Walk around any major city in the world and you'll find iconic buildings that simply couldn't have been constructed until just a few years ago.

Some are so admired by the public that they've gained affectionate nicknames: two famous examples are the Bird's Nest (the National Stadium) in Beijing and the Gherkin (30 St Mary Axe) in London.

But now we're seeing some dramatic new concept buildings turning the heat up a notch. The Newer Orleans building and the incredible Kunsthaus 'friendly alien' gallery in Graz, Austria are both great examples of this fascinating new trend.

How on earth were these structures conceived – and why don't they come crashing down? Modern building materials have played their part, but the real hero of the modern skyline is the computer.

Bricks and bytes

Before computers were invented, these buildings could exist only in the minds of architects. Now, thanks to advances in computer graphics and pre-visualisation, we can explore structures before they're built.

Computers are also essential beyond the initial design stage, making it possible for engineers to analyse the stresses and strains that an architect's dream will place on steel, glass and concrete in reality. The program AutoCAD is still the dominant design application.

A veteran of Computer-Aided Design (CAD), Autodesk has been developing the program since its inception in 1982. The architectural design suite now graces the computers of almost every architectural practice in the world. Pete Baxter, Autodesk Sales Director of the Building Solutions Division for Northern Europe, says: "CAD enables architects to test and analyse designs in an intelligent and efficient way, and because this is done at the earliest possible stage, it gives them the freedom to realise their creative ideas while designing buildings that are fit for purpose."

Using pre-visualisation to clearly view the design of a new building has become very popular over the last couple of years. From the slick graphics in TV shows like Grand Designs to the fl y-by visualisations of how the main stadium and aquatic centre for the London 2012 Olympics will look once it's completed, we all expect to see pixels flying before we see bricks being laid. Visualisation has also become an art form in its own right, with companies like Smoothe, UNStudio and CityScape 3D using software such as V-Ray, Spine 3D, Maya, LightWave, MotionBuilder and Photoshop to portray their concepts in an aesthetically pleasing way.

Building with maths

Building information modelling (BIM) is a branch of architectural and engineering computation that enables all parties to design a building without having to get their hands dirty. Within AutoCAD, for instance, the BIM components include 3D digital modelling tools Revit Architecture, Revit Structure and Revit MEP for mechanical, electrical and plumbing engineers.

The Newer Orleans project is a good example of BIM in practice. The architects at UNStudio outline their approach clearly: "We design in 3D from the very beginning of each project. We also use our models to acquire data for the development of the design and the visualisation of the final project."

Many of the world's architects and visualisation specialists use tools like Bentley Architecture V8 XM, a suite of structural design and architectural BIM tools. The whole suite runs on the well-established MicroStation platform , which offers world-class 3D rendering via its Direct3D support.

The design applications that are now used in architectural practices can be as complex as the MicroStation platform or as traditional as ArchiCAD and the applications from Autodesk. They're now moving one step forward by including APIs that can be used to link any numbers of third-party applications together, allowing data to be seamlessly transferred between apps.