We often neglect to get too involved in the discussion of what options people should always enable when they play games. Rather, we tend to focus on what we test with. Honestly, our recommended settings for playing the games we test would be very similar to the settings we use to benchmark with one very important exception: we would enable triple buffering (which implies vsync) whenever possible. While it's not an available option in all games, it really needs to be, and we are here to make the case for why gamers should use triple buffering and why developers need to support it.
Most often gamers, when it comes to anything regarding vsync, swear by forcing vsync off in the driver or disabling it in the game. In fact, this is what we do when benchmarking because it allows us to see more clearly what is going on under the hood. Those who do enable vsync typically do so to avoid the visual "tearing" that can occur in some cases despite the negative side effects.
We would like to try something a little different with this article. We'll include two polls, one here and one at the end of the article. This first poll is designed to report what our readers already do with respect to vsync and double versus triple buffering.
{poll 134:300}
After reading the rest of this article, our readers are invited to answer a related poll which is designed to determine if arming gamers with the information this article provides will have any impact on what settings are used from here on out.
First up will be a conceptual review of what double buffering and vsync are, then we'll talk about what triple buffering brings to the table. For those who really want the nitty gritty (or who need more convincing) we will provide follow that up with a deeper dive into each approach complete with some nifty diagrams.
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SirLamer - Friday, June 26, 2009 - link
It's just because nVidia hasn't designed their control panel to be super invasive. The only way to make it work is to have a program sitting there that intercepts calls from DirectX and changes them.Rather than blaming AMD and nVidia, it's probably better to ask why DirectX doesn't include a mechanism to control this performance parameter like it does for most other driver-configurable settings.
Download Riva Tuner, and from the zip file install D3D Overider. It will sit on your taskbar and do the job. I have used this program in the past, but I forgot to put it back since my last reformat and will now do it tonight. Thanks for the reminder article!
GourdFreeMan - Friday, June 26, 2009 - link
Hmm... it seems you are correct.How bizarre! I can understand the usefulness in keeping previous frames for post-processing effects, but you would only be reading from the frames and writing to the new frame, never writing to old ones. Why doesn't this "just work" under the control panel for DirectX like it does for OpenGL?
smn198 - Saturday, June 27, 2009 - link
I suppose we have monitor refresh rates as a legacy from CRT technology. Is there any reason (other than comparability) why we can't have a LCD that refreshes ad-hoc, when both it and the next frame are ready? No more just missing a refresh.Alternatively could LCD lie about its refresh rate and have some sort of buffer internally to achieve the same thing - reducing lag?
GourdFreeMan - Sunday, June 28, 2009 - link
All LCDs (both passive and active matrix) still refresh the screen periodically to prevent individual pixel elements from fading, so there is still a notion of refresh rate for LCDs. You do raise a good question of whether it would be possible to refresh the screen whenever frames are completed (which would have to be in addition to this base refresh rate, or you would get a flickering in brightness).Having an input buffer to reduce perceived display lag would result in torn frames if you tried to swap in the new frame mid-refresh. You still have to wait until the refresh is completed.
erple2 - Tuesday, June 30, 2009 - link
That doesn't make sense from the perspective of how an LCD works. The charge that twists the polarizing LCD element doesn't fade over time (well, not over the few milliseconds between updates - though the charge probably fades over the years as they wear out).The pixel elements don't generate any light themselves. How do they fade then?
I think that you're confusing 2 things here. The refresh rate of the LCD is tied to the output signal - they're both set to run at 60 Hz, so the video card outputs a "new frame" (even if the frame hasn't changed, it's a new frame) ever 1/60th of a second. The LCD then reads that signal every 1/60th of a second and displays it. Part of the reason they chose 60 Hz is due to the bandwidth limitation of the set standard. To update more frequently than that, you'll clearly need the capability of transmitting more data down the interface. Right now, the DVI interface can transmit up to 3.96 Gigabits of info per second. at 24 bits per pixel, and a 1920x1200 resolution, that's 55,296,000 bits per image. Given the hard cap of 3.96 Gbps, that's 3.96/55296000 * 1billion which is about 71 Hz. That's the fastest a single link DVI interface can refresh at that resolution. I believe it was therefore decided to cap the refresh rate at 60 Hz for any WUXGA resolutions. But, that's out of convenience, not for any reason related to fading pixels (unlike a CRT).
LCD's don't flicker per se, as there's no light that's turning on and off. The backlight is more or less constantly on.
overzealot - Wednesday, July 1, 2009 - link
As the pixels untwist (no power applied, or power applied in reverse) they transition back to blocking light. You could, theoretically, call the process fading, as that's what it would appear to do.The backlights in most LCD's run off AC, you can't say they're always on. Best you can say is that because the frequency is much higher than 50/60hz you can't see the flickering. It's still there.
There are faster than 60hz panels, it's just that the electronics are more costly - and the majority of people don't care.
I do care, but not enough to pay the extra cost of a 120hz panel.
I'd rather have a larger panel.
DerekWilson - Wednesday, July 1, 2009 - link
it is my understanding that pixel state on an LCD panel is driven by a steady voltage applied across the liquid crystal cell (aside from possible overdrive on the upswing to increase transition time). because they are digital, until the controller changes the state of that pixel, it can remain at a constant percentage of twist because there is a constant voltage applied. no refresh is "required" and the bandwidth issue is what drives "refresh rate" on LCD panels.many LCDs do use CCFL for backlight which can have a slight flicker for a very very short time period every time current alternates polarity, but it isn't really ever "off" as they are driven both ways (there are no dedicated anodes and cathodes - they switch with current).
But as we move toward LED backlighting (or away from CCFL and toward other technologies which are DC) then we won't have any flicker at all there either.
GourdFreeMan - Monday, August 31, 2009 - link
This "steady" voltage (only true of active-matrix LCDs) isn't maintained directly by the LCD's power supply. For TFTs there are one or more capacitors gated by a transistor for controlling their voltage per pixel element (R,G,B) that maintains the state. These capacitors slowly discharge and must be refreshed periodically. In this sense all LCDs have a "base refresh rate".If you do a Google search for LCD controllers integrated into consumer products you will find there is an issue with perceived flickering in brightness as the pixel elements fade if you do not refresh them often enough.
I was asked if it was possible to refresh the screen only when frames are completed, and this was the first issue I discovered when researching the question. Other than increased power usage and added controller complexity I do not know if there would be other issues if you tried to do a second "just in time" refresh and left my reply to the original question at that.
RSmith - Thursday, April 8, 2010 - link
Hey GourdFree Man,I got here thinking exactly the same thing as you: why do we need a fixed refresh rate on LCD's?
Did you get any answers to that?
I hope that future display technologies will allow this to happen, it would certainly be of huge benefit to gaming if frames were drawn as they were rendered.
homerdog - Sunday, June 28, 2009 - link
I can set my LCD to 75Hz, which AFAIK is a lie.