What's the Use? by Ian Stewart

Author:Ian Stewart [Stewart, Ian]
Language: eng
Format: epub
Published: 2021-08-17T00:00:00+00:00

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Questions that very few gamers or moviegoers worry about are: How do the graphics work? How are these illusions created? What makes them so convincing? Fair enough: you don’t need to know about any of that to enjoy playing the game or watching the movie. But the historical development, the techniques that had to be invented to make it possible, and the companies that specialise in CGI and write games, need lots of highly trained people who know how the various tricks work, in considerable technical detail, and have the mastery and creativity to invent new ones. It’s not an industry in which you can rest on your laurels.

The basic geometric principles have been around for at least 600 years. During the Italian Renaissance, several prominent painters began to understand the geometry of perspective drawing. These techniques let the artist create realistic images of a three-dimensional world on a two-dimensional canvas. The human eye does much the same thing, with the retina in place of the canvas. A full description is complicated, but in simple terms, the artist projects a real scene onto a flat canvas by constructing a straight line from each point of the scene to a point representing the viewer’s eye, and marking the place where this line meets the canvas. Albrecht Dürer’s wonderful woodcut Man Drawing a Lute is a vivid depiction of this procedure.

This geometric description can be turned into a simple mathematical formula, which transforms the three coordinates of a point in space to the two coordinates of the corresponding image on the canvas. To apply the formula, you just have to know the positions of the canvas and the viewer’s eye relative to the scene. For practical reasons you don’t apply this transformation, called a projection, to every point of the object, but to enough points to give a good approximation. This feature is visible in the woodcut, which shows a lute-shaped set of dots, not the full outlines of the lute. Fine details, such as the thatch of a roof, the ripples on the river, and of course their colours, can then be ‘draped’ over this collection of points, using methods that I won’t go into because we’d need another book.

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