resize a window or interact with it.
This will reduce performance though.. for 3d items running in window mode (not fullscreen), especially. Since you have all that buffering going on. It will add some lag to your actions and window redraws, but it shouldn't be perceptable. However it will also reduce CPU load (if is done efficiently) since you will be utilizing your video card better and offloading some of the CPU load when it comes to drawing the windows and such.
Also in Vista you actually have disabled hardware acceleration using GDI when drawning windows in a off screen buffer. Compisition makes these things more difficult and is also probably causing the lack of compatability with OpenGL accelerated graphics in Aero mode.
The only odd thing about Vista is that with 3d effects on Linux all the demos and such are done on older machines.. We are talking about laptops using first and second generation ATI Radian cards. (like a ATI 7400 or 9000), the specs for Vista's Areo Glass calls for very modern cards and fast cpus, which is kinda odd. So obviously there is some more going on with Aero then what I am aware of. Most of what I know comes from Linux stuff.
But as far as the window tearing goes the compositing features of Aero for Vista should solve this if you have them enabled.
smack Down
Diamond Member
I don't think that the effect has anything to do with Vsync. I think the effect has to do with double buffering.
spyordie007
Diamond Member
Thanks for the informative post Drag.
I don't exactly understand what you mean by this. I guess I was assuming this was a vsync problem because the exact same effect happens in other situations and is solved by vsync. Please explain not finishing drawing windows though, and the manner in which they are not completed, as I was under the impresson the windows were drawn many times faster than the fastest refresh rates (in the ~1500/s range). OS X has been render-to-texture since its implementation of OpenGL, which is also why its performance sucks.
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