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Bifocal Displays: Farsightedness on the net?
by Juan C. Dürsteler [message nº 3]

The idea of bifocal displays is not a new one. Back in 1982 Bob Spence and Mark Apperley proposed to separate what is in the focus of our attention from the elements the lie on the periphery of the same, maintaining both in our field of view.

One year before, George W. Furnas, at that moment at Bell labs, suggested the “fisheye view” in order to obtain the same result: that the trees do not avoid you seeing the forest, without losing sight on both of them.

Since then, many variations of this main idea have appeared. In their excellent book Readings in Information Visualization; Using Vision to Think, Card, Mackinlay and Shneiderman group this variations in the chapter “Focus and Context”.

A particularly interesting and more recent case of this strategy is the representation of hierarchies (directories, trees, etc.) in a 2D space of hyperbolic geometry.

This type of representation, that inspired M.C. Escher in some of his famous pictures, gives an intuitive vision of the contents and complexity of the hierarchy represented.

An example of this is Magnifind , an alternative Windows navigation tool freely downloadable at Inxight’s web site.

The goal, in any case, is to represent vast amounts of information allowing the detailed visualisation of what our centre of attention (the trees) is, maintaining the rest of the context visible in a schematic but recognisable way. 

To understand the concept better it’s worth playing a little with Magnifind or looking at the hyperbolic map of the web if you don’t have the time to download it (requires Java).

A similar strategy is that of TheBrain that also offers a free of charge "Personal Brain". With it you can organise and browse your personal files and “thoughts”. TheBrain does not use hyperbolic geometry.

The most exciting thing about all of this is the analogy with the way we humans see* the world. In order to read a book we need to scan each and everyone of the words, since to see an object clearly we have to look straight at it.

If we aim at the beginning of a line and we fix our vision on that point without moving our focus from it, we’ll see that we are unable to read, or even perceive the letters that are at the opposite side of the line.

Our eyes perform a continuous scan of what is interesting for us in our surroundings. The brain builds then our perception of the world in a way that makes us feel that we have both focus and context present at the same time; the feeling of seeing the surroundings as a whole.

It’s very possible that in the near future we will see different paradigms to the traditional browser window, with new forms of visualisation that will exploit more deeply the natural ways of human perception.

More on the future of the Browser in the forthcoming messages.

* Brief appendix on vision

As we’ll probably remember, the retina has two types of cells: rods and cones. Each cone is directly connected to the brain, sending its whole information to the brain. Rods are connected to intermediate cells that integrate the signals of several other cells into a signal that is finally sent to the brain.

This fact creates a dual kind of vision: foveal vision and peripheral vision. Foveal vision is produced at the fovea, a zone with great cone density and very low rod density. The fovea is responsible for the clear, detailed vision. Peripheral vision is produced at the rest of the retina, where rod density dominates over cone density. The integration of the signals in this zone gives low-resolution vision, but allows the perception of the context.

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