# Never-ending Penguin Stair

This is a variation on M.C.Escher’s 1960 lithograph Ascending and Descending.  At first we see the staircase leading into the distance, and ending in mid-air, but then at about 15 seconds in, the furthest point of the staircase  lines up with the nearest point.  At the same time the perspective cues that made the distant platform a bit smaller, and a bit paler, than the nearest platform vanish so that they appear the same size.  Our brains then assume that they connect up, even though the result is a stair that could not exist in real 3D space. From 20 seconds in, the penguins entering from the right are always heading towards us in an endless loop, but never get any nearer.

This post is an update on a much earlier one, from 2008.

# A Funny Turn

It may take a bit of practice, but you’ll be able to see the silhouette dinosaur rotating either way around.  One way round, it’s  rotating just like the top right hand of the four coloured dinos.  To see it rotate the other way round, start with the head facing left.  Then try imagining that the head is getting nearer to you as it goes lower.  Once you’ve seen the rotation go both ways, it tends to change spontaneously from one to the other.

I’m not great at imagining 3D shapes moving in space. When I set this up, I assumed that when the silhouette rotates the way around that doesn’t match the top right hand coloured dinosaur, it  will instead match one of the two left hand dinos, but half a rotation out of step.  The top left one is just a mirror reflection of the top right coloured one, and the lower left one a time-reversed version of it.  But I wasn’t sure which of the those left hand dinos it would match.  (The lower right coloured dino is a reflection plus a time-reversal of the top right one.  That switches the rotation twice – back to matching the way around the top right dino goes).

But the silhouette dino, when seen as rotating opposed to the top right dino, isn’t like either of the left hand versions!  In those, the head is always nearest to us when it’s at its highest, and furthest from us when it is lower down.  With the silhouette view clockwise, it’s the other way round:  the head is nearest to us when its low down.  I think it’s an impossible view, invented by the brain.  There’s no way I can get the real dino to give me that view.  (Actually – full disclosure – I didn’t film a real dinosaur.  It’s a model).

I haven’t quite puzzled out why the views work like this.

Extra:  18/2/20

I found the explanation in a chapter in the wonderful Oxford Compendium of Visual Illusions,  Nicolaus F. Troye “The Kayahara silhouette illusion” pp 582-585.

The key is that the sihouette version image is not just rotationally ambiguous (it rotates clockwise or anti-clockwise), even as a static image it’s also depth ambiguous.  So the silhouette above can either appear just like the upper left dino in the picture, head nearest to us, or a bit like the lower centre dino, head furthest away.  Both ambiguities – rotation and depth – can only flip at the same time.

But note that the silhouette and the picture of the dino with head more distant are not quite the same.  That’s because the dino extends so far into depth that it shows perspective effects.  First, with reversal our viewpoint slightly changs.  But more strikingly, when we see the silhouette dino with its head furthest from us, the head looks far too large.  That’s because of the size constancy effect – we tend perceptually to enlarge the size of more distant objects.  So here, when the head is seen as more distant, it also appears far too large, and the tail, conversely, too small.

That also applies with the moving version, when the silhouette dino is seen as revolving anti-clockwise:  its head seems to shrink as it rotates towards us, and to expand as it rotates away.

# Waiting for Shining Person (a new optical illusion cartoon)

Here is a new animation in our series of animated illusion cartoons, Waiting for Shining Person.  (As with our earlier cartoons, It may run jerkily on first run-through.  It should be fine thereafter.)

Compression for Flash has slightly reduced the effect. If possible, view Waiting for Shining Person as a
Quicktime Movie

These cartoons are meant to work just like a three- or four-frame cartoon in a newspaper – each one presents a situation that ends with a punch-line.  The cast of characters are all illusion figures of different kinds, but each cartoon depends on a particular illusion effect.

So the cartoons are a new art form – but I’m not sure they’re entirely successful.

The main illusion to watch out for in the movie is the glare effect, which radiates from the face of the mysterious Shining Person:

# Animated Illusion Cartoons – re-posting of Chicken and Leaf

Woops, slight technical glitch with the original post of this, just before Christmas. So this is a re-posting of the third of our animated illusion cartoons, Chicken and Leaf. It may still run jerkily on first run through, should be OK second time around.

These cartoons are meant to work just like movie versions of a three- or four-frame cartoon in a newspaper – each one presents a situation that ends with a punch-line.  The cast of characters are all illusion figures of different kinds, but each cartoon depends on a particular illusion effect.

The main illusion effects to watch out for in this movie are tessellations, and especially the final transformation, which transforms across the image at the same time as it transforms locally:

You can also view Chicken and Leaf as a
Quicktime Movie

You can also see our this cartoon along with the previous ones in our Animated Illusion Cartoon category.

I’m fascinated by the effect that the movie ends with – a tessellation that transforms in space and in time. Tessellation (or tiling) wizard M.C.Escher was brilliant at these transforming patterns, as in his Metamorphosis prints, but of course couldn’t do animations.  I’m sure he’d have done the animations if he could, but without a computer they’d have taken years. In my animation there are two sequences of transformations, first where the pattern morphs in sync all over the screen – a number of people have done those – and then the one that morphs across the image as well as in time.  I’m not aware anyone else has done one of those.  Please let me know if so, I’d love to see it – and otherwise, I hope if you’re an animator you’ll be provoked into doing a better one than mine.

# Animated illusion cartoon – post no. 2

Here’s a new chance to see illusions as you’ve never seen them before (unless of course you viewed our first post on animated illusion cartoons).

This one is STAG and the SNOW FAIRY.  The illusion it features, on which we have an earlier post, also with an animation, is revolving heads.

You can also view Stag and the Snow Fairy as a
Quicktime Movie

You should also be able to download Stag and the Snow Fairy for mobiles. This is a bit experimental, so please let us know if it works:

formatted (filesize 924 KB, .mp4 format) for
mobiles EXCEPT Iphones

formatted (filesize 3.2 MB, m4v format), for
IPHONES

# Illusion animated cartoons

The world of illusion as you’ve never seen it before:

Here’s the first of a series of half minute or so optical illusion animated cartoons… also available as a Quicktime Movie.

This cartoon features a new version of the well-known rotating heads illusion.

And here’s the second …. also available as a Quicktime Movie.

This cartoon features two kinds of ambiguous images. One is the famous Duck/rabbit illusion and the other a new ambiguous image, first seen on this site, the mask/skull illusion.

More cartoons to follow over the next few weeks, along with illusion posts as last year.