Wrapping It Up
So there you have it. Triple buffering gives you all the benefits of double buffering with no vsync enabled in addition to all the benefits of enabling vsync. We get smooth full frames with no tearing. These frames are swapped to the front buffer only on refresh, but they have just as little input lag as double buffering with no vsync at the start of output to the monitor. Even though "performance" doesn't always get reported right with triple buffering, the graphics hardware is working just as hard as it does with double buffering and no vsync and the end user gets all the benefit with out the potential downside. Triple buffering does take up a handful of extra memory on the graphics hardware, but on modern hardware this is not a significant issue.
Just to recap, from our previous example, here are what the three frames we looked at rendering stack up side by side.
Triple Buffering
Double Buffering
Double Buffering with vsync
We've presented the qualitative argument and the quantitative argument in support of triple buffering. So, now the question is: does this data change things? Are people going to start looking for that triple buffering option more now than without this information? Let's find out.
{poll 135:300}
The major difference in the technique we've described here is the ability to drop frames when they are outdated. Render ahead forces older frames to be displayed. Queues can help smoothness and stuttering as a few really quick frames followed by a slow frame end up being evened out and spread over more frames. But the price you pay is in lag (the more frames in the queue, the longer it takes to empty the queue and the older the frames are that are displayed).
In order to maintain smoothness and reduce lag, it is possible to hold on to a limited number of frames in case they are needed but to drop them if they are not (if they get too old). This requires a little more intelligent management of already rendered frames and goes a bit beyond the scope of this article.
Some game developers implement a short render ahead queue and call it triple buffering (because it uses three total buffers). They certainly cannot be faulted for this, as there has been a lot of confusion on the subject and under certain circumstances this setup will perform the same as triple buffering as we have described it (but definitely not when framerate is higher than refresh rate).
Both techniques allow the graphics card to continue doing work while waiting for a vertical refresh when one frame is already completed. When using double buffering (and no render queue), while vertical sync is enabled, after one frame is completed nothing else can be rendered out which can cause stalling and degrade actual performance.
When vsync is not enabled, nothing more than double buffering is needed for performance, but a render queue can still be used to smooth framerate if it requires a few old frames to be kept around. This can keep instantaneous framerate from dipping in some cases, but will (even with double buffering and vsync disabled) add lag and input latency. Even without vsync, render ahead is required for multiGPU systems to work efficiently.
So, this article is as much for gamers as it is for developers. If you are implementing render ahead (aka a flip queue), please don't call it "triple buffering," as that should be reserved for the technique we've described here in order to cut down on the confusion. There are games out there that list triple buffering as an option when the technique used is actually a short render queue. We do realize that this can cause confusion, and we very much hope that this article and discussion help to alleviate this problem.
Facebook
Twitter
RSS
184 Comments
View All Comments
DerekWilson - Friday, June 26, 2009 - link
In game options for DX games are what we need to rely on right now, as there is no control panel option in a driver for this.It is possible to force triple buffering in some DX games through other means, but what is needed is game and driver developer pressure to get this feature into every game.
ukbrainstew - Sunday, June 28, 2009 - link
You'd be surprised the amount of games D3DOverrider works with, I find compatibility is easily over 90%.That developers don't include the option is really rather frustrating, though I just thank the PC community for coming up with a very good workaround as they invariably tend to do.
Another setting that I'd like to become standard is the ability to choose a framerate cap. Plenty of engines allow it (though its often locked away) and it can work wonders for increasing the smoothness and playability of games on older hardware.
Even sub $100 parts could maintain a damn near constant 30fps in most games at 720p resolution but they very well may struggle trying to hit 60fps often resulting in wild variances. Would it not be to the benefit of Nvidia and AMD's marketing if they could produce a driver level setting that caps games at half your refresh rate? A setting that would suddenly making their budget parts capable of maintaining a steady framerate in so many more games thus making them much more attractive products.
Anyway, thanks a lot for the article, triple buffering has been something of particular interest to me as I really can't bear a game with any appreciable amount of tearing and I'd really rather not suffer increased input lag and as much as a 50% reduction in my framerate when a simple setting can do away with it all in one fell swoop.
Could I suggest a mention of D3DOVerrider in the article? Surely giving readers advice on how to benefit from triple buffering in more games would be a worthy addition and something many may be craving now that they're armed with knowledge of its inherent benefits.
erple2 - Sunday, June 28, 2009 - link
I think the reduction in frame rate is to an even multiple of the maximum frame rate - You'll get 1 (refresh rate of monitor), 1/2, 1/3, 1/4, 1/5, 1/6 etc. and nothing in between with vsync on.I've noticed that in games that allow me to show the frame rate, I get exactly 60 FPS (I have an LCD monitor), 30 FPS, 20 FPS, 15 FPS, 12 FPS, or 10FPS (and so on) and nothing in between. But that's the way the vsync operates with double buffering.
With triple buffering, I can get more or less any FPS rate lower than 60.
fiveday - Friday, June 26, 2009 - link
Yes. D3DOverrider is a utility that (as the name implies) overrides certain D3D calls and forces a few of its own settings. Specifically, it can force Triple Buffering and VSync (on or off) in any Direct 3D application. It comes with RivaTuner, but is a seperate app - you won't find it in RT's settings, but in it's installed folder as a standalone program.So yeah - download the latest RivaTuner (which you don't even have to run, tho it's useful!) and use D3DOverrider to force triple buffering in Direct 3D.
This saved my experience with Dead Space... and I've been singing it's praises ever since.
toyota - Friday, June 26, 2009 - link
I have to go ahead and laugh at the people that turn triple buffering on from the standard control panel and claim they see a difference. that setting has NO effect on DX games and is for OpenGL only. of course you have to use a third party app like rivatuner nhancer to actually force triple buffering on. its nice that some games like L4D have it built right into the game options though so that it is very convenient to enable from within the game without any third party crap to fool with.leexgx - Saturday, June 27, 2009 - link
Why is there not an Pole option for triple buffer with Vsync on and off or is the pole option ment for Vsync on with triple if so its Not what most of us would of pickedi allways run the games if i can with triple but No Vsync as the lag is to much
Vsync on has always made input lag be it 3 buffers or 2
Hrel - Monday, June 29, 2009 - link
pole is supposed to be poll, the way you mean. Confusing the way it is.The0ne - Friday, June 26, 2009 - link
For now, I just check the games to make sure there's an option for it. If not then I don't bother trying to find a way around it. Derek has it right, developers has to see the benefits and implement it if video card mfger's or MS doesn't implement it.DerekWilson - Friday, June 26, 2009 - link
This is the reason the last line of our article is focused on the developers.They definitely, like Valve, need to start including triple buffering in in-game options.
And it would be nice if NVIDIA and AMD could build something into the driver to make it work for everything. They put a lot of time into making AA work in most games, why not do the same for triple buffering?
GourdFreeMan - Friday, June 26, 2009 - link
I was under the impression that if you set VSync to "Force On" and Tripple Buffering to "On" in the nVIDIA control panel under the "Global Settings" tab you effectively force triple buffering on for all aplications, except those specifically excluded by their individual profiles. Is this not the case? This option has been available for years... admittedly I have never attempted to capture frames to verify that triple buffering is actually occuring.I don't see why this shouldn't work universally for applications -- as far as the application knows the only thing that has changed is the size of the pool of available graphics memory.