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Thread: Possible solution to VSync causing mouse lag

  1. #1

    Possible solution to VSync causing mouse lag

    *Please note that if your mouse is lagging even with VSync turned off, then there is another issue going on and this doesn't really apply to you.*

    Does tearing ( infuriate you? Want to use VSync to stop it, but don't want to suffer the mouse lag it causes? I might have figured out the cure for this dilemma.

    I was in this boat for about a week after the demo came out. I was extremely unhappy to have a $1000+ PC specifically to play UT3 only to be forced to deal with horrendous tearing that made the game very unpleasant to watch. I was in a bind: play with tearing with no mouse lag or play without tearing and not be able to hit sh*t. Obviously I had to pick the latter if I wanted to be competitive, but I was determined to find a way to have my cake and eat it, too.

    First off, the full version of UT3 may have a "ReduceMouseLag" option which could make the solution that follows irrelevent. I could play with VSync ON in UT2004 with ReduceMouseLag=True, and I didn't notice any mouse lag. But, if not.....

    I spent probably a dozen hours dedicated to researching this problem and coming up with the solution. Nothing in my research fixed the problem by itself, but it does factor in the final solution.

    I have an nVidia GeForce 8800 GTS 640MB. I don't know if this will work for ATi folks or not.

    So now I will give you the final results of my hours of research/testing:

    1) Turn VSync ON.

    2) In UTEngine.ini, set "bMaxSmoothFramerate=True"

    3) Set the "MaxSmoothFramerate" to a value that is very close to, but not above, your monitor's refresh rate. My monitor is a 20" widescreen with a refresh of 60.1 Hz. So I set "MaxSmoothFramerate=59.90".

    4) Download Rivatuner and install it.

    5) Find the "Pre-Render frame limit" option in Rivatuner and set it to something lower than 3. Don't use 0 though.....doing that caused UT3 to crash my PC immediately. (I'm actually not sure this is completely necessary, but I had already done it before finding the complete solution, so I just left it as it was)

    6) Go to the "Tools" folder wherever you installed Rivatuner and open D3DOverriider.exe. Add UT3Demo.exe to the list and make sure all the checkboxes to force Triple Buffering are checked.

    7) Now load up the UT3 demo and see how it goes.

    For me, it eliminated the tearing and diminished mouse lag to the point that I can't notice it. I can't say I'm 100% sure that there is absolutely zero mouse lag, but it certainly is not noticable by me.

    There were suggestions in my research about turning off Mouse Smoothing, but this didn't work for me. If VSync was enabled, the mouse lagged whether I had mouse smoothing on or not. You can try turning off mouse smoothing in addition to these other measures if you still notice lag, and see if it helps.

    The triple buffering helps the situations in which your fps drops below the refresh rate. Normally, when VSync is enabled, your framerate will try to drop more dramatically because of the "double buffering" phenomenon. Assuming a refresh rate of 60Hz, triple buffering would make it so that your framerate doesn't drop to 30 fps just because your system can't quite render 60 fps. Without triple buffering, it wouldn't be possible to get a framerate of 50 fps for example. More info here:

    You could leave VSync off and just use the MaxSmoothFramerate option to cap the framerate to your refresh, but this will not eliminate tearing. Tearing will be reduced (it won't be as bad as if you're getting 100 fps with a refresh of 60 fps), but not eliminated.

    I can't explain why the mouse lags when you just enable VSync without capping off the framerate in the .ini file. I guess it is something to do with the combination of VSync converting the framerate down to the refresh rate. When the system isn't even trying to render more than the refresh rate, it doesn't have to do this. Maybe that's the reason.....I just know it worked.

    Anyway, I hope this helps you like it helped me. It makes for a much more fluid gaming experience. If you try it, then make sure to post here and let us know if it worked for you.

  2. #2
    what happens if you turn off V-Sync and mouse smoothing?

  3. #3
    Quote Originally Posted by Uchiha_Itachi View Post
    what happens if you turn off V-Sync and mouse smoothing?
    Then you still get the tearing effect. VSync is the only way to stop tearing.

    Mouse Smoothing doesn't cause lag for fact, it feels more precise with it on. YMMV.

  4. #4
    hrmm interesting, I'll have to try it. Although I still get horrendous mouse lag with Vsync off, because I could care less about 'tearing'. Doesn't seem to jive with your theory if vsync off fixes the mouse lag anyhow.

  5. #5
    This is for fixing mouse lag problems caused by VSync. If your mouse lags even when VSync is off, then there is some other issue and none of this is likely to fix your problem.

  6. #6
    First off, nice to see that kind of intensity around vsync study...I did something similar a couple of years back. Lag CAN BE a very personal, perceptive-sensitive thing however...for example, I absolutely WILL NOT use an LCD to game - I find the lag to be far too excessive for me to bear (and I am talking 2ms response times - if anyone is offended by this, then GOOD - you should be )...I expect higher standards from this community! ...LCDs definately have some of their own advantages so don't get me wrong (intensity, etc.)...but if you are dead serious about PERFERT SMOOTHNESS, then you should consider a high-end CRT for gaming purposes only if you have the space (21" Sony F520, G520 or 24" FW900 for example...$1,700-$2700 MSRP when hit the market, but dirt cheap on ebay now.)

    Though I understand the theory of what you are saying, I am always interested in trying things out (even though I know T-Buff traditionally causes some lag as well as vsync...and reducemouse lag definately helps, but at an enormous FPS cost (and even then all the lag isn't gone))...if you tell me you're on a CRT, I will definately mess around with this summore (even though I've exhausted it...and I would definately want no less than 90fps so would have to up the caps). If however you are on an LCD, I've got to be honest in saying that I won't actually take this post seriously as I am extremely lag-sensitive and if LCD lag isn't bothering you, then neither would traditional T-Buff/Vync lag even with reducemouselag on most likely. Tearing is EXTREMELY annoying though and another alternative I found was just simply using higher-end hardware and keeping my FPS above 100 in the most intense rendering is not possible at the moment in UT3 due to hardware limitations - it is now 9 years later and I am FINALLY completely satisfied with UT99s performance...but I run the game at 2048x1280 8xAA 16xAF, 48KHz audio, MAX quality on everything + a lot more. With the accelerated hardware advances today, hopefully UT3 will be where I need it in 2 years lol. Also, despite what others have said (people that I consider "insensitive")...1000Hz mouse polling is a MUST - that means NOT 500Hz, NOT 250Hz, and definately NOT the default of 125Hz...if you don't already have this enabled you can check my other thread on this out here: ...good luck, and good work!

  7. #7
    I don't know if anyone has said this or not...

    1. Turn on VSync.
    2. Turn off triple buffering.

  8. #8
    Quote Originally Posted by 3NVY View Post
    If however you are on an LCD, I've got to be honest in saying that I won't actually take this post seriously as I am extremely lag-sensitive and if LCD lag isn't bothering you, then neither would traditional T-Buff/Vync lag even with reducemouselag on most likely.
    Yes, I use an LCD.

    I find your post a bit insulting, since you're basically telling me that I was simply imagining the lag I was getting before......just because I'm using an LCD. Yes, I spent a dozen hours fixing an imaginary problem. Whatever.

    In my case, this solution HELPED my game performance. It's smooth (to my standards, which I thought were pretty high until you revealed yours) and I don't have any noticable lag. I did not claim this would magically work for everyone as well as it has worked for ME. I am simply sharing it with others in the event that it could help THEM also.

    I don't even think you read the link I posted that explains triple buffering. Forcing triple buffering does not cause lag on any graphics card that's less than like 3 years old.

    I'm not going to go get a hundred pound monitor that takes up 5 times more space just so I can get a 100% perfectly smooth gaming experience. Yes, I also notice some visual blurring of colors when moving very fast on an LCD, but it's really quite minimal and I do not feel it is enough to affect my skills nor the enjoyment of the game. It certainly isn't bad enough for me to ditch it and get a gigantic CRT. I also like widescreen, and widescreen CRT's are rare.

    Anyway, VSync was the cause of my mouse lag.....not the monitor. I was smart enough to try out a CRT from where I work to make sure my LCD wasn't the culprit. I didn't mention this because I felt the post was too long already. And guess what......same lag. It was some CyberVision 19" piece of crap CRT that actually died after several hours, but that doesn't really matter. The lag happened exactly the same way in precisely the same situation. VSync, in general, causes mouse lag. Google it.

  9. #9
    Quote Originally Posted by LagMasterSam View Post
    I don't know if anyone has said this or not...

    1. Turn on VSync.
    2. Turn off triple buffering.
    Please read the thread before posting. It's not like it's 10 pages or something....

  10. #10
    ...well, that's what I said - VSync will cause lag...T-Buff will lag you too especially during DIPS (complex rendering moments where framerate drops)...I actually own a 20" widescreen LG 5ms monitor (and have tested many 2ms units as well to satisfy my curiousity)...I am untra-senstive yes (be warned) and to me the ghosting/lag is absolutely horrific and unacceptable...this will MAGNIFY the mouse lag in a perseptive way (not physically)...but the mouse lag will seem worse than it even is. Nothing personal...I have been on this rampage since 8ms lcd monitors when people were declaring 'it's all ok now'.

    Watch a car go by (close up) on the street while turning your head fast (yes you will look like an idiot) - THAT'S how a perfectly setup system should look like (just for reference)... :/

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