Casually, I was visiting this site about optical illusions:

http://www.ritsumei.ac.jp/~akitaoka/index-e.html

just before reading the post from Sebastian with the unexpected optical
illusion, so I didn't resist the temptation to quickly try out with POV
some variations from one of Akiyoshi's illusions.

Warning: this effect can make you feel sick!

--
Jaime

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That is rather weird. Why does it look like things are moving?!?

Jaime Vives Piqueres <jai### [at] ignoranciaorg> wrote:
> Casually, I was visiting this site about optical illusions:
>
> http://www.ritsumei.ac.jp/~akitaoka/index-e.html
>
> just before reading the post from Sebastian with the unexpected optical
> illusion, so I didn't resist the temptation to quickly try out with POV
> some variations from one of Akiyoshi's illusions.
>
> Warning: this effect can make you feel sick!
>
> --
> Jaime

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Ha! That's just crazy!

I think Im gonna have to lie down for a second...

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"Jaime Vives Piqueres" <jai### [at] ignoranciaorg> wrote in message 
news:44dc7989@news.povray.org...

> Warning: this effect can make you feel sick!

     Almost!  ;)  Nice one Jaime.

      ~Steve~


>
> --
> Jaime
>
>

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"jhu" <nomail@nomail> wrote:
> That is rather weird. Why does it look like things are moving?!?

Short answer:  Your brain is messing with you.

Longer answer:  Your brain is the world's most sophisticated image
processor.  It continually "Photoshops" everything you look at before it
allows "you" (i.e., your consciousness) to see it.

This subconscious preprocessing identifies and analizes patterns in what you
look at, so that when "you" have to act or make decisions about what you
see, "you" don't have to figure out what it is that you're looking at.  An
example is when you see a familiar face.  You didn't have to think about
it; you recognize the person instantly--or so it seems.  But *something*
inside your head had to figure out that it was a face, and then figure out
whose face.

It's actually a survival adaptation.  People who saw a lion, but had to
consciously figure out what they were seeing, got eaten.  People who could
not recognize an enemy on sight ended up in very undesirable situations.

However, as is common with automated processes, things can go wrong; and as
is the case with man-made computers, your subconscious brain is none the
wiser.  This is how people like Richard Hoagland can write entire books
claiming that an unremarkable hill on Mars is actually a face built by
aliens.  The phenomenon is called pareidolia, and it's also behind all
these images of Jesus and Mary in odd places like an underpass water stain,
a burrito, the M16 nebula, and the lastest, an oil stain in a baking pan.

Biology tolerates these errors; natural selection favors the false
positives.  As the lucid schizophrenic says, "Just because i'm paranoid
doesn't mean they're not out to get me."  Nobody ever died by wasting their
money on Mr. Hoagland's books, but brains that report false negatives get
eaten.

Nevertheless, these errors can be fun, and even useful.  Many people can see
a face in the Moon.  As children, we all used to see animals and other
shapes in  the clouds.  Nobody needs to be an artist to communicate a face;
a circle, and arc, and two dots will do. :)  Looks like you can even skip
the circle! :)  Bold, black-and-white stylized drawings of people
communicate "Men's Room," "Ladies' Room," and "pedestrian crossing" better
than photographs would.

For Akiyoshi's illusions, i think the key is that the brain expects a
real-life scene in 3-D space.  The preprocessor doesn't know what to make
of artificial 2-D images that don't represent reality.

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Nicely explained, Cousin. :)  Hmm... Some 20 minutes later, I still feel 
a little giddy, but then again, I was never one for the fun fair!

      ~Steve~

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Cousin Ricky wrote:
> Short answer:  Your brain is messing with you.

There's a lovely book published many years ago by Byte magazine called 
"The Brains of Men and Machines."  It describes everything from vision, 
kinesthetics, planning, emotion, and actuation in terms of computers, an 
in particular op-amps and algorithms. For example, your eyes have 
already separated what you see into edges and objects before the signal 
leaves your eyeballs, and has separated objects from each other and 
background and split out the positional information from the visual 
information before it gets all the way to your brain. There are "blind" 
people who know something is there but doesn't know what it is, because 
the "what is it" part got broken while the "where is it part" was 
undamaged, for example. The book is both readable and fascinating.

I think I'll put it on my stack to read again. The nice thing is, stuff 
like this really doesn't go out of date. Brains don't evolve as fast as 
computers.

Ernest Kent
ISBN 0-70-034123-0



-- 
   Darren New / San Diego, CA, USA (PST)
     This octopus isn't tasty. Too many
     tentacles, not enough chops.

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>
> I think I'll put it on my stack to read again. The nice thing is, stuff
> like this really doesn't go out of date. Brains don't evolve as fast as
> computers.
>

<rant type="OT" degree="mild">
That would be true if we knew everything about the brain to begin with.
Alas, to a great extent, we must make junk up (an exaggeration - careful
reasearch leads to very resonable hypothoses and occasionally
full-and-proper theories of brain function) but the field is still very
much in flux - in fact, if I am recalling this correctly, more than any
other filed, biomedical or otherwise, in science today . We just don't know
that much now - let alone 5 years ago. Look up whether memory is holographic
or localed (located?) in a book that is still in print, one from five years
ago, and then ask a couple people who know. Even with only two options, I
bet you get 5 differnt answers ;) At least look to see if your library has
something newer before you return to an old favorite- too much cool stuff
has happened to miss.
</rant>

-s
5TF!

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stm31415 wrote:
> That would be true if we knew everything about the brain to begin with.

I knew when I posted that that someone would bring that up. The 
difference, however, is that anything simple enough to talk about in a 
layman's text isn't likely to be wrong in details simplified enough to 
be so presented. That is, the author isn't writing about anything 
complex enough that it's liklely to be the cutting-edge of knowlege.

-- 
   Darren New / San Diego, CA, USA (PST)
     This octopus isn't tasty. Too many
     tentacles, not enough chops.

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jhu wrote:
> That is rather weird. Why does it look like things are moving?!?

I don't really know the "why", but I deduced the "what" from Akiyoshi's
illusions, so I was able to reproduce the effect with POV-Ray. It has to
do with the use of complementary colors separated by black and white
zones. When disposed on certain repeating but changing structures, these
will cause the impression of motion in the direction of the
transformation. Here is a little example:

/*

     Color motion experiments after Akiyoshi's illusions:

     http://www.ritsumei.ac.jp/~akitaoka/index-e.html

     To obtain a different pattern, change the r_op seed

     Jaime Vives Piqueres 2006

*/
global_settings{max_trace_level 8}
#include "colors.inc"
#include "textures.inc"
#include "functions.inc"

// complementary colors
//#declare c1=rgb <.75,0,.25>;
//#declare c2=rgb <.25,.75,0>;
#declare c1=rgb <1,.5,0>;
#declare c2=rgb <0,.5,1>;

// repeating pattern
#declare r_op=seed(630);
#declare xd=1000*rand(r_op);
#declare yd=1000*rand(r_op);
#declare f_pig=function{
    pattern{
     gradient x
     rotate 360*rand(r_op)*z
     warp{repeat x flip x}
    }
}
#declare p1=
pigment{
     function{
      f_pig(x+xd,y+yd,0)
     }
     color_map{
      [0.0 rgb 1]
      [0.1 rgb 1]
      [0.1 c1]
      [0.5 c1]
      [0.5 rgb 0]
      [0.6 rgb 0]
      [0.6 c2]
      [1.0 c2]
     }
}
plane{z,2
    texture{
     pigment{p1}
     finish{Luminous}
     scale .125
    }
}

// kaleidoscope for the repeating
#declare kd=.2;
plane{y,0 texture{Mirror} translate -kd*y}
plane{y,0 texture{Mirror} translate -kd*y rotate 120*z}
plane{y,0 texture{Mirror} translate -kd*y rotate 240*z}

// square camera
camera{
    location <0,0,-1>
    direction 1*z
    up 1*y right 1*x
}

--
Jaime

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