4 ms·

I didn't realise how precise the reflections from retro-reflective materials were. I'd always just thought they were for high vis gear, cool to see such a creat

I didn't realise how precise the reflections from retro-reflective materials were. I'd always just thought they were for high vis gear, cool to see such a creative use for them here!

rkangel 5y ago
It's taken me a moment to think things through, but they only need to be precise enough to get back to the relevant user and not the one 90 degrees round the table. The precision that's important is the projector. You project the top left 'pixel' to the top left of the board, it retro reflects back in your general direction from the top left of the board. Same for bottom right and all the other pixels. I presume the better the retro-reflectivity the more efficient the system is (because less light is wasted going to places that aren't your eye), but it only needs to be 90 degree ish good enough for selectivity
- ajayyy 5y ago
  There is a different image per eye, so much more precise than that
  - PaulHoule 5y ago
    You don't need perfect separation to get a good stereo effect. My son bought a pack of red-blue 3d glasses and we were looking at anaglyphic images online and enjoying them even though the images weren't perfectly clean. In 3-d movies (Toy Story 3d) there are places where an isolated really bright object shows through cross channels and there some double imaging but it doesn't break the 3d. These work for most people https://en.wikipedia.org/wiki/Magic_Eye https://en.wikipedia.org/wiki/Magic_Eye and the channels aren't separated at all, your brain are doing it all out of desperation for closure. (Blood in the Gutter!)
    - aidenn0 5y ago
      Crosstalk can cause nausea and headaches in some people, just like VAC and motion lag. That being said, circular polarization off of a retro reflective screen is one of the two state of the art ways of doing step stereo 3d: if you saw Avatar in a modern theater, there's a good chance that was used, so crosstalk should be minimal and much better than with an anaglyph. [edit] I should also note that circular polarization is different from the linear polarization that was used e.g. in Disney attractions in the '90s (and thus still used in some of the older attractions). With linear polarization if you tilt your head 45 degrees to one side or the other you will get an even mix of the L/R channels in each eye. Circular polarization does not have that issue. Though it seems to me with the projector originating from the same plane as the glasses, circular polarization would be redundant. I'm sure the engineers there know more than someone who dropped out of physics after flunking the optics lab though :)
  - rkangel 5y ago
    If you read the article, the retro-reflectivity is not used to separate left and right eye images. Two different projections with different polarisations are done, and then filtered into the correct eyes. See the section "Left and Right Eye Stereo Polarization" under "A little of the physics".

I didn't realise how precise the reflections from retro-reflective materials were. I'd always just thought they were for high vis gear, cool to see such a creative use for them here!

rkangel 5y ago

It's taken me a moment to think things through, but they only need to be precise enough to get back to the relevant user and not the one 90 degrees round the table. The precision that's important is the projector. You project the top left 'pixel' to the top left of the board, it retro reflects back in your general direction from the top left of the board. Same for bottom right and all the other pixels. I presume the better the retro-reflectivity the more efficient the system is (because less light is wasted going to places that aren't your eye), but it only needs to be 90 degree ish good enough for selectivity

ajayyy 5y ago
There is a different image per eye, so much more precise than that
- PaulHoule 5y ago
  You don't need perfect separation to get a good stereo effect. My son bought a pack of red-blue 3d glasses and we were looking at anaglyphic images online and enjoying them even though the images weren't perfectly clean. In 3-d movies (Toy Story 3d) there are places where an isolated really bright object shows through cross channels and there some double imaging but it doesn't break the 3d. These work for most people https://en.wikipedia.org/wiki/Magic_Eye https://en.wikipedia.org/wiki/Magic_Eye and the channels aren't separated at all, your brain are doing it all out of desperation for closure. (Blood in the Gutter!)
  - aidenn0 5y ago
    Crosstalk can cause nausea and headaches in some people, just like VAC and motion lag. That being said, circular polarization off of a retro reflective screen is one of the two state of the art ways of doing step stereo 3d: if you saw Avatar in a modern theater, there's a good chance that was used, so crosstalk should be minimal and much better than with an anaglyph. [edit] I should also note that circular polarization is different from the linear polarization that was used e.g. in Disney attractions in the '90s (and thus still used in some of the older attractions). With linear polarization if you tilt your head 45 degrees to one side or the other you will get an even mix of the L/R channels in each eye. Circular polarization does not have that issue. Though it seems to me with the projector originating from the same plane as the glasses, circular polarization would be redundant. I'm sure the engineers there know more than someone who dropped out of physics after flunking the optics lab though :)
- rkangel 5y ago
  If you read the article, the retro-reflectivity is not used to separate left and right eye images. Two different projections with different polarisations are done, and then filtered into the correct eyes. See the section "Left and Right Eye Stereo Polarization" under "A little of the physics".