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Anaglyph / 3D stereo on normal monitors without red-cyan glasses?


Mircea Lobo
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So this is the story: I play several games apart from Second Life (usually FOSS ones which new features can be easily added to) and have recently been interested in 3D image / visual stereo. Most support red + cyan anaglyph and until now I used that with my 3D glasses. But as everyone knows, this washes the colors out while using such glasses for too long tires my eyes. I only have a normal LCD monitor and am not looking to get a special video card / monitor / video drivers for this... just achieve it with existing hardware (apart from the necessary glasses). I've been googling about this, and most people say red-cyan anaglyph is the one and only way with normal monitors.

I have however seen something that might work, and wanted to ask if anyone else has done it and what exactly must be used to achieve it. Second idea is something I've come up with, and wanted to ask if it's possible and being done too. Let me know what you think, and also if you know of another way to get 3D working on a normal monitor (if there is any after all).

- Idea 1:

I read about active and passive 3D glasses. Active ones require electricity to shut the lenses in sync with the screen, and cost a lot while requiring a special monitor, so no. Passive ones normally need a special monitor too, but the hack I heard of gets rid of this requirement. What I read is that by using a certain type of plastic foil you can invert the polarization of any LCD / LED screen. If done properly, covering half of the screen with a type of foil while covering the other half with the same foil but flipped would make one lens of the polarized glasses see one half of the screen and the other lens to see the other half. Some games allow side-by-side 3D, so if I could make each eye see only one side it might actually work.

The problem with this is that for red-cyan anaglyph, both channels overlap on the whole surface of the screen. Hiding half of the screen for each eye might cause eye strain... if it's even possible at all without causing eye damage. Physically speaking, each eye needs to look in the same spot (otherwise you go derp), so I have no idea if both eyes looking at the center of the screen like this would still connect the images in the brain. The proper solution would be separating each picture / camera via refresh rate (one every line / pixel) but this gets into requiring special hardware. I only saw a video about this method, and would like more information.



- Idea 2:

Additionally, there is another idea I thought of that could be used to put an image on each eye with a normal monitor. Instead of separating by colors (eg: red and cyan) separate by brightness ranges. In this case, another pair of special glasses would be needed (which I doubt even exists); One where the left lens allows a brightness between black and a given level of gray, while the other filters brightness between the same level of gray and white. The 3D renderer would then divide each image / camera as follows: The image for the left eye would be darkened / scaled so that the brightest white becomes 50% gray (pure black remains unchanged) while the image for the right eye would be brightened / scaled so that the darkest black becomes 50% gray (pure white remains unchanged). Both eyes connecting the images should then achieve a normal brightness back to some extent.

I'm not sure how overlapping those over the same area of the screen would work, and it would surely be annoying for each eye to see a different brightness level. Still, if this would work out it would allow visual stereo on a non-3D monitor without messing up colors. Are there any glasses that can filter by light intensity, and is this an usable alternative to red-cyan stereo?

 

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Polarised glasses, with the polarisation of each eye turned 90 degrees to the other, have been the standard 3-D method in cinemas for many years. I don't know when coloured glasses were last used - probably in the 50s or 60s. Since the method is used in cinemas, I don't see why they can't be used with monitors. Monitors use pixels which cinema screens don't, but the pixels are so small that I'm sure the polarised method can be used.

 

Interesting thing to do:-

Get a pair of cheap polarised sunglasses. Pop the polarised plastic eyepieces out of them. Get some clear cellophane, such as the clear cellophane outer wrapping of a cigarette packet. Crumple it a lot. Put it between the 2 eyepieces and look at it through the front eyepiece. Now rotate one of the eyepieces slowly while still looking through eyepiece 1, crumpled cellophane, eyepiece 2. You'll like it.

Better still, get a small sheet of clear glass or plastic and some cellophane sticky tape (it must be cellophane (cellulose)). Stick some short lengths of the tape flat on the glass, at various angles, so that there are many overlaps. Put one of the eyepieces behind it and look through the other eyepiece in front of it. Then rotate one of eyepieces slowly. You'll like it even more - and you'll be amazed.

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Some nice news on this: I managed to see stereo without glasses today, by using side-by-side / horizontally split viewing in a game that has this feature. Looks really neat... and by using polarized glasses + cellophane to hide halves of the screen from each eye, you don't see the other two "screens" either. I managed to do this in fullscreen and could even get as close as I normally do to the monitor without the combined image breaking apart.

However, it's very tiring for the eyes, and I'm not sure if it could even cause eye damage. After doing it for just a little my eyes were slightly hurting, and for a few minutes I had a hard time properly focusing them in real life (felt like they were focusing off). So I don't recommend doing it... at least not for long periods of time. The proper way is managing to put both channels over the same surface of the screen, but that remains a very hard task with normal hardware.

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Quite a long time ago, one of the British TV companies showed a specially-made 30 minute Dr. Who episode in 3-D and without the need for viewers to wear any sort of glasses. It worked! It really did. And it still worked when watching a VHS recording of it. I have no idea how it was done but it did have a major drawback. The 3-D effect only worked when the camera was moving. For instance, I remember a bit where Dr. Who was talking with someone on a street corner and the camera was moving round and round them as they talked. That bit was what made me notice that the camera needed to be moving.

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Whatever trick they used, I never conceived of a way it could be done. It was back in the days of CRT TVs and it was *really* good - as long as the camera was moving.

I haven't seen it anywhere since it was shown back in the 90s, but you could try a YouTube search on "Doctor  Who 3-D".

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