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> You can test this by looking at yourself in a mirror, focusing on one eye, then another. Do you see your eyes or face or anything blur? This isn't the best t

by sxp 3y ago

> You can test this by looking at yourself in a mirror, focusing on one eye, then another. Do you see your eyes or face or anything blur? This isn't the best test since your brain compensates for saccades by censoring input for a while. And it has built-in motion stabilization which allows you to read a sign while walking down the street. A better test would be to look at your finger or hand while waving it very quickly. You'll see motion blur as your finger moves. In certain cases, you can see individual "frames" as an afterimage. E.g, if you look at a modern car tail light, the LED isn't on consistently but uses PWM to blink really quickly. So if you move your eyes while looking at a tail light at night, you'll see a series of dots rather than a blurry image. Once you learn this trick, you can distinguish between analog lights and PWMs by noticing if they are blurry or discrete.

jvanderbot 3y ago
I'm more referring to FPS obsession with blurring things when the character moves, for that, turn your head quickly: Do you see a blurry room? I do not. Because your eyes must also move, and as you say, the brain censors because a "turn and look" includes an eye movement (I hypothesize). For fast moving things outside of ego motion, I can see a reason to use blur (e.g., your hand waving).
- SamBam 3y ago
  That's a good point, but how would turning your head in a first-person perspective ever look good in a game? As you say, when we turn our own heads our eyes naturally saccade. But I'm not sure having this done unnaturally -- e.g. by having a couple static intermediary images -- would look right at all. But smooth isn't right either.
  - jvanderbot 3y ago
    It would rely on the eye's natural saccade. My brain drops the intermediate frames already and I mostly just see the new perspective. just like real life. Adding blur makes the motion stand out.
    - SamBam 3y ago
      Except that your natural saccade is also wired to your motor neurons in your head and neck. For example, there's a strong connection between the neurons that fire to turn your head 10⁰ to the right, and the neurons that fire to turn your eyes 10⁰ to the left, which allows your eyes to fixate on something even as your head moves. Indeed, it's almost impossible to turn your head slowly without your eyes fixing on points in your field of view, and then saccading to the next point. Try it. This is a hard-wired response. (You can perform some tricks to do it, like completely blurring your eyes, but that's not really the point.) Meanwhile, if we watch a video with the camera turning, it's easy to keep our eyes staring straight ahead. This shows that there is going to be a difference between a head naturally turning and watching a video of a head turning. I think you're describing saccades as just being the "dropping out" of frames, and not including the extremely-relevant motion that our eyes do during a saccade.
      - jvanderbot 3y ago
        I appreciate the attention to detail in this thread. I think the only thing I can say here is - I dont see anything weird when I turn my head, and when FPS games added blur to "character moves his own body", it felt much less natural, not more. So, to answer question a few posts up "how would we do it?" I'd just say "The way we always have before we got enough GPU to make everything look like a movie"
        account42 3y ago
        > The way we always have before we got enough GPU to make everything look like a movie Actually I think motion blur is more of a (futile) attempt to hide low frame-rates because we don't have enough GPU to render the ever more demanding scenes.
  - account42 3y ago
    Just having a high frame-rate without (excessive) motion blur works pretty well. Perhaps it's not 100% realistic without eye movement but it's at least not as distracting as forced motion blur. I'm also not entirely sure that your eyes won't saccade in this case as they can lock onto moving objects just fine without body movement.
robertsdionne 3y ago
The point is that ego-motion-blur is dumb. (It can also make players motion-sick.) You say it yourself: "your brain compensates for saccades by censoring input for a while. And it has built-in motion stabilization which allows you to read a sign while walking down the street."
- robertsdionne 3y ago
  I think the best implementation (without eye-tracking) would not motion-blur the entire scene when the player moves themselves (ego-motion-blur) but would blur moving objects. However, if the player's view motion happens to coincide with the motion of objects in the scene, for instance if the player is tracking the object (maybe another player so they can shoot it in an FPS) then the object-motion-blur should be reduced according to the degree of tracking. I'm sure some game engines already do this.
devilbunny 3y ago
This was one of the interesting side effects of a small retinal hemorrhage. I had a fixed black spot (well, it actually looked a little like a thread) and the fact that it didn't move in my visual field made me realize just how many saccades you do.

by sxp 3y ago

jvanderbot 3y ago

I'm more referring to FPS obsession with blurring things when the character moves, for that, turn your head quickly: Do you see a blurry room? I do not. Because your eyes must also move, and as you say, the brain censors because a "turn and look" includes an eye movement (I hypothesize). For fast moving things outside of ego motion, I can see a reason to use blur (e.g., your hand waving).

SamBam 3y ago
That's a good point, but how would turning your head in a first-person perspective ever look good in a game? As you say, when we turn our own heads our eyes naturally saccade. But I'm not sure having this done unnaturally -- e.g. by having a couple static intermediary images -- would look right at all. But smooth isn't right either.
- jvanderbot 3y ago
  It would rely on the eye's natural saccade. My brain drops the intermediate frames already and I mostly just see the new perspective. just like real life. Adding blur makes the motion stand out.
  - SamBam 3y ago
    Except that your natural saccade is also wired to your motor neurons in your head and neck. For example, there's a strong connection between the neurons that fire to turn your head 10⁰ to the right, and the neurons that fire to turn your eyes 10⁰ to the left, which allows your eyes to fixate on something even as your head moves. Indeed, it's almost impossible to turn your head slowly without your eyes fixing on points in your field of view, and then saccading to the next point. Try it. This is a hard-wired response. (You can perform some tricks to do it, like completely blurring your eyes, but that's not really the point.) Meanwhile, if we watch a video with the camera turning, it's easy to keep our eyes staring straight ahead. This shows that there is going to be a difference between a head naturally turning and watching a video of a head turning. I think you're describing saccades as just being the "dropping out" of frames, and not including the extremely-relevant motion that our eyes do during a saccade.
    - jvanderbot 3y ago
      I appreciate the attention to detail in this thread. I think the only thing I can say here is - I dont see anything weird when I turn my head, and when FPS games added blur to "character moves his own body", it felt much less natural, not more. So, to answer question a few posts up "how would we do it?" I'd just say "The way we always have before we got enough GPU to make everything look like a movie"
      - account42 3y ago
        > The way we always have before we got enough GPU to make everything look like a movie Actually I think motion blur is more of a (futile) attempt to hide low frame-rates because we don't have enough GPU to render the ever more demanding scenes.
- account42 3y ago
  Just having a high frame-rate without (excessive) motion blur works pretty well. Perhaps it's not 100% realistic without eye movement but it's at least not as distracting as forced motion blur. I'm also not entirely sure that your eyes won't saccade in this case as they can lock onto moving objects just fine without body movement.

robertsdionne 3y ago

The point is that ego-motion-blur is dumb. (It can also make players motion-sick.) You say it yourself: "your brain compensates for saccades by censoring input for a while. And it has built-in motion stabilization which allows you to read a sign while walking down the street."

robertsdionne 3y ago
I think the best implementation (without eye-tracking) would not motion-blur the entire scene when the player moves themselves (ego-motion-blur) but would blur moving objects. However, if the player's view motion happens to coincide with the motion of objects in the scene, for instance if the player is tracking the object (maybe another player so they can shoot it in an FPS) then the object-motion-blur should be reduced according to the degree of tracking. I'm sure some game engines already do this.

devilbunny 3y ago

This was one of the interesting side effects of a small retinal hemorrhage. I had a fixed black spot (well, it actually looked a little like a thread) and the fact that it didn't move in my visual field made me realize just how many saccades you do.