Create stereogram3/18/2023 What Works and Does Not Work in a Stereogram A question we hear often is can you make a stereogram from a black and white photo? The answer is no. The pattern in the stereogram shown above right repeats 6 times. Patterns that are random and textured, such as the flowers, minimize the obvious pattern shifts, A well designed pattern also creates more depth and detail. The Hidden Image Stereogram (above right) contains a 3D sphere. When we view the stereogram our brain detects these changes and combines the subtle shifts to create the illusion of a 3D object. Our stereogram software repeats the pattern like wallpaper and makes subtle shifts to the pattern in each panel. The second component in a Hidden Image Stereogram is a repeating pattern such as the colorful flower pattern shown on the left. This is how sphere is interpreted by the Stereogram software. The diagram above shows how the roundness of the sphere is sliced into 256 thin layers. It is lighter in the center and becomes darker as it moves out to the edges. A sphere rendered as a depth map image (shown above left) is very different. Without these "visual cues" it would just be a flat red circle. ![]() In real life, we identify a sphere, such as the example shown on the left in red, because it has a core shadow and a highlight. It’s like slicing an objects into 256 thin layers. All the other shades of gray represent the layers of depth in between. White comes to the very front and black goes all the way to the back. A depth map image is a black and white image comprised of 256 shades of gray that our software uses to create three dimensional depth. The specialized stereogram software we use reads the light and dark information from the depth map image and uses this information to create a magical 3D image. Hidden Image Stereograms (HIS), made from seemingly random patterns are crafted from two components: the repeating pattern and the depth image. And the best part is after you have seen your first 3D Stereogram, it gets easier and easier to see the next and the next and the next. ![]() Your brain combines these two slightly different views into what we perceive as 3D depth. Whatever you are looking at will appear to jump back and forth. How It Works Each of our eyes sees the same scene but from a slightly different point, You can see this difference by looking out a window and alternately closing one eye and then the other eye and repeating this a few times. But the good news is that the great majority of us were born with fully functioning stereographic vision and are perfectly able to enjoy the magic of 3D Stereograms. And some people have vision problems that make it difficult or impossible to see stereo-graphically. There are rare exceptions in which some people are physically unable to process stereographic information. All you need are two eyes, a Stereogram or two with which to practice, and a bit of patience. If you have never been able to see a 3D Stereogram, you're in for a magical experience.
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