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

So this is the story: I play several games apart from Xonotic (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. Xonotic allows 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?

Idea 1: Your left/right images would still be physically separated. That means you'll have to do parallel or cross-eyed viewing, which is already possible without any sort of polarization filter and glasses, is supported by Darkplaces, but is very straining on the eyes.

Idea 2: Not possible. You'd lose half of the dynamic range because of the compression (ugliness!). Also, that's not really physically possible either. You would need fine calibration to make this work (otherwise the left eye's brights would overflow and become right eye blacks and the other way around if you don't have screen-wide fine-tuning).

Not to mention that I really don't see how you expect to superimpose the two images on a single screen. A gray level is typically encoded in 8 bits (0-255), you're proposing to encode 7 bits of info for the left eye (0-127) and 7 bits of info for the right eye (128-255), which means displaying 14 bits of info in a single gray level. That's more than the 8 bits used by a full-range gray level. If you want to encode two compressed gray levels in a single one in a separable way, you need to take the square root of the original range's width. That means 0-15. And it wouldn't be as simple as filtering past a threshold to separate the two.

OR: you could interleave the two images and waste half of your resolution AND half of your dynamic range. But such glasses aren't possible anyway.

The only decent way I see to have 3d on a normal computer screen is through a system of mirrors that lets the eyes each see one half of the screen while in a natural position so to not induce pain after a few minutes. I'm sure this has been done before.

Yeah, I know that if using either of those methods you lose quality greatly one way or another. But I imagine that's the best that can be done with normal hardware, so cutting either the resolution or bit depth to half would seem acceptable.

As for idea 2, yeah... first of all you'd need glasses that can filter by level of brightness, but when the two images overlap they would cause intermediary shades of gray so it would all be a mess instead. The images would still need to be separated by lines / pixels and that would probably require a different monitor and you'd also lose resolution here.

I checked the side-by-side feature in DP, but without special glasses I only see two images (no way for my eyes to combine them). Is it actually possible to look at the screen split in two and see the images combined? Do you need to sit at a special distance for it?

I can do cross-eyed viewing and have been able to do parallel too. It's harder for larger images because your eyes need to be forced further. Increasing the distance to the screen helps, but fullscreen wouldn't be possible for me.

I suggest you look this up in a search engine or something. But don't try too hard, it can get painful and tiring.

I suggest you look this up in a search engine or something. But don't try too hard, it can get painful and tiring.

I think your problem is that you're still using Yahoo.

Some nice news on this: I managed to see stereo without glasses today, by using r_stereo_horizontal (side by side viewing). 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.

That's exactly what 3d polarized screens are for, and you're trying to reinvent that.

Could you show us a film of you doing it MK?

That would be awesome.

A film of what? Him cross-eyed with polarized glasses?

His setup. A film of his screen.

That's exactly what 3d polarized screens are for, and you're trying to reinvent that.

Polarized screens have one major difference: They divide each image between pixel lines (it's called interlaced or interleaved stereo IIRC). There's no eye strain then because both images are over the same surface. Side by side is different, and what I'm doing only works with that.

Could you show us a film of you doing it MK?

That would be awesome.

No, but I can show a picture of me using cellophane to filter with the glasses.

That's exactly what 3d polarized screens are for, and you're trying to reinvent that.

Polarized screens have one major difference: They divide each image between pixel lines (it's called interlaced or interleaved stereo IIRC). There's no eye strain then because both images are over the same surface. Side by side is different, and what I'm doing only works with that.

Sure thing, I was actually refering to this part of your message:

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.

My bad for not explicitly quoting it.

As for the picture, rotating your glasses 90 degrees inverts the visibility of both halves for each eye, right? I see the left eye sees the right half with the glasses rotated, so does that mean you're using parallel viewing?

As for the picture, rotating your glasses 90 degrees inverts the visibility of both halves for each eye, right? I see the left eye sees the right half with the glasses rotated, so does that mean you're using parallel viewing?

Cross viewing (as that's also the only way the eyes focus it for me). Left side is hidden from the left eye, and right side is hidden from the right eye. But the glasses + cellophane are just helpers, I can do it without blocking a side from an eye (but it's more distracting then since I see two additional unfocused images behind).

Don't the sides switch if you rotate the glasses 90 degrees though? Or is this actually circular polarization? I think that might be it, the cellophane serving as a quarter wave plate.

EDIT: See: https://en.wikipedia.org/wiki/Polarizer#...polarizers

Don't the sides switch if you rotate the glasses 90 degrees though? Or is this actually circular polarization? I think that might be it, the cellophane serving as a quarter wave plate.

EDIT: See: https://en.wikipedia.org/wiki/Polarizer#...polarizers

Yes, circular. Said so on the glasses when I bought them, and TBH I prefer circular because the image doesn't appear / disappear as you move your head around. If I look through the glasses the other way around, then it no longer hides anything.