Da Vinci dissection illuminates conception

Visual computing" is a mysterious term. No painter or computer artist simply paints pictures. Instead they understand the play between image and perception, and adjust their work so it creates the impact they seek. If they use a computer to construct the image, billions of calculations create the colours and lighting, and then as much goes on inside our heads to appreciate it. This bridge from conception to appreciation is what visual computing is about, and it is changing the world.

An important reason why the worldwide web is so successful is because it has a visual interface so that people can use it without interrupting their conscious thought processes. We understand intuitively what "drag and drop" and overlapping windows mean, which would be almost incomprehensible concepts if they had to be spelt out. Lack of appreciation of the power of visual computing, this harmony of the human perception and computer graphics, is one of the key reasons for the failure of Wap (Wireless Application Protocol).

The combination of science and art that is visual computing started in the Renaissance, when artists took to dissection to understand human forms better. They found that art is not just understanding perspective and colour, but requires a profound understanding of the human visual system. Leonardo da Vinci's study of folded cloth uses a range of pigments, yet we see uniform colour. Leonardo conjures up a three-dimensional cloth, which we can instantly appreciate without thinking about the behaviour of light or reflection from a cloth texture. Somehow our eyes and brains effortlessly understand the complexity of what Leonardo wants us to see.

We might think that we can see brightness and colour separately, but an experiment with Leonardo's cloth proves how much more subtle our vision is. If Leonardo's lightness is converted to a spectrum of colours, but of equal lightness, we cannot even see the cloth, let alone its three-dimensional shape. Yet, technically, exactly the same information is present; it is just that the way it is displayed does not suit the human visual system.

Things have moved on and the power of computing now means we can produce images that rival the impact of Leonardo's. Computer graphics can construct images whose impact goes beyond art, from imaging inside us for medicine to understanding the behaviour of stars for astronomy. While we are entertained by Walt Disney animations, scientists using the same techniques present information for tracking thunderstorms and for designing new drugs. No doubt businesses visualise the recession, and understand it better for doing so. If so, let us hope they understand visual computing, and present their analyses in ways they can easily see.

One would imagine that a book about visual computing might be lavishly illustrated with works by Monet and Rembrandt, modern brain scans and satellite images. If one further considered visual illusions and Stealth bombers, and a text that explains the principles, one might begin to appreciate Mark Friedhoff and Mark Peercy's Visual Computing : an attractive coffee-table book and one that will make fascinating reading for artists, computer scientists and psychologists. It is the sort of book that left around teenagers could stimulate career dreams, in anything from computer games to neurology. Visual Computing packs an astonishing enthusiasm into its pages with just enough detail so that you understand without being overwhelmed.

Harold Thimbleby is professor of computing science, Middlesex University.