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Optical Illusion

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What about this picture makes the optical illusion work?

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Maybe the fact that your brain wants to see the top beam in front, but it is drawn behind the back beam, so your brain is fighting the visual cue.

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opt.jpg

It's the shading, which allows the circled area to look like the beam that should be in the back is actually in front of the horizontal beam at the top.

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Maybe the fact that your brain wants to see the top beam in front, but it is drawn behind the back beam, so your brain is fighting the visual cue.

But what aspect in the picture makes my brain "want" to see it that way?

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opt.jpg

It's the shading, which allows the circled area to look like the beam that should be in the back is actually in front of the horizontal beam at the top.

In what way is the shading wrong? When I look at the top vs. bottom horizontal supports, and the front vs. back horizontal supports, the shading looks the same. Is there some subtle difference I'm missing?

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opt.jpg

It's the shading, which allows the circled area to look like the beam that should be in the back is actually in front of the horizontal beam at the top.

In what way is the shading wrong? When I look at the top vs. bottom horizontal supports, and the front vs. back horizontal supports, the shading looks the same. Is there some subtle difference I'm missing?

The shading is consistent and makes the beam appear as if it should be in the rear of the cube. The paradox is that it covers the front top beam, implying that it's in front of it. Shadows and overlapping are both cues we use to judge distance, and should never contradict each other. Actually they don't here either, because there is no three dimensional object there projecting shadows. The real illusion is that we see such an object, even though the medium is flat. It's the illusion of three dimensions that allows for the paradox.

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Shadows and overlapping are both cues we use to judge distance, and should never contradict each other. Actually they don't here either, because there is no three dimensional object there projecting shadows. The real illusion is that we see such an object, even though the medium is flat. It's the illusion of three dimensions that allows for the paradox.

Yes.

It's the fact that this 2-d representation of a 3-d object uses shading (differences in color or intensity) to give the illusion of 3-d that allows for the optical illusion. You could say that the "correct" representation, below, is really also an "optical illusion"; it's the illusion of three dimensions in a 2-d drawing.

fix.png

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Maybe the fact that your brain wants to see the top beam in front, but it is drawn behind the back beam, so your brain is fighting the visual cue.

But what aspect in the picture makes my brain "want" to see it that way?

I thought you were quizzing us and you’d have the answer. :D

I can't answer with precision, because I don't know exactly what the brain is doing mechanistically, but you know how when you look down railroad tracks the rails appear to be getting closer together? That perspective effect is used on paper to give images depth, but on paper it is a trick, because there is no real depth. On paper you can you can ignore 3D perspective and draw things in other ways. You might be able to do the same thing with the 3D object, so long as the object is looked at from one vantage point (witness the Parthenon in Greece, which was designed that way), but it is not the norm in nature. Our eyes and brains have adjusted to nature, because that's where we live.

This may dovetail with something I've noted about 3D immersive environments.

There are efforts out there to create full 3D immersion environments using computer graphics, where each eye gets an image of the scene from a different perspective, however while they can provide a pretty good 3D immersive effect, it's not good enough yet, because everything in the scene is on a flat display and has the same resolution, which is not the way we see things in 3 space. When we look here or there, we need to focus and adjust our eyes according to the distance of the object from us. You've trained your eyes to do that from daily experience. In a 3D immersive environment this continuous refocusing is not necessary -- everything is the same distance and requires no refocusing -- which actually puts a strain on the eyes, because it's a difficult adjustment to make.

So, in that case it seems to be a matter of how the brain has been trained.

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Yes.

It's the fact that this 2-d representation of a 3-d object uses shading (differences in color or intensity) to give the illusion of 3-d that allows for the optical illusion. You could say that the "correct" representation, below, is really also an "optical illusion"; it's the illusion of three dimensions in a 2-d drawing.

Don't forget perspective. This is probably the strongest visual cue for a static scene.

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So, to summarize in my own words, the illusion is created by the expectation of my brain of perspective in the object, which is not a real 3D object but a 2D object. The expectation of perspective is due to the fact that that is how my brain is used to seeing things in space. As far as the 2D drawing goes, there is no real optical illusion. If I were to eliminate shading from the drawing, all I would see would be a geometric pattern of intesecting rectangles.

Would you all agree?

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I'd agree with that. The shading simulates the shadows cast by shapes. Incidentally I think you might actually be fooled that an image on a photograph was a 3d object if the shadows were consistent with surrounding objects. Of course if you moved you'd see that it was a flat surface. And obviously the image would have to appear as if it was life-size. You'd never confuse a 5 x 10 photo of a friend propped on your desk with the real thing.

It might also be possible to create a 3d version of the paradox cube, if in the right conditions. You'd have to create artificial shadows that fit the light source, and it would only work from that angle, though.

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I'd agree with that. The shading simulates the shadows cast by shapes. Incidentally I think you might actually be fooled that an image on a photograph was a 3d object if the shadows were consistent with surrounding objects. Of course if you moved you'd see that it was a flat surface. And obviously the image would have to appear as if it was life-size. You'd never confuse a 5 x 10 photo of a friend propped on your desk with the real thing.

It might also be possible to create a 3d version of the paradox cube, if in the right conditions. You'd have to create artificial shadows that fit the light source, and it would only work from that angle, though.

Yes, I think you could, but it wouldn't work from every angle.

Ever see a forced perspective room, aka Ames room?

Or, try this optical illusion art:

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I'd agree with that. The shading simulates the shadows cast by shapes. Incidentally I think you might actually be fooled that an image on a photograph was a 3d object if the shadows were consistent with surrounding objects. Of course if you moved you'd see that it was a flat surface. And obviously the image would have to appear as if it was life-size. You'd never confuse a 5 x 10 photo of a friend propped on your desk with the real thing.

It might also be possible to create a 3d version of the paradox cube, if in the right conditions. You'd have to create artificial shadows that fit the light source, and it would only work from that angle, though.

Yes, I think you could, but it wouldn't work from every angle.

Ever see a forced perspective room, aka Ames room?

Or, try this optical illusion art:

Fascinating. The visual perspective is used to counteract the physical changes in dimension.

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.

Laure:

Your respresentation correctly shows the geometrical

structure that is agreeable to the mind.

Paul's Here has attempted to get us to concur that the

illogical arrangement is the superior. The key fact is

that the elements are out of place, and you have

shown us the correct placement.

Paul's Here has foisted the visual ir-representation of

the cube structure in order to shock the viewer, or

otherwise to engage his mind to get the viewer to

somehow accept the illogic as the norm. That principles

do not govern in one's sense perceptions of the

evaluation of the facts.

The goal of that method is the interference with or

destruction of the mind and/or is proper workings.

That is the expressed goal of the Surrealists as given

in The Surrealist Manifesto, I believe. That was by

Madam Blavatsky, Salvador Dali and others, I believe.

Destruction? Lets use Ayn Rand's idea that,

paraphrased, "one should always take the artist says

at his word."

Does the ir-representation "work"? No.

The emotions from sense perceptions function to give

one a read-out of the general state of percepts. For

example, there is a felt akwardness upon seeing the

arrangement given. Next it would seem that there is

something askew, even if one cannot identify exactly

what is there.

On the other hand, right geometrical and proportional

arrangements give one the sense that everything is

believable, knowable, and reliable even when one is

aware but unknowing of the principles used to

construct the arrangement.

For example, the complicated geometry and

proportions that govern the design of the Parthenon.

That is the reason for the success of designs that are

made using the principles of proportional harmony.

The correct proportions are perceived and the mind,

rather than finding the design faulty, will find it

ordered or beautiful, for example.

The term "work" is a conventional Pragmatist con-word.

I'd avoid it in a discussion of Objectivist philosophy.

Design schools often use the term, "does the design

work?" to refer to the overall integration and acheived

purpose of the design. Sometimes they mean that the

design is a good design according to the universal

principles being taught.

It doesn't mean that the design was made, qua

Pragmatism, as an action expression without theory

or expressed, shall we say, Objective, causation.

Result? It isn't funny.

Ralph Hertle

.

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What about this picture makes the optical illusion work?

A two-d projection does not uniquely map back to a three-d structure. Or putting it differently for a given two-d projection there may be an infinite set of three-d structures that will have that projection.

Shading provides what my be false close to the actual three-d object.

Bob Kolker

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TFFARF:

I don't know how to edit my posted remarks, however,

I found one of possibly many errors that may be set right.

For example, I found an error in the statement I made:

.

It doesn't mean that the design was made, qua

Pragmatism, as an action expression without theory

or expressed, shall we say, Objective, causation.

.

I should have added one word, "without":

"It doesn't mean that the design was made, qua

Pragmatism, as an action expression without theory

or expressed, shall we say, without Objective causation."

Ralph Hertle

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It's because we're scanning, not actually looking. Our brains have optimized how to look at stuff and get just enough information to move on and no more.

When my eyes hit the image I look at a few of the corners, glance at the texture of the thing and move on.

I think a lot of these illusions tie into what automatic algorithms our brains have already. 'Hardcoded' by our genes and not available to be learned or forgotten.

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