Monthly Archives: December 2010

How complex could the human brain be?


Well, here is a tiny piece of a MOUSE brain:

Researchers at Stanford University School of Medicine using array tomography imaging were able to see tissue samples from a mouse brain that had been bioengineered to make larger neurons in the cerebral cortex express a fluorescent protein (found in jellyfish), making them glow yellow-green. The glow made it possible to see synapses against the background of neurons.

According to a Health Tech article at cnet news
 (http://news.cnet.com/8301-27083_3-20023112-247.html)
there are about 200 billion nerve sells connected to one another via hundreds of trillions of synapses with each synapse functioning like a microprocessor which collectively (tens of thousands of them) connect to a single neuron to other nerve cells. In the cerebral cortex alone there are as many synapses as there are stars in 1,500 Milky Way galaxies. One synapse may contain 1,000 molecular-scale switches.  Put another way, a single human brain has more switches than all the computers and routers and internet connections that exist on Earth.

To me, this information is stunning and implies that the complexity and number of things that go on in a person’s brain is far beyond our capability to presently understand! Indeed, it is beyond belief!

When I think about the above in context with the premise that there is a lot going on when we engage stereovision… It would appear that we grossly underestimate the number of things we should be considering!

Thank you to Professor Dominick Maino for bringing this to my attention in his blog!
http://mainosmemos.blogspot.com

This information is stunning and I suspect many people just won’t give it the consideration it deserves.

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I am presenting a paper at SPIE January 25, 2011 at 5:30 PM Paper 7863-49


SPIE (the International Society for Optical Engineering)  See:
http://spie.org/x16218.xml is holding a conference on 3D imaging from Jan. 23 – 27 in San Francisco, CA. My paper and presentation: “Human perception considerations for 3D content creation” is about the problem of perception conflicts as they relate to 3D imagery and what to do about them.

I first started thinking about this when I saw an old lenticular photograph of Queen Elizabeth. The photograph could be viewed with stereopsis but the Queen looked like she was dead. Watching the movie Beowulf, while not in 3D, also gave me the creeps as the characters had a dead aspect to them. I noticed some 3D lenticular photographs of people presented with a doll-like character. I then started to notice things in 3D movies that didn’t seem right. When details disappeared into blackness or got blown out to white I noticed an uneasy feeling while looking at that part of the 3D presentation.

Indeed, every time something was presented in 3D that was atypical or not possible to see in the real world, I could detect a feeling of conflict present at some level in my subconsious and I started to manifest a sensitivity to it with regards to recognizing when it was happening.

All of these observations got me thinking about the various mechanisims that we use to see and interpret depth, space and texture. Certainly vergence is the primary mechanism, but as I became more aware of supporting clues like accommodation, motion, luminance dynamic range, binocular rivalry, field of view and so on, I came to a realization.  I realized that when non-vergence depth clues weren’t complementary that those elements or perceptions in conflict required suppression to continue viewing without some sort of physical effect occurring (typically unpleasant such as headache, nausea, etc.).

My paper is a start to the investigation of the importance of supporting perception cues as it relates to stereovision.

*Vergence is the simultaneous movement of both eyes in opposite directions to obtain fixation and the ability to see depth.

*Accommodation is the automatic adjustment in the focal length of the lens of the eye to permit retinal focus of images of objects at varying distances. It is achieved through the action of the ciliary muscles that change the shape of the lens of the eye.

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The Role of Accommodation And Seeing Depth


As I read stereo filmmaker’s blogs and read lists and group postings, the comments center around: What are the rules? What is the right camera lens spacing? How do you avoid breaking the stereo wind0w. Too much parallax? What is the right camera toe-in? If you just have the right formula, then perfect 3D can be accomplished. Everyone wants to know the right thing to do.

If something doesn’t fit that mindset, it is quickly dismissed. For example, it is impossible to simulate accommodation (the eye muscles focusing on objects at different distances) when all of the visual content is on a single plane (the screen in a 3D theater, or the plane of the printed surface on a multi perspective lenticular. Well, we seem to be able to see 3D just fine anyway–so it must not be important. 

Common sense tells me that is wrong.

Since Whetstone’s observations in the 1800’s scientists have fixated on the notion that two eyes and binocular disparity is what seeing depth is all about. Common sense tells me that it is the most important component, but only because it facilitates the supporting capabilities to fully define seeing depth – which, in the overall scheme of things is about 70% of the process in my humble opinion.

Binocular disparity (a slightly different image seen from each eye) makes us aware that depth and space exist. Without that, the other supporting depth cues are considerably weaker. Just ask anyone who acquired stereopsis vision later in life. They will tell you that things like motion parallax did not give them a sense of depth – whereas someone having stereopsis vision all their life will see depth with one eye looking out the window of a moving car.

So it is with accommodation. I didn’t really “get” the importance of accommodation until one day I was walking directly under several electrical powerlines overhead. I looked up with the power lines going across my field of view from left to right where they simply appeared as horizontal lines overhead. I could determine that some power lines were higher (farther away) than others – but NOT because of binocular disparity. In this instance, there is little, if any, binocular disparity since they are horizontal lines with little perceived texture. Each eye is seeing a horizontal line. Indeed, if I draw a left eye set of horizontal lines and a right eye set of horizontal lines, the two images (with horizontal displacement) have NO depth when viewed with a stereoscope or similar viewing device.

It wasn’t motion parallax that made it possible to see depth. It was accommodation that clearly made it possible for me to see the various heights of the different power lines. The depth cue to me was equally powerful to that of motion parallax. And accommodation solved the problem of being able to see depth where binocular disparity provided no clues with regards to the height of the power lines.

So, it is no great leap to realize that where binocular disparity becomes weak as a sense of depth, other components of vision take over to fill in the gap. Seeing 3D is a system whereby the brain uses multiple senses to perceive and interpret a scene. When one or more of the senses conflict, and that conflict isn’t suppressed, it stands to reason that people might feel some level of discomfort no different from motion sickness or dizzyness. This HAPPENS when senses conflict and suppression of a conflicting sense is not suppressed.

Over time, most people – probably all people if so motivated – can overcome and suppress conflicting sensory input. And that process is adaptable. Take people at sea… they get their sea legs and then get their land legs. For some, it happens faster than for others.

Lets jump back to accommodation for a second. When we remove accommodation from our stereopsis vision, then it stands to reason that it isn’t a good idea to present imagery whereby accommodation would play a major role in seeing depth. For a 3D motion picture – that means AVOIDING large amounts of depth in a scene – or at least large amounts where there isn’t a specific area of attention.

Wait, that means it isn’t a good idea for things to stick way out of a 3D screen!

Yes, that’s right. Especially things with a horizontal orientation. And whenever there are scenes with a lot of depth then as many other depth cues should be implemented like motion parallax to help compensate for the supporting sense (accommodation) that is missing.

Once we start to understand that seeing with depth is a system of many perceptions, then we start to realize how to be better stereographers and 3D image artists.

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