CGI companies specialise in producing an alternate version of reality. This can take a huge number of forms, but its probably reasonable to say that, with a few exceptions, the most impressive of these are the ones where the differences are subtle but significant. Take, for example, the Shard of Glass, the iconic London skyscraper currently under construction. Artists drawings can give some kind of impression of how this 330-metre-tall glass-covered building will impact the landscape and how it will tower over its neighbours (the Shard is the 45th tallest building in the world and the second tallest in the UK, after the Emley Moor Transmitting Station in Yorkshire). However, until a few years ago there was just no way to grasp how it would really appear in its context especially not from multiple angles and vantage points.
This is one example of where CGI companies can manage the impossible. By creating a detailed 3-dimensional representation of the section of the city desired, and superimposing data from the Shards plans, it is possible to make a life-like model of the area that can be viewed and assessed from anywhere inside it. This means that the full impact of the building can be understood both in terms of its impressive height, and in terms of any problems that might need addressing before construction actually started. Such use of CGI is vastly preferable and far superior to creating individual artists renderings, which by their nature are costly, time-consuming and restrictive.
With this use of CGI, companies can create mock-ups of their products whether architectural or otherwise and see how they will look and act (within reason) before they are actually made. The software is extremely versatile and powerful, and produces replicas of the desired product that rival photographs in their quality. In fact, it is now becoming increasingly difficult to spot the difference between a photo or artists representation and a CGI model, such is the detail of the processes used.
The process begins by forming a framework of the object or space to be modelled say, a room or internal space to be designed. This is then filled with its contents furniture, fixtures, and so on to produce a simple 3D line version of the space. After that, the fun starts. This initial rendering can be customised in limitless ways, by adding colour, lighting, texture and other variables, all virtually on the computer screen. If you want, the process can be captured as an animation, showing exactly how it happens in stages from start to finish even with music and commentary, if you want. Naturally, the whole thing takes time, and a certain amount of expense, but CGI companies are going to be able to provide you with infinite possibilities for (e.g.) interior design in short order once the ground work has been carried out; otherwise, theres no real way to know how things will look other than trial and error and thats going to be far more costly and time consuming, not to mention messy. For that reason, its often faster and cheaper than doing it in the real world.
CGI companies have just come of age, and they are really only starting to penetrate the market. The next few years are going to see a profusion of the services they offer, allowing designers a powerful tool to model their products virtually in lifelike 3D, which has huge advantages from a development point of view as well as for marketing potential. The use of CGI brings a product or space alive, without having to be physically present of for the product to exist at that stage and all to a standard that is almost indistinguishable from reality.