Linear perspective is one of the least sung but most pervasive innovations of the Renaissance.

Conventionally attributed to a mixed media demonstration by the architect Brunelleschi, who left no physical evidence of the event, it was then cast into rules in the work of Alberti in 1435. Although influential writers like Panofsky have proposed elaborate accounts as to how and why it took the early Renaissance to implement linear perspective in graphic arts, few seem to have faced up to its greatest paradox.

As far as anyone can tell, the human eye and the yet more wondrous visual cortex of the brain have not changed in the half millenia before or since the 15th century. Mediaeval, renaissance, and modern artists (and everyone else with ‘normal’ vision) have seen the same linear perspective in real life, irrespective of whether they understood it, or employed it in their pictures. In this respect, it is no different from many other visual details such as shadows, and the body proportions of infants, that have also undergone radical change from their early stylised forms to later accurate representation.

Renderings of the metaphorical desktop components in computer GUIs have had a much shorter but not dissimilar history.

Original graphical interfaces, such as prototypes developed at Xerox’s Palo Alto Research Centre (PARC) and those in classical releases of Mac OS, have been comic-like in their simplicity. Before the advent of colour in System 7 (1991), the Mac had a clear black-and-white interface with windows and icons that seem crude by comparison with Mac OS X. Although colour livened up the Finder, graphic devices remained spartan in their simplicity until late 2000, as illustrated in the screenshots accompanying my -14 series of articles (here and here).

Components in the interface have become progressively more ornate. Radio buttons started as crisp circles, gained shading, and now give the illusion of limited depth. Windows, once outlined primitively, have shaded elements and appear to cast shadows on the objects underneath.

But compared with most custom desktop images, what lies on top of the desktop remains very shallow, certainly no deeper than the flat-screen display that holds the whole simulacrum. Polished and advanced the Mac interface may be, in historical terms it has yet to see its Renaissance.

Thankfully the visual cortex in the brain does not have any trouble switching between the perspective of the physical world, that depicted in a desktop photograph, the thin illusion laid on top by the Finder, and windowed renderings of 3D applications that might form our most immediate focus.

How the likes of Brunelleschi or Alberti would cope with this riot of projections is harder to predict; but with the same neurological equipment, there is no reason to believe that they should not do as well as we, once they had overcome their initial geometric shock.

There have been experimental interfaces that have conjured up greater depth, and presented projected objects instead of flat layers. The closest that Apple has come to these (in public, at least) is in the Star Trekkery of Time Machine.

SpaceTime3D was promised for the Mac in 2008, but doesn’t seem to have made any headway with Windows; it applies a similar deep space metaphor to browsing and searching. Tactile 3D (also Windows only) has sadly become too obsessed with the trappings of science fiction to stoop to being a mere human interface.

Marc Moini’s 3D fileSpace visual file system is interesting but still seems clumsy to use, and has not proved popular among Mac users.

In the 15th century, linear perspective generated a prolonged orgiastic period of architectural drawings and paintings, celebrating that new frontier of the time. It is only appropriate that these current experiments with 3D interfaces (except 3D fileSpace) invoke images of space, today’s frontier, as every Trekkie will assure you.

Perhaps OS X 10.11 will start transporting us to the next generation of interfaces, in which better use is made of this Renaissance innovation. Far from making the Old Masters turn in their graves, I think that they might be quite enthused.

Updated from the original, which was first published in MacUser volume 25 issue 04, 2009.