What isthe animated optical illusions

Have you heard of animated optical illusions?

Animated optical illusions is a technique that creates the illusion of movement in still images. It uses a specially designed overlay with vertical stripes that, when moved across the underlying image, reveals different parts of the image sequentially, giving the impression of animation.

This toy is known by various names. Even if you haven't heard the term "animated optical illusions" you might be familiar with names like slit animation, striped animation, scanimation, picket fence animation, and grid barrier animation.

The Mechanism of Animated Optical Illusions

So, why do animated optical illusions appear to move? It's amazing that a still image can look like people or animals when overlaid with a striped moving sheet ( a transparency film with striped patterns ), and even more intriguing that they appear to move when you slide the striped moving sheet. This phenomenon involves the mysterious workings of the human brain. On this page, we will show you the mechanism behind the apparent motion in animated optical illusions.

On the "How to Make" page, using two or three illustrations, we will demonstrate step by step how to make animated optical illusions. Please check.

Once you understand the mechanism, you can easily make animated optical illusions using image editing software like Photoshop or Illustrator. If this page piques your interest in animated optical illusions, please give it a try.

The Mysterious Brain Function That Makes Still Illustrations Appear to Move

Why do animated optical illusions appear to move? The brain functions needed to make animated optical illusions appear to move can be broadly divided into two:

The brain recognizes similar objects seen consecutively as the same object and fills in the gaps between them.

When part of an object is hidden from view, the brain uses experience and knowledge to fill in the hidden parts and instantly recognize the whole object.

This might be a bit hard to understand in words, but it becomes clear with examples.

Let's first look at the brain function where "the brain recognizes similar objects seen consecutively as the same object and fills in the gaps between them."

Think of a flipbook. When you flip through the pages, the illustrations that change slightly on each page appear to move. The smaller changes, the smoother the motion appears, but even with larger changes, there is a sense of movement. Why do still illustrations appear to move? This involves the same brain function as animated optical illusions.

When you flip through the pages of a flipbook, you see the illustrations one after another. The brain recognizes them as the same object and tries to fill in the gaps between the changes. This process results in the brain creating intermediate illustrations, making the still illustrations appear to move.

Have you ever felt that the flashing red lights at a railroad crossing, blinking alternately, seem to move sideways? This happens because the brain creates the moving light between the continuously flashing red lights.

Let's experience this brain function using two illustrations. Click on the illustrations below to switch between them alternately.

How about this? Can you see the ball that isn't supposed to be drawn between the illustrations? This is the first brain function needed to make animated optical illusions appear to move.

The Mysterious Brain Function That Makes Hidden Illustrations Visible

Now, let's take a look at the second brain function: "When part of an object is hidden from view, the brain uses experience and knowledge to fill in the hidden parts and instantly recognize the whole object."

For example, when you look at a close-up photo of a giraffe's neck, you can imagine the entire giraffe from its shape, color, and pattern. You might even be able to judge whetherit's a real giraffe or a stuffed one based on the texture.

How is this possible?It's because you are familiar with giraffes, having seen real giraffes or giraffe toys in books, on TV, or at the zoo. You might think this is obvious;it's an amazing ability of humans to see things that aren't there.

Look at the illustration below.

We've hidden part of the previous illustration with black stripes. This illustration is half-hidden by black stripes, but how can we still recognize that it's a picture of a person and a ball?

While much about how the brain works is still a mystery, experiments and research suggest three key factors needed for recognizing hidden parts:

The hidden part (striped moving sheet) has a regular pattern.

The hidden part (striped moving sheet) covers less than 80% of the entire illustration.

The visible part (illustration) has continuity.

The Three Factors for Recognizing Illustrations Hidden by a Striped Moving Sheet

To understand the first factor, let's revisit the illustration shown earlier. The striped pattern hiding the illustrations is made up of straight lines arranged at regular intervals. There's a regular pattern to it, right?

Let's try hiding it with a pattern that has no regularity. Just like the illustration above, half of the illustration is hidden. How is it? Compared to the illustration above, isn't it harder to recognize the person and the ball? When there is no regularity like this, it becomes difficult to recognize that it is the same thing, even if you know the original illustration.

Next, let's look at the second factor: "The hidden part covers less than 80% of the entire illustration." This is crucial for the number of frames in animated optical illusions.

In the example below, we gradually increased the width of the black stripes to see how the hidden part affects the visibility of the illustration.

You can see that as the width of the black stripes becomes thicker, it gradually becomes more difficult to recognize the person and the ball.

We'll go into more detail on the "How to Make" page, but the number of frames in an animated optical illusion corresponds to the width of the black stripes.

To increase the number of frames, the width of the black stripes needs to be thickened. Depending on the illustration used for the animated optical illusions, it might not be possible to increase the number of frames. Therefore, it is very important to determine the appropriate thickness of the black stripes for each illustration.

Generally, five or six frames are considered the maximum for the animated optical illusions.

In the previous example, we gradually increased the width of the black stripes to see how the hidden part affects the visibility of the illustration. This corresponds to a striped moving sheet with three to five frames.

Finally, let's focus on the factor, "The visible part has continuity."

Look at the example below and try to imagine what is hidden by the striped moving sheet. You can imagine a triangular shape. Why is that? Even though there might be nothing under the striped moving sheet, when you place a ruler along each side of the triangle, you can see that the visible parts are aligned in a straight line.

This means the parts you can see are connected in a straight line. When you assume the hidden parts continue this line, your brain perceives the straight line under the striped moving sheet. This perception leads your brain to recognize a triangle formed by the three connected sides. Your brain does not interpret the hidden parts as empty.

This principle applies to curved lines and colors as well. If the colors before and after the stripes are the same, your brain assumes the same color is under the stripes.

Therefore, illustrations for animated optical illusions must be simple and easy to understand. Illustrations with complex lines or gradually changing colors lose continuity when hidden by a striped moving sheet, making them unsuitable for animated optical illusions.

Isn't the human brain fascinating? It perceives still objects as moving and sees what isn't there. Animated optical illusions are a toy that takes advantage of such amazing brain functions.