Whipping up a classic British storm on screen

The special effects teams have been hard at work on The Avengers movie.

STEED AND Mrs Peel defined Britain in the Sixties: modern yet traditional; stylish; imperturbable; the definition of cool. As The Avengers, they became British television's biggest ever export, selling to 120 countries. Now they are back - on the big screen from this Friday.

This time the roles of Patrick Macnee and Diana Rigg are taken by Ralph Fiennes and Uma Thurman, but the style remains the same. Achieving it has become a lot more costly, however. Where streets were always deserted because they needed to save money on extras, the movie-makers have turned to computers to achieve the same effect.

Besides digitally removing people, traffic (except for Steed's Bentley and the occasional 1930s London taxi) and the cranes working on London Underground's Jubilee Line extension, the special effects computers have been enhancing the weather.

This is because the movie's plot revolves around the country being held to ransom by a larger-than-life, Bond-type baddie, Sir August de Wynter (Sean Connery), who can control the weather. Of the 250 or so special effects in the movie, the most spectacular include tornadoes roaring up the Thames and smashing through Lambeth Bridge, the view from inside a lightning bolt and a bonsai tree going through all four seasons in 20 seconds in de Wynter's museum of weather.

With so many effects to do, the director, Jeremiah Chechik, turned to three of the UK's leading effects houses: Cinesite, which spent a year working on more than 140 digital effects shots; the Computer Film Company (CFC), which did 40 effects; and the Magic Camera Company, which not only did 65 digital effects shots but also created many miniatures (including de Wynter's lair and a snowbound Trafalgar Square) and physical effects for the movie.

"The Avengers is an action-packed movie, with a lot of green-screen composites, people hanging off wires, weather effects and digital matte painting," says Angie Wills, a producer at the Magic Camera Company. It is one of the few companies anywhere that can do all types of effect (physical, digital and models) under one roof. "That's why jobs like The Avengers or Lost In Space [where they also did a huge number of effects, including the opening space fighter sequence] are tailor-made for us."

It did an assortment of animation effects on the British-made Quantel Domino, a complete digital film production system that "is particularly useful for the more complex tracking shots", says Wills. It also did many green-screen effects (where an actor is shot against a blank background and digitally inserted in the final scene) on Silicon Graphics Unix workstations using Avid Illusion software.

At CFC in Soho, it took several months of research to discover how to create weather effects they could control precisely without losing the chaotic and organic nature of weather. Because the storms were to be seen from different angles and moving cameras, they needed to be very complex and had to be three dimensional, with lots of lightning, snow and shadows across the city as the storm moves in. This meant creating 3D models of parts of the city "so that as clouds come over, the shadows creep across the architecture," says Sharon Lark, CFC's visual effects producer. "This meant a lot more work, but is very, very effective." The clouds were built up from multiple layers and some shots took up to 80 passes through the computer.

The climax of the storm includes the destruction of Big Ben by concentrated lightning, an effect which combines models and physical pyrotechnics done at the Magic Camera Company with storms and lightning added at CFC.

Nearby at Cinesite, they were unleashing devastating tornadoes on London, the biggest of which heads up the Thames towards Parliament, smashing through bridges. It was created using the new Alias Maya particle system, with seven separate layers of particles, such as water spray, wrapped around a cylinder animated with twists, changes of speed and direction, then had it smash into a computer-modelled bridge. "The tornado has physical properties and rotates at a certain speed, so we were able to tell the computer to affect other things which it whipped off the bridge (such as lampposts), so it self-animated. This saved us a lot of time. Rather than having to individually animate more than 100 objects, we only had to do the largest objects by hand," says Alex Bicknell, senior digital effects producer at Cinesite.

One nice sequence shows a glass globe within which a bonsai tree goes through four seasons every 20 seconds - growing, shedding its leaves and being covered with snow. This happens during a camera move, which made it more difficult, in a living museum of weather curiosities. It was produced by Cinesite using Maya/Dynamation particle systems for the snow and Alias Wavefront for the tree modelling and animation.

"A lot of work we did was digital matte painting, to get rid of traffic and people. It had to look deserted," says Bicknell. This included creating several unique London locations, such as where Steed drives under the Thames to Mother's office. In reality, Ralph Fiennes twice drove into the entrance to an old underpass near Holborn while the traffic was stopped for a few minutes on either side of the street. Combining the two shots it looks as if the street is deserted. To this was added a view of the river at Greenwich and large government-type buildings.

One of the longest effects sequences in the film (with more than 40 shots that took five months to complete) sees a swarm of remote controlled Bee-copters (four-foot metallic bees armed with gatling guns and explosive stings in their tails) attacking Steed and Mrs Peel as they drive to Sir August's mansion in her E-Type Jag. Originally, this was intended to be mainly done with model bees, "but they didn't work as well as the computer- generated ones," says Bicknell. Instead, the models were used mainly for reference, such as being walked through the set so the 3D animators could see how the lighting conditions affected the metallic surface. The bees required so much work because they have six legs jointed in three places, pneumatic pincers, a six-segmented thorax which can rotate and swivel, and a head that can move, as well as rotors.

Because the actors were shot on location, from helicopters and cranes, Cinesite had to use motion-tracking software to fix the animations to the live action. There were also lots of physical pyrotechnic effects used during the chase, such as shots and explosions, including some where nine bees crash into a low bridge. "It was a great release to us every time we had an explosion, because it meant we had one less bee to animate," Bicknell says. The 3D renderings were composited into the live action on Kodak's Cineon system. Animated shadows give extra realism, and tracer fire was added to coincide with bullet hits on the road, as were the "stinger" missiles let off by the bees compressing and releasing their thorax.

Cinesite also did a lot of what are now "bread and butter" effects, such as inserting video graphics into shots of computer monitors. "It has become so easy and quick that there is not much price difference between shooting live or doing it in post-production. However, post is much more flexible, as it is easy to replace the shots at the last minute," Bicknell says. It also means that the director doesn't have to worry about timing the shot to hit a particular mark in the graphics and can concentrate on the actors instead.

One effect to watch out for gives us a glimpse of "Invisible Jones", the non-entity at the Ministry, as he walks in front of a slide projector. See if you can recognise the famous actor playing the cameo role in the subtle, semi-opaque glass character reflecting the light.