I remember as a kid when I went to a 3D movie and you would have to wear those glasses with one blue eye and one red. Then a couple years later, you don’t need those red/blue glasses but these clear ones. And now you don’t need glasses at all.
Why is that?
In: 9
When you look at something in real life, because there is a distance between your eyes they recieve slightly different images. Your brain patches them together in a way which allows you to “see depth”.
If you want to see something in 3d being projected from a 2d screen, you need to make your eyes recieve distinct images that “capture” the depth, albeit in an artificial way.
Coloured glasses did this by basically showing a blue and a red image on top of each other, each corresponding to what each eye would “see”. The coloured glasses just filter one image each, so you get distinct images in each eye.
More modern 3d movies use polarisation instead of colour. Basically (and this is not exact, rather ELI5) the image that they want your right eye to see vibrates up and down, the image for your left eye vibrates left and right. The right lens has a grating that vertically, so the left-right vibrating image gets blocked but the up-down image passes through, and vice versa in the other eye.
I’m not sure how glassesless 3d works, I know of some prototypes that used gratings slightly offset from the original image, so the light that passes through is different depending on where you view it from, I think the Nintendo 3ds used this. The big problem is you have little flexibility in viewing angle.
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