Wednesday, August 31, 2011

Mouse DPI & FPS Gaming

 A lot of "pros" will tell you that a high resolution (DPI) mouse setting won't improve your game. I believe this statement is true, but not in the way you may think. Browsing forums and product reviews, I've found there to be much confusion about the matter.

  The mentality of the "Gaming Mouse" market today is generally that the higher the DPI the better. A statement from SteelSeries suggests it's not as important as everyone thinks. However, they offer mice at 11,400 CPI (DPI). I suspect this is simple market competition. The option is important however, as I'll explain later.

  DPI setting is preferential. It isn't necessary to have a 5,700 DPI resolution if you can place your crosshair over any pixel on your screen at 400 DPI. The problem comes when you're uncomfortable with moving your hand large distances quickly, or simply don't have the space on your mouse surface to react quickly and precisely to targets. Basically, if you don't want to fling your hand across your desk to move your crosshair across the screen, you need higher DPI.

  But why not simply turn up the sensitivity in game you ask? Well, let's say that your sensitivity in game is set to 1 and for the purpose of simplicity we'll assume it's a 1:1 ratio. No matter what resolution your mouse sensor is, every time it reports a change in the image, your crosshair in game is going to move one pixel. You're going to have to move your mouse a ridiculous amount to turn 180 degrees, or use mouse acceleration to your advantage and really fling it pretty fast. Some people do this, and it works well for them. This is a matter of preference. However, if your preference is to do a 180 degree spin or more with a moderate speed wrist movement, you'll have to turn up your sensitivity. The problem with simply increasing the sensitivity using in-game software is, when you change your sensitivity from 1 to 2, you're essentially making it impossible to place your crosshair/reticle on half the pixels on your screen. This isn't a problem if your targets will never take up less than two pixels on your screen at a time. If your preference falls on an sensitivity high enough that your reticle is skipping over your target making it impossible to place a precision shot, a higher DPI setting is required. I've prepared a graphic example below.

  Basically you want just the right amount of DPI to maintain your sensitivity preference, yet still be able to place a precision shot anywhere on the screen.

  Choosing the right polling rate relative to your DPI is also important. With a DPI of 5,700 and a polling rate of 125Hz you'll notice that a disproportionate correlation between distance you move your mouse at different speeds and what happens on screen. Mouse input can be bottle-necked by insufficient polling rates. In other words, your computer can't tell how fast you're moving at such a high DPI. The disadvantage of using a high polling rate is CPU usage. It's not going to overload your CPU, but when your CPU is under load it may cause inconsistencies in sensitivity. I've also heard of certain games being particular about it. I haven't really experienced this personally.

  Sometimes certain games may have wonky mouse settings, and may require strange DPI/Polling rate settings. Console ports particularly suffer from this problem. Battlefield: Bad Company 2 is a perfect example. When I first got the game, I was trying to set it up for my mouse at 1600 DPI @ 125Hz. The problem was, no matter what settings I tried, it still skipped pixels. I modified the config files and it got a little better, but I was still skipping over people at long distances and found my self tapping my strafe key to put my reticle on them. To solve this problem, I set my mouse to it's highest settings (5700 DPI @ 1000Hz) and it was as smooth as butter. I believe this is due to overly complicated joystick emulating mouse input code.

I'm no expert but:

     if( joystickpresent ){ joystick code }else{ mouse code }

  Then we have games like ArmA 2, where there's a cap on how fast you can move your mouse. This has nothing to do with joystick emulation, but realism. I could argue how to better emulate realism rather than capping the mouse input but that's a rant for another time.

  In summary, keep your in-game sensitivity low enough to place your reticle anywhere on the screen, and adjust your DPI to a sensitivity you prefer. If a game has weird mouse settings, just tweak it until it feels good to you.


  1. Great post. My friend recently got a RAT7 mouse and that suddenly made him better at BF3 so I was very curious and looked up on mouse settings and DPI and all the stuff I've never thought of before when using a mouse but your post made a whole lot of sense. Thank you!

  2. Very helpful description of this gaming mouse as I am looking to buy a gaming mouse.. It helps me a lot to enhance my knowledge, I really like the way the writer presented the content.