First of all, I don't perveice Movies in a Cinema as "fluid" (I can see the tricks they use to try to fool the human eye, it's especially visible with rapid camera motion - the Motion Compensation hits its limitations)
Now, for a slow Strategy Game, I can easily accept 30-40 fps (but not for controls, for example... nothing bugs me more than a mousepointer stuttering around at that low rate)
From personal experience :
From 3D shooters in a competitive play (Internet), I demand around 60fps minimum, it starts bugging me big time if it's below that.
In close-quarter "death around every corner" type Games, I'd rather have 100-120fps to reach fully intuitive interaction and control.
Playing that with 40fps instead would mean frequent death and a good deal of frustration.
(I know Quake 3 Arena international tournament cracks have their systems setup to
never drop below 150-200fps, because that's what their lightning fast reactions are tuned to after years of training)
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AFAIK, it's not the human eye that is limiting anything, it's the human brain which primary job is to filter unneeded information out of the massive Video Stream and concentrate/repackage/give sense to the Details of Interest.
In fact, the human brain can (given some time) completely modify the Image the eyes are delivering.
There were numerous experiments, one of the more remarkable involved volunteers carrying Glasses that would flip their entire field of view upside down.
After an average of 2 weeks (and a hell lot of sickness / turned stomaches later), all volunteers had gained the ability to see "normal" again.
Their Brain had adapted to the new situation and flipped the Images again.
(naturally, after the exeriment was ceased and glasses taken off, the ordeal repeated - as the volunteers were seeing everything upside down again, just this time without glasses
)
Basically, with sufficient training the fps the
brain can detect and work with can increase tremendously.
The TV and Movie examples (25-30fps) are possible only with Motion Compensation that blurs it enough so the human brain is able to complete the stuttering animation on its own - that's one of the brain's most powerful functions, testable for everyone on a wide series of Visual Experiments that demonstrate the brains abilities and shortcomings - some of which are quite funny.