The letters CGI stand for Computer Generated Imagery, and refers to any visual image, whether static or moving, that has been either completely created by a computer system, or at least partly created or embellished by computers. CGI has been one of the most significant markers used to identify the developments in technology, the advances in the hardware, and the developments in software systems and those who use them.

When the idea of using images that have been created on a computer was first introduced to us in television and film, it was fairly obvious which bits were real, and which bits had been added in or replaced using a computer. Sometimes reality and the computer images were combined in a single picture, but more usually they were quite separate. However, as technology has advanced so far and achieved so much in recent years, the use of CGI has massively increased the quality of image that is seen by the viewer, to the point where today it is very difficult, and often impossible, for anyone but the experts to be able to distinguish between what is real, and what is not.

For film and television companies it is often the case that either certain shots or images can only be generated on a computer, simply because they don't exist in reality - such as living, breathing dinosaurs, or a spaceship flying into a black hole - these have to be done on a computer if they're going to be used at all. To a large extent, this capability has determined the actual content of films and programs, with producers using these tricks to embellish the storyline.

The other reason they're used is either down to cost or safety. If a building is going to explode, having a CG model of the building and having the computer create an explosion effect will still look realistic, but can be filmed from any angle, edited and adjusted over and over to get it just right, and with absolutely no danger to anyone. To do the same thing in reality would cost a fortune, be almost impossible to do repeatedly because of time and cost, and real explosions always have the possibility that someone could be injured.

So what does CGI have to do with computers? Often video games and computer games are developed alongside films and television programs, and this can often result in models and scenes being developed for the program at the same time as for the game. This results in a computer or video game which is genuinely seamless when compared to the program. It is this use of CGI across the media, and this seamlessness which increasingly means that video games are an extension of the film or program - that broadcast media is now becoming inclusive and active, rather than a mere passive opportunity.