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Brain Trickery?

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I know that for most purposes it's desirable to have at least 30 FPS for a scene to be smooth. With all of the talk in the forum about photon tracing, I followed a link to OpenRT, which I found pretty interesting, but they said that the most they're able to get out of a scene using OpenRT is around 22 FPS. This is pretty good, but you'd probably notice some points that aren't smooth. I'm not sure what really sets the refresh rate for our eyes, whether if it's a physical limitation with the eye itself, or if it's a timing sort of thing in the brain, but if it's the latter, has their been any experimentation into resetting this refresh rate? I've had some experience with something called binaural beating, which is where one frequency is played in one ear and another, slightly different, frequency is played in your other ear. The brain combines these different frequencies and you start to get synched up with this frequency difference resulting in some interesting sensations and experiences [grin]. Could something like this work in graphics? Fooling the brain into thinking the image it's seeing is refreshing itself faster or that it's smoother? I really have no idea about this, but I was just thinking that if something like this were possible, performance issues could become less of a worry. Any thoughts?

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I took a course on human vision. The eyes are limited by how fast your cones can "refresh" themselves. That is, there is a degree of persistance, when you see a light stimuli. It doesn't instantly go away. There is also the fact that motion detectors in your brain are tuned to detect motion up to a certain speed limit. Finally, neurons aren't extremely fast either, so they can't get information at infinite speed.

I can tell you one thing, however. 30 FPS is not enough, at least not what a videocard generates. Why? Because these frames produce aliasing in time. When you watch a movie at 30 FPS, the images have blur, which is sort of timewise antialiasing. When you look at a videogame, the positions instantly change from one frame to the other, which produces a jump like effect. Human eyes can detect flickering at up to 60 FPS, on average (higher for some individuals). So 30 FPS might look smooth in a movie, but in a video game, you need something in the order of 60+ FPS for it to truely look smooth.

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Set your monitor to 60hz and look past it. You will likely find you can see the flicker out of the corner of your eye (peripheral vision is very good at sensing movement). Set it to 70hz and it will go away, even looking directly at it will feel nicer. Doesn't sem to work with lcd's though, they blur. I'm not sure what the 'refresh rate' of your eye is, but it's pretty high.

The only thing I can think of to trick the eye is update the screen in patterns, like you do every second pixel in a checker pattern. And that would look terrible if the rate was low enough that you could see what it was doing.

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Original post by RAZORUNREAL
Set your monitor to 60hz and look past it. You will likely find you can see the flicker out of the corner of your eye (peripheral vision is very good at sensing movement). Set it to 70hz and it will go away, even looking directly at it will feel nicer. Doesn't sem to work with lcd's though, they blur. I'm not sure what the 'refresh rate' of your eye is, but it's pretty high.

The only thing I can think of to trick the eye is update the screen in patterns, like you do every second pixel in a checker pattern. And that would look terrible if the rate was low enough that you could see what it was doing.


The reason is that peripheral reason is not0 based on cones (they are onlyu present in low density in peripheral areas), but almost entirely on rods. Rods are very fast to adapt to light intensity changes. They are in low density in your peripheral vision though, so you can't really tell whats outside of your central vision (fovea).

The flicker at 60 Hz is perceptible when looking at a pure white screen, but its hardly noticeable when looking at a game with any movement (try it).

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A game running at 30fps still feels choppy to me regardless of flickering. And 85hz is barely high enough to keep me from getting a headache from all the flickering. I'm very susceptible. I think I'd have a siezure if I used a monitor at 60hz for more than a few minutes.

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As Max_Payne said, I think that the only way to reduce the frame rate without too noticeable flickering is adding motion blur (it would increase the quality instead). Here in italy, the TV sends 25 frames/second and you don't notice any flickering (but perhaps the very low res has something to do with that).
Sadly, as far as I know motion blur is not free...

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Original post by cignox1
As Max_Payne said, I think that the only way to reduce the frame rate without too noticeable flickering is adding motion blur (it would increase the quality instead). Here in italy, the TV sends 25 frames/second and you don't notice any flickering (but perhaps the very low res has something to do with that).
Sadly, as far as I know motion blur is not free...


No, but it can be relatively cheap, especially if you're triple-buffering. Single full-screen quad rendered over the top of your backbuffer, textured with the contents of the previous backbuffer and lowered to 25% alpha or so. So it's an extra fill of every pixel on the screen; but relative to the rest of your scene that's probably not much.

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Original post by RAZORUNREAL
The only thing I can think of to trick the eye is update the screen in patterns, like you do every second pixel in a checker pattern. And that would look terrible if the rate was low enough that you could see what it was doing.


The tube in a CRT monitor works by updating every other line, so you might be onto something there. I'm not too sure how LCD monitors work though.

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