Persistence of vision display instructables - Persistence of vision: how does animation work? - Explore.



Maybe you’ve seen a persistence-of-vision (POV) illusion before: an array of bright LEDs on the spokes of a spinning bicycle wheel that magically paints colorful animations, light effects, and messages in the night. These visual effects are always good for a “Wow!” — but we’ll go them one better and build a 3-dimensional illusion: the POV Globe.

The term persistence of vision refers to a phenomenon of human vision: a light stimulus lingers as an aftereffect on the retina for about 1/10 of a second. When light stimuli are sequenced in rapid succession, they merge into one continuous image. Scientists still argue how much of this phenomenon is shared between the eye and the brain, but the effect is real — in fact it’s the basis for film and television.

In most POV displays, a linear (1-dimensional) array of LED lights rotates around a single point, like a bike wheel. By measuring their rotation rate and controlling their flashes with millisecond precision, we can create the illusion of a 2-dimensional image lingering in thin air.

In our POV Globe, we’re adding a new dimension. We rotate a curved array of LEDs around a rotational axis, like a planet. When the flashing LEDs draw images in the air — say, the continents of the Earth — the result is a 3-dimensional, spherical illusion: a globe! Of course, our globe can make other images — like the Death Star from Star Wars, a skull, or the Make: logo — appear magically in the room. It all depends on the perfect timing of the LEDs.

This project has 4 main parts: the electronics, which control at least 24–40 LEDs using an Arduino Nano microcontroller and 74HC595 shift registers; the POV Calculator software that breaks down an image into a bit-pattern that your globe can display; the Arduino sketch that breaks this pattern into segments and sends it to the shift registers; and, finally, the mechanics that rotate the LEDs. It’s a moderately difficult project, but with a little experience on the soldering iron and some woodworking and metalworking skills, it can be accomplished in a weekend.

The microcontroller’s job is to issue a predetermined pattern of binary pixels to the large number of LEDs. This data must be sent synchronously with the ring’s rotation, triggered by a magnetic field sensor (a Hall effect probe). But the Arduino has relatively few output pins, so we resort to a trick: We use simple shift register chips, which collect the serially transmitted data (8 bits per chip) and on command make the data parallel (available all at once) at their output pins. This strategy takes advantage of the Arduino’s high-speed serial (SPI) pins, requires much less programming effort, and greatly simplifies the wiring.

Persistence of vision refers to the optical illusion whereby multiple discrete images blend into a single image in the human mind and believed to be the explanation for motion perception in cinema and animated films. Like other illusions of visual perception , it is produced by certain characteristics of the visual system .

Narrowly defined, the theory of persistence of vision is the belief that human perception of motion (brain centered) is the result of persistence of vision (eye centered). That version of the theory was disproved in 1912 by Wertheimer [1] but persists in many citations in many classic and modern film-theory texts. [2] [3] [4] A more plausible theory to explain motion perception (at least on a descriptive level) are two distinct perceptual illusions: phi phenomenon and beta movement .

A visual form of memory known as iconic memory has been described as the cause of this phenomenon. [5] Although psychologists and physiologists have rejected the relevance of this theory to film viewership, film academics and theorists generally have not. Some scientists nowadays consider the entire theory a myth. [6]

The discovery of persistence of vision is attributed to the Roman poet Lucretius , although he only mentions it in connection with images seen in a dream. [7] In the modern era, some stroboscopic experiments performed by Peter Mark Roget in 1824 were also cited as the basis for the theory. [8]

Persistence of vision is still the accepted term for this phenomenon in the realm of cinema history and theory. Early practitioners tried different frame rates, and chose a rate of 16 frames per second (frame/s) as high enough to cause the mind to stop seeing flashing images. Audiences still interpret motion at rates as low as ten frames per second or slower (as in a flipbook ), but the flicker caused by the shutter of a film projector is distracting below the 16-frame threshold. [ citation needed ]

Modern theatrical film runs at 24 frames a second. This is the case for both physical film and digital cinema systems.

Maybe you’ve seen a persistence-of-vision (POV) illusion before: an array of bright LEDs on the spokes of a spinning bicycle wheel that magically paints colorful animations, light effects, and messages in the night. These visual effects are always good for a “Wow!” — but we’ll go them one better and build a 3-dimensional illusion: the POV Globe.

The term persistence of vision refers to a phenomenon of human vision: a light stimulus lingers as an aftereffect on the retina for about 1/10 of a second. When light stimuli are sequenced in rapid succession, they merge into one continuous image. Scientists still argue how much of this phenomenon is shared between the eye and the brain, but the effect is real — in fact it’s the basis for film and television.

In most POV displays, a linear (1-dimensional) array of LED lights rotates around a single point, like a bike wheel. By measuring their rotation rate and controlling their flashes with millisecond precision, we can create the illusion of a 2-dimensional image lingering in thin air.

In our POV Globe, we’re adding a new dimension. We rotate a curved array of LEDs around a rotational axis, like a planet. When the flashing LEDs draw images in the air — say, the continents of the Earth — the result is a 3-dimensional, spherical illusion: a globe! Of course, our globe can make other images — like the Death Star from Star Wars, a skull, or the Make: logo — appear magically in the room. It all depends on the perfect timing of the LEDs.

This project has 4 main parts: the electronics, which control at least 24–40 LEDs using an Arduino Nano microcontroller and 74HC595 shift registers; the POV Calculator software that breaks down an image into a bit-pattern that your globe can display; the Arduino sketch that breaks this pattern into segments and sends it to the shift registers; and, finally, the mechanics that rotate the LEDs. It’s a moderately difficult project, but with a little experience on the soldering iron and some woodworking and metalworking skills, it can be accomplished in a weekend.

The microcontroller’s job is to issue a predetermined pattern of binary pixels to the large number of LEDs. This data must be sent synchronously with the ring’s rotation, triggered by a magnetic field sensor (a Hall effect probe). But the Arduino has relatively few output pins, so we resort to a trick: We use simple shift register chips, which collect the serially transmitted data (8 bits per chip) and on command make the data parallel (available all at once) at their output pins. This strategy takes advantage of the Arduino’s high-speed serial (SPI) pins, requires much less programming effort, and greatly simplifies the wiring.




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