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In some FPS games the players view will move slightly from side to side (or up and down) when walking or running. This is known as “camera shake” or “headbob”, a so-called “feature” that is supposed to add realism to the game. The most extreme example that I’ve seen is in S.T.A.L.K.E.R : Shadow of Chernobyl, where the default camera shake can make your eyes hurt after 15-30 minutes of gameplay. in fact, this camera behaviour is not realistic at all.

It is true that in the real world people don’t glide around smoothly like hovering robots. When you walk or run your motion is never perfectly fluid, and your head (and point of view) will shake and shift. However, you probably won’t notice that slight shaking – your brain automatically compensates for it. In fact, that’s only one of the many post-processing tasks the brain performs on the raw input coming in through the optic nerves, but that’s beside the point.

So why doesn’t that work in computer games? If we can compensate for slight shaking in the real life, why does camera shake in games cause dizzyness – can’t the brain compensate for that, too? Apparently not. I suspect the problem is the first person view that FPS games offer isn’t “first person” enough to allow these compensation mechanisms to work. First, the field of vision is relatively small – the display only takes up some 1/8 of your natural FoV and underutilizes peripheral vision (which is more sensitive to movement). Second, your actual sense of movement and balance – things governed by that inner ear stuff – doesn’t match what you see on the screen. In effect, the brain gets two incongruous sets of data – one from the game and another from the world around you. This confuses the brain component that’s supposed to compensate for shaking vision and makes you feel dizzy.

Then again, I am not a biology major, so don’t quote me on this.

The take-home bit is that constant headbob is a bad idea in FPS games. The normal movement should be smooth, as that’s how it looks in the real world. On the other hand, camera shake is a useful effect in special situations, like emphasizing large explosions, or when the player is trying to aim precisely with a sniper rifle.

As for S.T.A.L.K.E.R, I found a few hacks and got rid of the headbob. A pretty good game, too.