ORIGAMI · T-REX · EYES · FOLLOW · 3D · ILLUSION · DESKTOP TOY
I SEE YOU !
FIND OUT HOW THIS CREEPY EFFECT WORKS
start
HIS EYES FOLLOW YOU ...
The T-rex paper model was designed by magician Jerry Andrus, in honour of popular writer Martin Gardner. Have you heard of them? Gardner was famous for the Mathematical Games and puzzles he wrote about, in the Scientific American magazine, for 25 years... He was also deeply interested in magic, science and literature.
But how does it work?!
WHAT's YOUR GUESS?
It is a digital screen that is playing a T-Rex video.
It has a motion sensor that detects our movement.
There are tiny gears and a motor in its neck.
None of the above
WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! ·
IT HAS TO DO WITH OUR BRAIN
CLICK ON EACH BUBBLE TO FIND OUT HOW THE ILLUSION GETS CREATED IN OUR BRAIN
Our brain WANTS to see faces
Our brain makes 3D from 2D
There's Motion parallax when you move
Even concave looks convex
OUR BRAIN MAKES 3D FROM 2D
We say that an object is 2D if it has only two dimensions - length and width. And 3D if it also has depth/height.
The lines that make up this cube are all drawn on the screen's flat surface. So you KNOW that the figure exists only in 2D. Yet, you SEE it as a 3D cube! Not just that, you can see two different cubes, depending on where you think the red dot is - at the bottom left of the front face, OR the bottom left of the back face. But you can see only one of them at a time :) This is called a Necker cube, named after its creater, Louis Albert Necker (1786 - 1861), who was a Swiss crystallographer.
BUT Why?
BECAUSE...
SEE FOR YOURSELF
Hold out your right arm or left arm in front of you. Hold your thumb up. Look at any object which is a few feet away and is partly hidden by your thumb. Now look at the same object, first with your left eye closed. Being in the same position, look with your left eye open and right eye closed. What happens? Does the object seem to shift right and left? This is because our two eyes see the world from slightly different positions (~6-7cm apart). So the image in each retina looks slightly different. The brain uses clues from these differences to estimate distance and depth.
Our eyes see only in 2D. That is, when you look at an object, the image projected on our retinas are flat. Looking at that image alone, you cannot tell if the object is near or far. Or if its surface is sticking out or has holes. So the brain has come up with clever ways to convert the flat image into a 3D map. Without this, it would be very difficult for us to do even basic functions like picking up a cup, or walking around!
WHAT CLUES DOES THE BRAIN USE?
1. Occlusion
But if they overlap, then parts of one object seem to be 'occluded' (meaning - hidden) behind the other. So the brain imagines depth.
Two objects that are side-by-side don't seem to have any depth.
WHAT CLUES DOES THE BRAIN USE?
2. Relative size
Objects appear smaller when they are far away (Like how aeroplanes look so tiny when you see them in the sky). So the brain uses size to estimate distance.
In this pic, it looks as though a giant is running behind a dwarf. But look closer... Why do you think this happens?
WHAT CLUES DOES THE BRAIN USE?
3. Shadows
Why does this happen?
In the natural world, most of the light comes from above us (sun and moon). We evolved in such a world for a long long time. So our brains associate certain patterns in the shadow with specific profiles - If the object is raised, it is bright on top and has shadows beneath. In case of holes, the top is dark and the bottom is brighter.
Which set of these dots are bumps and which ones are dented?
Now turn your screen upside down to look at the same picture. Which set has bumps and which has dents?
WHAT CLUES DOES THE BRAIN USE?
3. Shadows
These are images taken from space of the same spot on Ceres (the largest object in the asteroid belt between Mars and Jupiter). Is it actually a dome or a crater? Make a guess!
Back to menu
MOTION PARALLAX
Have you looked out the window when travelling in a car or a train? Imagine you were viewing this scene. Which of these - the deer, the tree or the mountain - would move past the fastest? Which would go by, the slowest?
MOTION PARALLAX
You would observe that objects that are closest to the vehicle (like the deer in the pic) appear to move past very fast. Whereas objects in the distance (like the mountain in the background) would appear to almost stay still. Our brain uses this difference to figure out how far the objects are from us. Animators and video game creators make use of this idea to 'create' a sense of motion in their scenes. They do this by splitting a scene into multiple layers and giving them different speeds. Astronomers use the same concept to calculate the distance of stars!
Back to menu
OUR BRAIN 'WANTS' TO SEE FACES
WE EVEN SENSE EMOTIONS IN THESE 'FACES'!
WHY DO WE SEE FACES EVERYWHERE?
When we evolved into humans, recognising faces became a useful evolutionary trait to help us identify family members and to read their emotions. We also got tuned to it because it was necessary to differentiate between friends and enemies. It was so important for survival that we have a dedicated area in our brains for detecting faces. It is called Fusiform Face Area. To recognise something as a face, our brain does not even need detailed features. If anything resembles two eyes, we automatically pull in other details to stand in for a mouth or nose. So we end up seeing faces even in everyday objects - this is called pareidolia. Though these faces aren't real, this mistake is harmless.. but not identifying a real face might be dangerous. So the brain chooses to err on the side of caution.
Back to menu
EVEN CONCAVE LOOKS CONVEX
Have you seen this hollow mask illusion?
Though the mask is hollow on one side, we see both sides as proper faces!
HOW DOES IT HAPPEN??
With the mask facing you, let's say you move slightly towards your left. Then one half of the mask face will form a larger angle than the other half. This configuration is the same as when the mask is facing away from you, but you had moved towards your right instead. So while making sense, the brain is free to choose from either of these options. Since the brain is tuned to seeing faces, it chooses the convex version (since that's how faces are)! This is also why you 'see' the mask flip its direction of rotation.
Mask away from you (concave)
Mask towards you (convex)
a > b
a > b
PLUS, SHADOWS ENHANCE THE EFFECT
This is very similar to the crater-dome illusion that we saw earlier. This is also why museums have such careful lighting around their exhibits - you may not even see the effect otherwise!
MATCH THE CUES IN T-REX
There's Motion parallax when you move
Even concave looks convex
Our brain WANTS to see faces
Our brain makes 3D from 2D
Drag and drop these speech bubbles into the right cues above:
There are shadows below his eyebrows and eyes. But the top of his eyebrows and snout are shiny and bright. His face is larger than his forearms, neck and head
His face is actually caved in, and not raised outward.
When you move, his snout seems to move faster than the back of his head
His eyes look lively and realistic.
HERE'S HOW TO MAKE HIM
Use a scale to make the folds crisp and neat. After assembling him, use 2-3 layers of tape to secure the joints well.
IT HAS TO DO WITH OUR BRAIN
CLICK ON EACH BUBBLE TO FIND OUT HOW THE ILLUSION GETS CREATED IN OUR BRAIN
IT HAS TO DO WITH OUR BRAIN
Have you seen this hollow mask illusion?
Two objects that are side-by-side don't seem to have any depth.
IT HAS TO DO WITH OUR BRAIN
Have you seen this hollow mask illusion?
Two objects that are side-by-side don't seem to have any depth.
PLUS, SHADOWS ENHANCE THE EFFECT
We would love to display your light canvas in the TinkerTime virtual gallery... Take a photo or short video of your Light Canvas while rotating the filters. Capture the colours shifting — that movement is part of the artwork!
Text button
SHARE YOUR FEEDBACK...
MORE FUN STUFF YOU CAN MAKE...
FLOATING CUBE ILLUSION
AMES ROOM ILLUSION
Exit
Stereoscopes
Did you know that this idea can also be used to trick our brain into seeing in 3D? That's exactly what happens in 3D movies. Before movies, there were stereoscopes that enabled people to see photographs in 3D.
Click to view the fascinating history of Stereoscopes
HEAD-TURNERS
Mathu Shalini
Created on March 6, 2026
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Transcript
ORIGAMI · T-REX · EYES · FOLLOW · 3D · ILLUSION · DESKTOP TOY
I SEE YOU !
FIND OUT HOW THIS CREEPY EFFECT WORKS
start
HIS EYES FOLLOW YOU ...
The T-rex paper model was designed by magician Jerry Andrus, in honour of popular writer Martin Gardner. Have you heard of them? Gardner was famous for the Mathematical Games and puzzles he wrote about, in the Scientific American magazine, for 25 years... He was also deeply interested in magic, science and literature.
But how does it work?!
WHAT's YOUR GUESS?
It is a digital screen that is playing a T-Rex video.
It has a motion sensor that detects our movement.
There are tiny gears and a motor in its neck.
None of the above
WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! · WELL DONE! ·
IT HAS TO DO WITH OUR BRAIN
CLICK ON EACH BUBBLE TO FIND OUT HOW THE ILLUSION GETS CREATED IN OUR BRAIN
Our brain WANTS to see faces
Our brain makes 3D from 2D
There's Motion parallax when you move
Even concave looks convex
OUR BRAIN MAKES 3D FROM 2D
We say that an object is 2D if it has only two dimensions - length and width. And 3D if it also has depth/height.
The lines that make up this cube are all drawn on the screen's flat surface. So you KNOW that the figure exists only in 2D. Yet, you SEE it as a 3D cube! Not just that, you can see two different cubes, depending on where you think the red dot is - at the bottom left of the front face, OR the bottom left of the back face. But you can see only one of them at a time :) This is called a Necker cube, named after its creater, Louis Albert Necker (1786 - 1861), who was a Swiss crystallographer.
BUT Why?
BECAUSE...
SEE FOR YOURSELF
Hold out your right arm or left arm in front of you. Hold your thumb up. Look at any object which is a few feet away and is partly hidden by your thumb. Now look at the same object, first with your left eye closed. Being in the same position, look with your left eye open and right eye closed. What happens? Does the object seem to shift right and left? This is because our two eyes see the world from slightly different positions (~6-7cm apart). So the image in each retina looks slightly different. The brain uses clues from these differences to estimate distance and depth.
Our eyes see only in 2D. That is, when you look at an object, the image projected on our retinas are flat. Looking at that image alone, you cannot tell if the object is near or far. Or if its surface is sticking out or has holes. So the brain has come up with clever ways to convert the flat image into a 3D map. Without this, it would be very difficult for us to do even basic functions like picking up a cup, or walking around!
WHAT CLUES DOES THE BRAIN USE?
1. Occlusion
But if they overlap, then parts of one object seem to be 'occluded' (meaning - hidden) behind the other. So the brain imagines depth.
Two objects that are side-by-side don't seem to have any depth.
WHAT CLUES DOES THE BRAIN USE?
2. Relative size
Objects appear smaller when they are far away (Like how aeroplanes look so tiny when you see them in the sky). So the brain uses size to estimate distance.
In this pic, it looks as though a giant is running behind a dwarf. But look closer... Why do you think this happens?
WHAT CLUES DOES THE BRAIN USE?
3. Shadows
Why does this happen?
In the natural world, most of the light comes from above us (sun and moon). We evolved in such a world for a long long time. So our brains associate certain patterns in the shadow with specific profiles - If the object is raised, it is bright on top and has shadows beneath. In case of holes, the top is dark and the bottom is brighter.
Which set of these dots are bumps and which ones are dented?
Now turn your screen upside down to look at the same picture. Which set has bumps and which has dents?
WHAT CLUES DOES THE BRAIN USE?
3. Shadows
These are images taken from space of the same spot on Ceres (the largest object in the asteroid belt between Mars and Jupiter). Is it actually a dome or a crater? Make a guess!
Back to menu
MOTION PARALLAX
Have you looked out the window when travelling in a car or a train? Imagine you were viewing this scene. Which of these - the deer, the tree or the mountain - would move past the fastest? Which would go by, the slowest?
MOTION PARALLAX
You would observe that objects that are closest to the vehicle (like the deer in the pic) appear to move past very fast. Whereas objects in the distance (like the mountain in the background) would appear to almost stay still. Our brain uses this difference to figure out how far the objects are from us. Animators and video game creators make use of this idea to 'create' a sense of motion in their scenes. They do this by splitting a scene into multiple layers and giving them different speeds. Astronomers use the same concept to calculate the distance of stars!
Back to menu
OUR BRAIN 'WANTS' TO SEE FACES
WE EVEN SENSE EMOTIONS IN THESE 'FACES'!
WHY DO WE SEE FACES EVERYWHERE?
When we evolved into humans, recognising faces became a useful evolutionary trait to help us identify family members and to read their emotions. We also got tuned to it because it was necessary to differentiate between friends and enemies. It was so important for survival that we have a dedicated area in our brains for detecting faces. It is called Fusiform Face Area. To recognise something as a face, our brain does not even need detailed features. If anything resembles two eyes, we automatically pull in other details to stand in for a mouth or nose. So we end up seeing faces even in everyday objects - this is called pareidolia. Though these faces aren't real, this mistake is harmless.. but not identifying a real face might be dangerous. So the brain chooses to err on the side of caution.
Back to menu
EVEN CONCAVE LOOKS CONVEX
Have you seen this hollow mask illusion?
Though the mask is hollow on one side, we see both sides as proper faces!
HOW DOES IT HAPPEN??
With the mask facing you, let's say you move slightly towards your left. Then one half of the mask face will form a larger angle than the other half. This configuration is the same as when the mask is facing away from you, but you had moved towards your right instead. So while making sense, the brain is free to choose from either of these options. Since the brain is tuned to seeing faces, it chooses the convex version (since that's how faces are)! This is also why you 'see' the mask flip its direction of rotation.
Mask away from you (concave)
Mask towards you (convex)
a > b
a > b
PLUS, SHADOWS ENHANCE THE EFFECT
This is very similar to the crater-dome illusion that we saw earlier. This is also why museums have such careful lighting around their exhibits - you may not even see the effect otherwise!
MATCH THE CUES IN T-REX
There's Motion parallax when you move
Even concave looks convex
Our brain WANTS to see faces
Our brain makes 3D from 2D
Drag and drop these speech bubbles into the right cues above:
There are shadows below his eyebrows and eyes. But the top of his eyebrows and snout are shiny and bright. His face is larger than his forearms, neck and head
His face is actually caved in, and not raised outward.
When you move, his snout seems to move faster than the back of his head
His eyes look lively and realistic.
HERE'S HOW TO MAKE HIM
Use a scale to make the folds crisp and neat. After assembling him, use 2-3 layers of tape to secure the joints well.
IT HAS TO DO WITH OUR BRAIN
CLICK ON EACH BUBBLE TO FIND OUT HOW THE ILLUSION GETS CREATED IN OUR BRAIN
IT HAS TO DO WITH OUR BRAIN
Have you seen this hollow mask illusion?
Two objects that are side-by-side don't seem to have any depth.
IT HAS TO DO WITH OUR BRAIN
Have you seen this hollow mask illusion?
Two objects that are side-by-side don't seem to have any depth.
PLUS, SHADOWS ENHANCE THE EFFECT
We would love to display your light canvas in the TinkerTime virtual gallery... Take a photo or short video of your Light Canvas while rotating the filters. Capture the colours shifting — that movement is part of the artwork!
Text button
SHARE YOUR FEEDBACK...
MORE FUN STUFF YOU CAN MAKE...
FLOATING CUBE ILLUSION
AMES ROOM ILLUSION
Exit
Stereoscopes
Did you know that this idea can also be used to trick our brain into seeing in 3D? That's exactly what happens in 3D movies. Before movies, there were stereoscopes that enabled people to see photographs in 3D.
Click to view the fascinating history of Stereoscopes