: How are patterns that look like they're moving created? Every time I see a pattern that looks like it's moving, but really isn't, I wonder what the principles are for creating such images.

@Cugini998

The visual system of a human does not have a constant resolution. But rather the resolution is very high in one spot and then decreases as you get further.

Image processing happens immediately when the light hits your retina and is processed in transit to the brain. Altough there are many kinds of processing and clusters of sensors. Mostly they work by detecting change between a central region and a outer one.

These two effects interact so that when the field size increases it reacts differently when the size closely matches the field area. So certain areas around edges become brighter/darker in the periferal vision that closely match the sensor group size.

Since the processing only accumulates change, it means the eye needs to be constantly moving. If it were not moving you would not see anything. Combined with shapes that guide the vision along certain paths of continuty it causes the image to subtly change values on regions which if chosen correctly causes humans to experience movement.

You can try to coregraph the effect. But since the system is so complex its a bit of hit and miss process. Anyway the higher the contrast between the colors the more pronounced the effect is. Hence black and white variants.

Ps: I should add pictures. And bind facts to literature but im waiting for the bus so im not able.

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@Radia289

These images are called illusory motion, and curiously enough, there's still no solid explanation for them (there are strong theories, though).


Some visual scientists think it has to do with fixation jitter:
involuntary eye movements that give the illusion that objects near
what you're fixated on are moving. Others think that when you glance
around the image, motion detectors in your visual cortex get
"confused" by dynamical changes in neurons, and think you're seeing
movements.
(source)


For art, using black and white patterns (I'm guessing color is also ok, though not sure if it fits the definition) to create vivid illusions of motion is based on the concept of Optical Flow:




Optical flow or optic flow is the pattern of apparent motion of
objects, surfaces, and edges in a visual scene caused by the relative
motion between an observer (an eye or a camera) and the scene.


Op art, also known as optical art, is a style of visual art that makes use of optical illusions. Op art works are abstract and usually made in black and white. When the viewer looks at them, the impression given is of movement, hidden images, flashing and vibration, patterns, swelling or warping.

The effects are created through the use of pattern and line. The lines create after- images of certain colors due to how the retina receives and processes light. According to Goethe (Theory of Colours), at the edge where light and dark meet, color arises because lightness and darkness are the two central properties in the creation of color.

Color can also be used for the illusions, and there are three major classes of the interaction of color: simultaneous contrast, successive contrast, and reverse contrast (or assimilation). These are all explained very nicely in the Op art article. This site also has a huge list of illusions and they explain how each one is made or works.

I can't find guides for something like the images you posted, but it might be similar to the Rotating Snake, where totation direction depends on the polarity of the luminance steps.

Now, on how to make them. Apparently each illusion requires quite a lot of work. However, because there are some principles you can follow, there existing guides on how to create stuff like this:

How to Create a Moving Image Optical Illusion by PSDTuts

I think their explanation sums it up quite nicely: When we look at the image below, our brain tries to convert it from 2D to 3D. This is because the borders around the ellipses are inconsistent. This confuses us and creates an illusion of movement.

The final result for that guide will be an image similar to this:



While your images use a lot of color, I think the principles behind them are related to Op art. Well, at least they both use lines and patterns!

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