There are two main types of 3D images viewable without viewers or special glasses. Both trick your brain into seeing two 2D images with one 3D image between them. One viewing method is the "Straight" or "Parallel View", the other; "Cross-eyed".
"Parallel" or "Straight" view 3D images.
In this method, your left eye sees the left image and your right eye sees the right image. Your focal point is far distant, and if you have a reflective screen, this can greatly help viewing/resolving these images. With the image on the screen, focus on some image behind you reflected off the screen. A light, the ceiling, etc., then gradually try to see the image on the screen with your peripheral vision. It takes a few second for your brain to realize the image makes sense, then it will resolve and you can focus on it. The reflection will seem to fade as the center picture becomes clear/resolves to your brain.
The two red dots at the bottom of the image should be three red dots now, and the center pic should look 3D.
Without a reflective screen you'll either have to look over the top of the screen at something across the room (easier with a laptop, of course) and catch the screen image peripherally, or just try and relax your eyes while looking at the red focus dots. Let the two dots blur into four. The two dots in the center will wander toward each other. Let them if you can. When they merge into one dot, the image should resolve clearly. This does take some practice...
This method, for me, seems to be a bit easier on the eyes, BUT, the limitation with "Straight" or "parallel" 3D images, is that the corresponding portions of each image can't be wider than the distance between your pupils. This limits the size of the picture you can view. Which brings us to the other type of viewerless 3D image:The "Cross-eyed" 3D image.
It's much easier for the average person to cross their eyes than make them "goggle" (face apart). The cross-eyed method relies on this, and since you can cross your eyes -a lot- if you want to, the image size can be pretty large. In cross eye viewing the image for the left eye is on the right and the image for the right eye is on the left. To easily view cross-eyed 3D images, hold your finger about 6-10 inches from your nose and focus on the tip. The image should be on your monitor, behind your finger, a couple feet.
As you focus on the tip of your finger, move it toward or away from your face until you see three distict images on your monitor. Try to shift your focus from your finger tip to the 3D image in the center. It takes a few tries, but once you've done it a few times, you won't need your finger as a focusing crutch.
If you can't make it work, no big deal. A lot of people can't. Don't give yourself eyestrain trying to force the images to resolve. Most of the 3D images on this site will be cross-eyed images and linked to larger versions. Those that aren't will be labelled and have red focus dots on the bottom.
