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Framerates Matter
An anonymous reader writes "As more and more games move away from 60fps, the myth of the human eye only being able to detect 30fps keeps popping up. What's more, most people don't seem to realize the numerous advantages of a high framerate, and there's plenty of those."
Not sure how much it matters to sales, though.
Looks like it's Slashdotted already. Here's the cached page: http://74.125.47.132/search?hl=en&q=cache%3Awww.significant-bits.com%2Fframerates-do-matter&aq=f&oq=&aqi=
Your eyes introduce blur due to the reaction time of the light-sensitive cells in the retina. Fortunately, the image processing area in your brain treats blur introduced by the eyes and blur built into the frame more or less the same, so you can use blur to give the impression of smooth motion with a lower frame rate than would otherwise be necessary. This is used to good effect in cinema, where the camera's exposure time naturally introduces blur that is quite similar to the one introduced by your eye.
In the case of video games, however, it is not so clear that rendering effctive artificial motion blur saves much processing time compared to simply rendering more frames. Then again, there is a limit to how fast your monitor can update its image, so rendering more frames is no longer an option past that point.
But, if you follow the hand with your eyes, your hand will appear sharp. You'll be supprised how quickly and stable eyes can track moving objects.
The BBC has been experimenting with fast frame rate TV, running at 300 frames-per-second. Moving objects will appear much sharper with such a broadcast compared to the standard 50 frames-per-second (not fields). They showed a side by side example, both were 1080 progressive scan. Great for sports broadcasting.
Also Silicon Graphics (when they were called that) have done test with fighter pilots when designing flight simulators. Motion sickness is a problem with those flight simulators, compared to an actual jet plane. When they got a constant frame rate above 80 frames (160 frames per second when doing stereo imaging) per second the motion sickness was greatly reduced. They solved the processing power problem by being able to reduce the rendering resolution on each frame.
I am a visual neuroscientist (IAAVNS). The standard idea of refresh rate comes from CRT based monitors where the image is drawn by a scanning electron beam. If you use an instrument to measure the instantaneous brightness at a given point on the screen it will rapidly peak as the beam swings by, and then decay as the phosphor continues to release absorbed energy in the form of photons. Different monitors have different decay rates, and, typically, CRTs that were designed for television use have pretty slow decay rates. CRTs that were designed for computer monitors typically have faster decay rates. If the decay rate were very very fast, then the hypothetical point on the screen would be dark most of the time and only occasionally very bright as the beam sweeps by on each frame.
As you can imagine this highly impulsive temporal profile is hard to smooth out into something closer to the constant brightness of the world around us. The human retina has an inherent dynamic response rate to it, but it's actually quite fast, and there have been studies showing clear responses in higher order visual areas of the brain up to 135 Hz. But standard phosphors used in CRTs have a little smoother response, and so at more-or-less 80 Hz, the brain stops seeing the flicker (at 60 Hz most people see flicker on a computer monitor). The exact refresh rate where perceptual blurring happens (so the flickering goes away) varies widely between individual, and with the exact details of the environment and what is being shown on the screen. More-or-less at 100 Hz refresh, no one sees the flicker anymore (although the brain can be shown to be still responding).
Contemporary screens, however, are LCD based (I'm going to ignore plasma screens since the field is still working out how they interact with the visual system). Making the same experiment as above, the temporal profile of brightness at a given spot on the screen will look more like a staircase, holding a value until the next frame gets drawn. This is a far, far smoother stimulus for the visual system, so a 60 Hz frame rate produces a perceptually far more flicker-free experience. That's why most CRTs at 60 Hz make your eyes bleed, while LCDs at 60 Hz are just fine.
Except that newer LCDs have LED backlighting which is no longer constant, but flashed (WHY? WHY? WHY? Just to save some power? Please, computer manufacturers, let *me* make that decision!), so the experience is somewhat more like a CRT.
So that's one part of the equation: flicker.
The other part of the equation is update rate, which still applies even there might be no flicker at all. Here, we have the evidence that the brain is responding at up to 135 Hz. In measurements made in my lab, I've found some responses up to 160 Hz. But the brain is super good at interpolating static images and deducing the motion. This is called "apparent motion" and is why strings of lights illuminated in sequence seem to move around a theater marquis. The brain is really good at that. Which is why even a 24 Hz movie (with 48 Hz frame doubling) in a movie theater is perceptually acceptable, but a 200 Hz movie would look much more like a window into reality. On TV you can see the difference between shows that have been shot on film (at 24 Hz) versus on video (at 30 or 60 Hz). Video seems clearer, less movie like.
For games, 60 Hz means 16 ms between frame updates -- and that can be a significant delay for twitch response. Further, modern LCD monitors have an inherent two or three frame processing delay, adding to the latency. As we know, long latency leads to poor gameplay. Faster updates means, potentially shorter latency, since it is a frame-by-frame issue.
So, just as with audio equipment where inexpensive low-fidelity equipment can produce an acceptable experience, while a more expensive setup can create the illusion of being at a concert, so too inexpensive video equipment (from camera to video board to monitor) can produce an acceptable experience, while a more expensive setup can create the illusion of visual reality.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
more accurately - most film cameras don't have a notion of a shutter 'speed'.
The film roll still goes by at 24fps, but the actual shutter is a wheel. That wheel can have various sizes of gaps (to increase/decrease exposure *time*) and sizes (to produce specific motion blur effects; e.g. an object leading its own motion blur path requires a small shutter opening at first, ending in a large shutter opening). You use fairly sensitive film and a small shutter gap, and you'll get nearly motion blur-less shots like that of Saving Private Ryan (watch explosions in that film and every speck of dirt that gets thrown about appears almost razor-sharp; some find this objectionable). Heck, you can even expose twice per frame if you want to get all experimental and stuff.
That said.. you can't - short of electronic shutters - expose for -more- than the film's fps, though. A bit under 1/24th of a second is the most you'll get (that 'bit' being required to transport the film to the next frame).
Anyway.. wiki: http://en.wikipedia.org/wiki/Rotary_disc_shutter
I'm a neuroscientist that covers sensation and perception and its bidirectional interaction with cognition, particularly attention. I've got comments and questions and very few answers after reading this. I'm seeing a lot of things stated as facts that I've never heard of before. Some of them make sense, and some don't. Some of them are correct, some not, and many more than the others combined I have no experience in and can't say. Those seem to be well supported, or at least well known, particularly among those who've obviously done their homework. I can find references to these among the publications (like ACM) that are most applicable to the field in question, but I can find precious little in my customary pubs and books. That's not to say the stuff in the technically oriented pubs is wrong, just that some may not be covered much (ie. 'not of interest') in my field. My field is very cautious about experimental evidence, but I suspect in gaming's perception area there are common knowledge kids of things that came from hear say (we have many of those in rocketry too). It might do well for both fields to compare works.
What catches my eye at first is this "myth". As stated it's overly simplistic. Which humans' eye? Some have different reaction times. Those who could probably detect 30 fps discontinuity are those who see the TV screen jiggle and waver when they chew something crunchy while watching (you know who you are, here's a place to own up to it). What part of the visual field, central or peripheral? They operate differently. Jittering or blurring of objects attended to or not? Betcha it happens more to those not attended to, but that's not noticed for the same reason (hypnosis can bring that out right nicely). And how is it frame rates matter when the visual system evolved as a constant flow analog system? If a phenomenon that shouldn't make a difference does, and that frame rate is strictly due to technical considerations, how do we know that a variable frame rate might not give even better results? Since the visual system does not have full-field frames that refresh, why should artificial presentations? Why not present faster moving objects at a high change rate, slower moving at a slower rate, more or less a timing equivalent to some video compression techniques? Some of this makes good sense from my perspective, some appears goofy but may not be, and some clearly is whack according to well supported experimental evidence from my side, not sure about yours.
Here's an interesting one, apparent motion from blurring, occurring at the retina, ostensibly due to 'reaction time' of light receptor cells (rods and cones). I can see how this might occur. But if it's a time lag that causes blurring, everything should be blurred, because the layers of cells of different types in the retina between the receptors and those firing down the optic nerve operate strictly by slow potentials -- there's not a 'firing' neuron among them. Or, if their processing, though slow, accounts for motion and compensates, preventing adding to the blurring, how can that be used to increase apparent motion?
A last point which I'm fairly certain isn't covered in gaming and graphics presentation because very few know much about it and we don't understand it well: 10% of the optic nerve is feed-forward, top down control or tuning of the retina and its processing. Motion perception can be primed, can suffer from habituation, and has variance in efficacy according to several factors. What cognitive factors have an influence on this, and how can that be used to improve motion perception and/or produce motion perception that's as adequate as what's being used now but requiring less external computational effort because internal computation is being stimulated.
It's probable that both fields have things of interest and use to the other, including things the other isn't aware of. I've said much the same following another article on a different subject. From this one I can see it's probable there's a few peoples' careers worth o
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
You didn't even read your own link. So for the benefit of people who may stumble upon your misinformed post let me say that the wagon wheel effect is visible with the naked eye under continuous illumination, which happens to be mentioned in your own link.
The question of whether a computer can think is no more interesting than the question of whether a submarine can swim.