Actually the eye only notices 15 frames per second.
Record anything at 15 frames per second, and than watch your recording. Considering that recording went smooth (e.g. there was enough free RAM) you won't notice any difference between 15 fps and 20 fps or 30 fps or 60 fps.
This is very wrong.
15 FPS is the boundry of constant motion, anything below that appears to be a series of changing pictures and above is detected as something is in motion. Human eyes can resolve up to 200 FPS before mothion quality stops improving.
Yes you can play a game at 15 FPS, but you will definatly notice how much smoother the movement looks at 30 FPS compared to 15 FPS. Like wise, you will notice how much smoother something looks at 60 FPS compared to 30 FPS. You will also likly notice how much smoother something looks at 120 FPS compared to 60 FPS but by this time you need specialist hardware and the visual returns is minimal (starting to vurge on the undetectable).
The reason CRTs and such technology work is that our eyes work by change of light. Although we are capable of seeing the flicker very clearly on CRTs we can not resolve it because our eyes get saturated by the brightness of it refreshing the display so that even when it is dark we are still receiving the image from it. Simlar principles to ghosting your eyes get if you look at something bright. Our cones have a very slow response time.
On the other hand, our rods have a much higher response time, capable of resolving up to 200 changes a second it has been measured.
So why do movies look so smooth despite being at 25/30 FPS? The answer is they include montion blur on each individual frame which imitates the mothion blur your cones produce when something is in motion even though it is actually part of the movie. As we can not resolve details of objects in motion any quality gained from using less motion blur at higher frame rate (sharpness) is not percetable.
Games on the other hand have problems producing accurate motion blur. As such each image is sharp which means that sudden changes from fast motion become noticable to our eyes as it exhibits behaviour of something moving stupidly fast to our brain. In order to get around this on the 360 and PS3 where all graphic intensive games are at 30FPS they use motion blur techniques but these result in artifacts like sharp backgrounds around object edges.
Our eyes are likly analog. This means that in reality they produce a constant stream of images instead of individual frames. The reason we can not resolve changes that are very fast is due to a combination of factors.
1. The rate of change of output from the perceptors (resulting in output smoothing for change frequiencies above a certain quantity). Cones have a lower rate of change compared to rods meaning that preceptable quality will be lost when exceeding certain change frequiencies.
2. Brain being wired to not resolve high frequiencies. In nature nothing from this world produces a high rate of change of light intensity meaning that it is pointless to be wired to cope with such inputs. Much simpler for the brain to just ignore such inputs or produce strange results (eg, why eplepsi might occur).
3. Interpreting data is intensive. The brain gets wired only to interpret things that mater. We can detect stuff like attacking animas at 1/200th of a second but trying to resolve a large page full of text even in 10 second is far beyond us.
A simple experiment to prove some of what I said that we can all do at home.
1. Make a new WC3 map.
2. Make 3 units in a line next to each other via script.
3. Use a timer controled system to move these units in a sin wave like motion with an offset for each one so they form rows.
4. Unit 1 gets updated every timer period, 2 gets updated every 2 timer periods and 3 gets updated every 4 timer periods with the position in the sin wave each unit assumes being universal at every timer peroid.
5. Set the timer to run at slightly over 60 FPS (0.0166 or 60.24 FPS).
6. Test the map. The multiplyer of the sin wave may need adjusting to produce a visable change.
You will notice the 15 FPS unit is appearling to teleport between points. The 30 FPS unit will appear smooth most of the time but at high rates of change it still appears to teleport. The 60 FPS unit will appear smooth all the time comparitvly.
