Engineering Inside:

2014 Issue 4
Animation

Create an Animation Illusion

December 2014

by Robin Hegg

Every movie, TV show, or YouTube video you’ve ever seen works by creating the illusion of movement using a series of still images. Persistence of vision is the phenomenon that allows this illusion to take place. An afterimage is believed to remain on the retina for approximately one twenty-fifth of a second. When people see two or more similar images, one after the other, at a quick speed, their brain perceives motion, not noticing the blank spaces between images. Even the most advanced movie works using the same principle as the earliest moving image devices. Two of these devices are thaumatropes and flipbooks.

Thaumatropes

"Taumatropio topo e gabbia, 1825" - web. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Taumatropio_topo_e_gabbia,_1825.gif#mediaviewer/File:Taumatropio_topo_e_gabbia,_1825.gif

“Taumatropio topo e gabbia, 1825” – web. Licensed under Public domain via Wikimedia Commons

The word thaumatrope comes from the Greek words “thauma” meaning “magic” or “wonder” and “tropos” meaning “turn.” Thaumatropes are simple devices invented in the 1820s that create an illusion based on persistence of vision. A thaumatrope has two images on either side of a card. When turned or spun quickly, the two images seem to blend into one. This can cause two sets of words or images, one on one side and one on the other, to appear together. A classic thaumatrope is an image of a bird on one side and a birdcage on the other. When the thaumatrope is spun, the bird appears to be inside the cage. Try making your own thaumatrope. Start off with words or a very simple image, then move on to more complicated images.

Materials

Two index cards

Hole punch

2 rubber bands

Pencil

Steps

  1. Holding both cards together, punch a hole at the center of each end of the cards, making sure the holes are horizontal to one another.
  2. Draw a simple picture in the middle of one of the cards.
  3. Place the second card on top of the first card, with the drawing and blank side facing out. Hold the cards up to a light so you can see your original drawing through the cards.
  4. Draw a second drawing on the second card, using the first image as a guide to let you know how the images will fit together.
  5. Turn the second card upside down and place it back to back with the first card.
  6. To attach your cards and make your thaumatrope’s handles, take one rubber band and feed one looped end halfway through one set of holes. Take the other end of the rubber band and feed that loop through the first, pulling it tightly. Repeat on the other set of holes until you have two handles.
  7. Holding on to your handles, turn the rubber bands between your fingers and spin your thaumatrope. How well did your illusion work?

Flip Books Flip books are simple devices but they are also at the heart of every movie you’ve ever seen. Flip books create the illusion of motion between individual pictures and can tell a story. Start with something simple like a ball bouncing across the page or a stick figure walking and jumping. Each drawing will be slightly different from the last, so that when they are viewed quickly one after the other, they will be perceived as one smoothly moving image.

Materials Index cards (about 30, held together with a binder clip) or a Post-It notepad Pencil

Steps

  1. Decide on a simple story you’d like to tell.
  2. On each piece of paper or index card, draw one frame of your story, paying attention to placement so that the change or “movement” between frames is small.
  3. When you’ve finished, flip through your flip book and see how well your illusion worked.

Questions

  1. How well did your illusion work? Did the images line up correctly?
  2. What could you do to make the illusion work better? Feel free to go back and make changes to your images.
  3. What happens when you turn your thaumatrope/flip your flip book slowly? What happens when you do it quickly? Can you catch the speed at which your eyes are tricked?
  4. Do you think it would be possible to create either of these illusions using photographs? What challenges would that present?

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