Discovered Maxwell's Spot illusion while looking further into this https://www.psy.ritsumei.ac.jp/akitaoka/Maxwell_spot_illusio...
This is a flickering blue/green image. In the center wherever your eyes are looking, you will see a dark spot.
Fascinating. I get very different results depending on which glasses I use.
I'm far-sighted with a relatively weak prescription.
Without glasses I have a tiny bit of lazy eye, it's not really perceptible for the most part looking at me, but for stuff like this I get a sort of figure-eight shaped blob of motion that skips around a fair bit which I guess is because my eyes fail to track correctly and can't find anything to focus on. Can't perceive the motion outside of this area.
With my regular glasses this there's still some of this effect, but much less pronounced. Can't see any motion outside of the center of my field of view.
With my reading/screen glasses, which technically makes me myopic, I get a large perfect circle, and can still detect a lot of motion outside of the circle, even if it's "low FPS".
The strength of the glasses alters the size of the image that lands on your retinas. More (-) means a smaller image thus you stop seeing movement much closer to the focal point.
Shadertoy got hugged to death by this shader a few years ago and it had a custom "please go away" banner for a little while. Funny seeing it show up again on HN front page.
https://web.archive.org/web/20210430091013/https://www.shade...
That's pretty cute. IQ's a good guy, he's had every opportunity over the years to monetize Shadertoy but it's stayed free and true to its purpose for 12y now.
it's too bad we associate paying people for their work with not being a good guy
Keeping a site free for others to learn and share art is being a good guy.
Too bad that we associate monetizing a demoscene site with getting paid for your work.
Hi, I don't know what this is supposed to do, but I get pretty bad migraines and loading the page made me feel extremely strange almost immediately so I closed it.
I would check to make sure this can't trigger migraines or seizures. Maybe it's just me, but also, please double check.
I don't usually have headache migraines but do have strong visual auras from time to time.
Looking at this it first looked fun: "whoa, that's cool, this fovea thing is really smaller than I imagined"
After a minute or so playing around I closed the window and then I noticed a form of retina persistence that looked eerily similar to an onset of a visual aura, as well as some faint but clear ear ringing, both typical symptoms of the migraines I experience.
I immediately walked away from the computer and although dwindling it's still in effect 10min out.
Yes. Occasional migraine sufferer with aura here. Don't look at this unless you want to spend the next 15 minutes worrying "am i getting an aura or not".
How would someone possibly “check” that? What method are you proposing?
there are a lot of papers on this (some made by inducing seizures in people under lab conditions). The most seizure causing things you could display are simply bars or a grid with moving details, sizes, or alternating in colors.
Basically if it gives you a headache to stare at or just has this sucky attention grabbing feel to it when you look at it its likely to cause seizures. I CBA to dig up the papers on this but there are a bunch if you want to really get into this.
You should be arsed to dig it up because your parent comment is insinuating disbelief or sarcasm with quotation marks.
Here is the study that came to mind: https://www.cell.com/current-biology/fulltext/S0960-9822(17)...
However as the above study iirc doesn't directly state that these patterns cause discomfort and doesn't contain any examples I suggest reading chapter 10 "Photosensitive Epilepsy and Visual Discomfort" of "hierarchies in neurology (1989)" on page 70-71 which proposes this AND contains an example you can look at yourself.
Its supposed to show you how big of a radius your eye can focus on at a time, as we age the radius shrinks.
Edit: seems like there isn't enough research to suggest the latter. Apologies
Yes, immediately felt weird and a bit uncomfortable. I can almost see, or kind of sense, all those parts moving in the image even though I can only see the movement clearly in the center. I can easily imagine getting a headache from watching that for a longer time.
Interesting, I wonder.. have you ever tried a VR headset? Does that cause you migraines as well? or maybe any other discomfort that'd prevent you from using it?
Not op but, VR is no problem, but this microsoft ar/mr glasses gave me an instant crazy headache in places I did not even know I had matter (back of the head), apparently thats the visual processing part of your brain. Terrible experience that lasted an hour or so.
I don't know why you got downvoted. This seems like a very useful contribution.
I also don’t think it is downvote worthy.
The first part of the comment is very valuable. “I looked at it and it made me feel extremely strange almost immediately“. That is very good to know.
The second bit I’m less sure about. What do they mean by “check to make sure this can't trigger migraines or seizures”? Like what check are they expecting? Literature research? Or experiments? The word “check” makes it sound as if they think this is some easy to do thung, like how you could “double check” the spelling of a word using a dictionary.
I interpreted it loosely, as "be aware of the possibility, and stop looking at it at the first signs of issues".
That seems to me to be a VERY generous interpretation of:
> I would check to make sure this can't trigger migraines or seizures. Maybe it's just me, but also, please double check.
It's important to point out that all of the crosses are rotating, so this is effectively showing which parts of your vision are susceptible to change blindness (which is effectively 99% of it).
A fully psychometric version of this that explores more than just the fovea could be created by varying the scale parameter (if you crank it up high enough you can see the movement in the periphery). The additional component you would need is to have trials where the subjects has to report whether a particular region (could even be cued with a red circle, I don't think it needs to be random) is actually moving or not while fixated on the center. There are clearly cells that detect this kind of motion in the periphery but they need larger visual input, possibly because the receptive fields of the cells that feed in are larger out there.
Hah, so my comment here spawned a post: https://news.ycombinator.com/item?id=45904434
Yup :)
I first thought the spinning was an optical illusion, like https://www.nationalgeographic.com/science/article/how-our-b.... But in this case the spinning is real and you don’t see the rotation except in a small area (your fovea).
woah its incredible how quickly i can spot the fuzzy spot around where i can clearly see the rotation, and when i unfocus can see fuzzy movement all around. This is really cool. So this is the theory beind foveated rendering/streaming
The site is unavailable, because it is infected with cloudflare.
Seem iquilezles has finally given in. He's been complaining about crawler attacks a lot in the last months/years.
https://x.com/iquilezles/status/1977172864785957340 https://x.com/iquilezles/status/1976866381099679817 https://x.com/iquilezles/status/1838858759336267842
How can you have problems hosting a website that is so obviously cacheable.
.... Which is why he used cloudflare. Caching isn't magic.
How strange; it worked on my machine. Is your network incompatible with Cloudflare?
I wish there was an url parameter to share this fullscreen right away!
UPDATE: And yep, there (mostly) is! https://www.shadertoy.com/embed/4dsXzM?gui=false&paused=fals...
At the default scale of 90, I can't see anything spinning at all even with the video full screen. If I set the scale to 250 or larger I can see the stars spinning, but I just see the whole field spinning. Even if I get so close to the screen it almost fills my field of vision.
So for me either the stars are too small to see any motion, or I can see them all spinning no matter what.
What effect am I supposed to see?
If I set the scale value (150) to roughly the ppi of my screen (4k 27"), I can see the effect. You should see the rotating stars only in a small field of view (fov) where your eyes are focused and all other stars should seem to remain still.
My phone screen is a bit over 500 ppi. I tried it full screen across the entire range that it's in focus (I'm mildly nearsighted), and I could just see the things spinning across the whole field if the pinwheels were big enough to see motion at all.
Maybe it doesn't work on small/AMOLED screens?
Try it in full screen, if you did not.
> What effect am I supposed to see?
I can see only a tiny area in the center of my vision animate (at default scale). The larger the scale, the bigger the area.
Does anyone know how the hell this works
Most of what you think you are seeing at any moment is only imagined.
The retina is not uniform. Most photosensitive cells (cones) are near the centre of vision. Peripheral vision has little resolving power. Can't make out fine details. The reality of this is much more extreme than it subjectively feels like. The eye doesn't actually have pixels but if it did they'd all be focused at the centre. Like an image where 10% of the area in the middle had 80% of the pixels.
At the centre of vision the eye has enough resolving power to make out the tiny star shapes and see that they are rotating. Outside of that narrow zone in the peripheral vision they're perceived as coloured blobs, at best. Normally your brain would make this transparent to you. But this is an unusual pattern. Your visual cortex doesn't realize all the stars should be rotating. So only the ones you can actually see at any one instant seem to rotate.
Try to look at an object in the room with you, such as a lamp, without looking at it directly. Observe it out of the corner of your eye. The more you try, the less sharply defined it will seem. At the very edge of your vision you're only getting a handful of pixels worth of colour information. But because you know it is a lamp, it has the sharpness of a lamp's definition even though you cannot actually see that definition without directly looking at it. That's a related illusion.
This is why the eye scans constantly in those micro-jerking motions known as saccades. If a face were to pop up on your display, it would feel like a single instant recognition of a person. But before you experience that the eye would scan over the eyes, mouth, nose and so on, several times, in sharp flicking motions, over about 100 milliseconds, and these dozen or so little snapshots, as it were, would be stitched together into the whole image of a face. Even though only a tiny slice of the eye, or the nose, etc. can actually be seen at any one time, you perceive the whole face.
This illusion hacks that and reveals how narrow our high-resolution vision really is. The whole visual field feels rather high resolution. But only that tiny spot where they rotate actually is.
> Most of what you think you are seeing at any moment is only imagined
For some great illustrations of this I recommend people take a look at the Nova episode "Your Brain: Perception Deception" [1]. Nova episodes usually are only available to watch for free for a couple months after they air, then you have to be a PBS contributor, but occasionally old episodes become temporarily available. This one happens to be available now, with the video embedded at the link I gave.
The whole thing is worth watching, but for the material most directly relevant to this you can start at the 7:13 minute mark, where it briefly discusses a well known optical illusion and why it works, and then looks at the question of if you brain can fake your perception so much to make that illusion work, just how much of what you see in normal scenes is real? Then they go into how you only have about 1 degree of high resolution vision at the center.
A couple minutes after that there is a demo showing an interesting way to exploit that. They put the host in an eye tracker that can figure out where she is looking. Then they have her read some text on a monitor and she has no trouble reading. But when the camera shows us the monitor we see that almost the text is just the letter 'X' with small groups of letters briefly switching to other letters and then going back to 'X'.
When we read our eyes don't smoothly scan the text. They actually look at a fixed point for a moment, then jump to another fixed point, and so on (the "saccades" mentioned in the above comment). This isn't just when reading. This is how we look at everything.
She can read the text because the eye tracker is figuring out where she is looking a the software shows the real text there. As soon as her eyes jump that text goes back to 'X'.
When we look at the text and aren't looking exactly where she is we might detect the change to normal text where she is looking but we can't read it because most of the time it will be outside of the small high resolution center of our vision. By the time we can move our eyes down to it her eyes have jumped and that text is back to 'X'.
We don't consciously control the jumps so we can't sync ours to hers, so at best all we can hope for is to occasionally get lucky and maybe get a couple words now and then.
[1] https://www.pbs.org/wgbh/nova/video/your-brain-perception-de...
We're sorry, but this video is not available.
:(
It's also interesting to look at the second hand of a stopped watch to see the opposite effect.
Is it a problem if the shape that I see rising stars in is not round? I get an upside down L shaped mass of rotating stars, no matter where I look in the image.
For me it's an L shaped blob as well. Not circular at all.
I get some slightly rotated pear shaped thingy but also varies with where I'm looking at. Crazy!
It's like an upside down egg for me.
You can see everything in your field of vision, but the area DIRECTLY in the centre has the highest level of detail. This image has high frequency animated details that are not cognisized equally by your entire FOV. The animated bit right in the middle at any given time is where your brain processes the most detail and also where you are looking.
I had to think about it, but are you saying all the stars are animated to rotate, but the amount they move between frames is too small for you to see unless it's in your fovea?
They're just so small that you only see shapeless blur outside your fovea. If you applied an artificial blur filter to the whole screen, you'd also not see any movement anymore because all high-resolution detail is removed. A 3x3 box blur will erase differences between
X X X X and X X X X XThey are tiny and the ones not on your fovea don't register enough "pixels" for your brain to recognise the rotation.
Oh cool so it’s about the frequency?
Spatial frequency, ie. small detailed things, not temporal frequency (in this example).
The links seems to be down. From what I gathered, this is its video https://www.youtube.com/watch?v=3RUcQV3rd9k
What kind of sorcery is this? Incredible visualization!
The idea is to look at the scene and observe which crosses are rotating. You will notice that in your peripheral, the crosses appear not to rotate (although they are, and you can check that by focusing on them). This gives you an idea of how large your fovea is.
On a retina Mac I had to double the scale value to get reasonable results.
Oh wow, this made me realize something I've had for 20 years: When I look too close for a few seconds, I get blurriness at the center of my vision. It goes away after a while, but this made me realize that the blurry region is actually my fovea!
I have no idea why my fovea blurs when I look close up at something, and doctors haven't been able to figure it out, but at least now I can google it better.
That reminds me of myself as a kid looking at the moon and losing focus after just a few seconds. I could never figure it out.
I can't see any movement, at any distance. How likely is it something weird with my vision vs. something weird with my monitor/computer? I'm on a 360hz monitor at 2k.
The sizing and distance to you your face is important so you can play with that and change #define scale at the top.
I have nystagmus (rapid, uncontrollable, rhythmic eye movements), so I couldn't see anything at first, just lots of small dots.
I had to zoom in (Mac accessibility tool) but then I could see the effect briefly. My eyes go everywhere, but I could see patches of moving shapes with stationary shapes further away, only that the patch moved around a lot!
does your brain just give up when the little stars seem to be still until you focus on one/a few
oh I see fovea
This is a truly incredible demo.
Way cooler than the title suggest. I nearly didn't click.
Awesome. You'll see the little stars rotating only in the area they reach your fovea, the most sensible part of the retina. All the rest will not be able to perceive any motion.
I get about 4cm wide at 50cm distance.
This would make for a cute screensaver
I don't get it, all I see is:
"Bad request"
am I missing the joke?
No, there should be a shader (think video) rendered showing a bunch of tiny spinning things. Something went wrong when you tried to load the page. It's an optical illusion where only things close to the centre of your vision look like they are spinning and everything else looks still.
Okay, thanks.
ok, i dont get it.
on my phone at typical distance and 90 scale i only see about an asprin tablet size area spinning. but at 180 scale i see almost everything spinning at same distance.
i think peripheral vision is quite sensitive to movement/contrast changes, but the moving shapes have to be large enough to trigger those receptors?
not sure what to conclude from this.
What’s the correct scale for 210dpi?
You can also increase the "lengt". Doubling it works well on my Macbook, and the pattern is more dense so you can see your fovea better.
It depends on viewing distance as well.
180 worked pretty well on my Framework 16.
Ditto on my MacBook Air
This is quite cool, rocked back and forth from and to my screen and got a (bit inconsistent, but consistently visible) "shape" of the fovea. maybe 30% larger than I thought it'd be!
Right after though, I felt like my vision was clouded, like there was a grey overlay on it or something for a few minutes. Don't recommend having this open for too long. Visual cortex doesn't like running against its limits I guess
Amazing - but iPhone screen is too small. Works on my iPad.
That's due to the retina display. Try fovea.
Just zoom in a bit
Worked on my iPhone
Reminds me of this app that is supposed to clear up your brain when staring at the screen for a while
>clear up your brain
Just to be clear, we don't actually know what that does right? Like, there's no link to this making up for poor sleep or improving your cognitive function right?
Babies would go nuts over this, so much contrast and movement
This actually does work!!
How do you know?
Feels like a gentle rub on the skull from inside, and the overall feeling is akin to that of a lucid dream, but with a bit of nausea. Not too pronounced of course, but detectable.
TL;DR it helps you identify the true diameter of your visual focus, which is said to shrink with old age (mine shrinks more in terms of _time_ dimension but that's a different issue!)
For best results, use it _fullscreen_, change the #define `90` values to a higher value if you're on a high dpi screen.
Stare at a few places on the screen and you'll get the effect of appearing to rotate only where you stare.
It's pretty neat.
