3D picture, 3D Stereograms or 3D optical illusions
>>The picture above should be viewed widened (landscape)<<
Title: DANCING DOME ~ NEW
Look at the two red marks above the picture. Diverge your eyes as though you are looking through the image into the distance. Diverge your focus into the distance until you see two squares above the image turn into three squares.
When you clearly see three squares, at that distance the hidden 3D image will magically appear. Once you perceive the hidden image and depth, you can look around the entire 3D image easily. The longer you look, the clearer the illusion becomes.
The main trick to seeing stereograms is learning to de-couple your focus and eye positioning.
Some people who wear glasses will find it easier to if they take them off as long as they can move close enough to the image to see it clearly.
Look straight on, don’t twist your head. The 3D illusion is most apparent with your head level.
Be relaxed and give it some time.
Get very close to the stereogram, and very, very slowly pull it away (Pullback or move away from it). At first you won’t even be able to focus on the image… However, keep moving the image in and out, relaxing, and it will appear.