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> there's no way to make things darker https://en.wikipedia.org/wiki/Liquid-crystal_display#Twisted_nematic_.28TN.29 https://en.wikipedia.org/wiki/Liquid-cryst

> there's no way to make things darker https://en.wikipedia.org/wiki/Liquid-crystal_display#Twisted_nematic_.28TN.29 https://en.wikipedia.org/wiki/Liquid-crystal_display#Twisted...

sillysaurus3 9y ago
I thought so too, but unfortunately this doesn't work either. The reason it won't work is the same reason scratches on your eyeglasses don't appear sharp. Your focus is in the distance, so you won't see whatever dimming has been applied Not unless you use it to darken e.g. an entire quadrant of your lenses. Interestingly, this problem applies to text rendering too. It seems unlikely that you'll be able to project clearly readable text over anything when it's an inch away from your eye.
- jon_richards 9y ago
  Can you elaborate? Isn't the basis behind VR that you can show different images to each eye to trick people into thinking they are looking at something far away? Is there something about the cornea/lens shape that prevents this from working with AR?
  - sillysaurus3 9y ago
    Yeah, so the reason VR works is that it controls the entire scene. The light being projected towards your eyes is from a consistent focal plane -- the light comes from a flat surface located exactly N inches away from your eyes. That means you can focus sharply on it. AR is a very different beast. In the real world, your focus is usually several feet away, or sometimes across the room. Your focus also changes almost instantly. Yet AR still needs to project light toward your eye from exactly N inches away. You can simulate this: Find some glasses and put some black tape over part of the lens. You'll notice the tape doesn't appear sharp and crisp. It's a blur. (Or just close one eye and put a finger close to your other, and look out in the distance.) I'm not sure AR has any hope of rendering text in a readable way. It'd be like writing some letters on your finger, then putting it up to your eye while looking out in the distance. Even if the letters glow, so that they're a light source, you still can't read it at all.
    - jon_richards 9y ago
      I didn't think your explanation could be right, since VR headsets are very close to your eyes. Try closing one eye and putting a finger close to the other. You can't see it in focus even if you don't look out in the distance. The bit I was missing is that VR headsets use lenses to adjust the angle of the incoming image to simulate the image being farther away (this is completely different from the depth perception created by sending different images to each eye). This video is a great explanation: https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ This does make AR much more difficult, since a lens that adjusts the simulated image would also adjust the real image behind it, but I don't think it makes it impossible. There may be a way to simulate a Fresnel lens just for the simulated image or use miniature one-way mirrors to do so. Edit: I think hololens actually accomplishes this, but its very complicated: http://www.imaginativeuniversal.com/blog/2015/10/18/how-hololens-displays-work/ http://www.imaginativeuniversal.com/blog/2015/10/18/how-holo...

> there's no way to make things darker https://en.wikipedia.org/wiki/Liquid-crystal_display#Twisted_nematic_.28TN.29 https://en.wikipedia.org/wiki/Liquid-crystal_display#Twisted...

sillysaurus3 9y ago

I thought so too, but unfortunately this doesn't work either. The reason it won't work is the same reason scratches on your eyeglasses don't appear sharp. Your focus is in the distance, so you won't see whatever dimming has been applied Not unless you use it to darken e.g. an entire quadrant of your lenses. Interestingly, this problem applies to text rendering too. It seems unlikely that you'll be able to project clearly readable text over anything when it's an inch away from your eye.

jon_richards 9y ago
Can you elaborate? Isn't the basis behind VR that you can show different images to each eye to trick people into thinking they are looking at something far away? Is there something about the cornea/lens shape that prevents this from working with AR?
- sillysaurus3 9y ago
  Yeah, so the reason VR works is that it controls the entire scene. The light being projected towards your eyes is from a consistent focal plane -- the light comes from a flat surface located exactly N inches away from your eyes. That means you can focus sharply on it. AR is a very different beast. In the real world, your focus is usually several feet away, or sometimes across the room. Your focus also changes almost instantly. Yet AR still needs to project light toward your eye from exactly N inches away. You can simulate this: Find some glasses and put some black tape over part of the lens. You'll notice the tape doesn't appear sharp and crisp. It's a blur. (Or just close one eye and put a finger close to your other, and look out in the distance.) I'm not sure AR has any hope of rendering text in a readable way. It'd be like writing some letters on your finger, then putting it up to your eye while looking out in the distance. Even if the letters glow, so that they're a light source, you still can't read it at all.
  - jon_richards 9y ago
    I didn't think your explanation could be right, since VR headsets are very close to your eyes. Try closing one eye and putting a finger close to the other. You can't see it in focus even if you don't look out in the distance. The bit I was missing is that VR headsets use lenses to adjust the angle of the incoming image to simulate the image being farther away (this is completely different from the depth perception created by sending different images to each eye). This video is a great explanation: https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ This does make AR much more difficult, since a lens that adjusts the simulated image would also adjust the real image behind it, but I don't think it makes it impossible. There may be a way to simulate a Fresnel lens just for the simulated image or use miniature one-way mirrors to do so. Edit: I think hololens actually accomplishes this, but its very complicated: http://www.imaginativeuniversal.com/blog/2015/10/18/how-hololens-displays-work/ http://www.imaginativeuniversal.com/blog/2015/10/18/how-holo...