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How to see in 3D without special glasses

Click here to skip to the short explanation.

There are many ways to see images in 3D. Most of them require you have special glasses like polarized lenses or red / blue glasses. However, one of the very best ways to see in 3D is a technique known as cross viewing.

A while back, 3D pictures of random dots became popular. To see these required parallel viewing. I personally found these very difficult to see and a lot of people just couldn't do it. Unlike parallel viewing, cross viewing is quite easy to learn. It also provides a large amount of depth, and has the advantage of being able to see full color images.

To start, lets talk about why we see in 3D in the first place. Look at something close to you. Now cover one eye, then the other. You notice the views of each of your eyes differs slightly. If you look at something far away, there is little or no difference between the views of each of your eyes. Your brain translates those differences into depth information.

Consider the image below. Which ball is largest? Which ball is closest? You can't tell. You can't tell because both of your eyes see the exact same image.

 a 2d image
The one thing all 3D viewing techniques have in common is they show each of your eyes a slightly different picture and your brain translates that into depth. Cool Huh?

OK, now hold a pencil a short distance in front of you and stare at the tip. Without taking your eyes off the tip of the pencil, notice what is in the background. If your computer monitor is behind the pencil you see two (blurry) computer monitors.

We see this all the time and we have just learned to ignore the nonsense in the background. However, I can use this to teach your eyes (brain) a new trick. Basically, it amounts to keeping your eyes 'crossed' like they are when you are looking at something close (like the pencil) but learning to focus on something farther away (like your computer screen).

Lets' do it!

Sit well back from your computer screen. After you learn to cross view, you can move closer but it's easiest to learn if you are at least 3 feet (a meter) away from your screen.
In a minute I am going to show you the same image I showed you earlier, only this time there will be two images side-by-side. I want you to hold your hands in front of you and arrange them so you see the image on the right side with your left eye and the image on the left side with your right eye.

left eye view

right eye view

There are two reasons for doing this. Not only are we showing each eye a different image, we are also blocking out the other image from the other eye. That helps when you are learning to do this. Later, when you are an expert, you won't need to do this.

Here we go! Now RELAX! This isn't going to be hard. In fact, the only hard part will be keeping your eyes from reverting back to the way you normally look at things. As soon as your brain locks into focusing on the computer screen there will be a tendency to uncross your eyes and you will lose the illusion.

Holding your hands in front of you as I have described, look at the place where your thumbs cross. That is, look at your hands, not at the screen. You want to level your head so the images are at the same height. Also, sit directly in front of your monitor. This is harder to do if you are at an angle.

Now this next part is a little hard to describe cause your brain just has to kind of do it. However, it will do it automatically (brains are cool like that). Without moving your eyes, pay attention to what is in the background. You have to merge the different eye views into a single picture and focus on the computer display but you will still have your eyes 'crossed' as if you are looking at the space where your thumbs cross.

A stereo image

Another way to do this is to hold a pencil about a foot (30 cm) in front of your face and stare at the tip. Notice you will see 4 images of the box in the background. Moving the pencil toward and away from you, try to get the middle two images to merge into one.

Did you see it? If you can do it, it will be obvious which ball is closest and which one is farthest way. Don't be discouraged if it is hard to hold the illusion. With a little practice you will be able to do it easily. Most people can use the pencil technique to cross view even if they only do it once in a while. If you do it often, you will be able to learn to just look at things that way.