Player one: Are you ready? ; Ride a monster wave, score the winning goal in the World Cup, pull an ollie 540 on your deck - all from the comfort of your living room. Huw Williams discovers how the best sport computer games are put together... and learns the dark secrets of their creators - The Independent (London, England)

Accelerate, shifting up through the gearbox along the straight.Fourth gear, a sweeping right- hander - the back end of the WorldRally Championship Ford Focus starts to slide on the loose gravel.Drop down to third and the car bites into the turn. The adrenalin issurging through you. Keep it clean to the end of the stage and theGreek Rally is yours.

Well, it's yours as long as one of your mates doesn't walkbetween you and the telly. Last year in the UK, computer gamesbrought in more money than video sales, video rentals and cinematakings combined. And sports- simulation games (sports sims)accounted for 31 per cent of the total UK market in 2001 - they'reexpected to take an even bigger chunk this year. What makes a goodsports sim? According to Algy Williams, the managing director ofBabel, a large games-testing company, 'a good sports sim relies ondepth of game-play and true-to-life action that transforms any gamerinto an international superstar. Sort this out, and you've got awinner.' But there's one more piece in the jigsaw puzzle: the starendorse- ment. With that kind of revenue at stake, games developersincreasingly want to make sure that their product has credibility bygetting big-name stars to advise on authenticity.

Thanks to relentless media coverage, computer-game players feelcloser than ever to their favourite sports, and don't like it when asport sim gets a telling detail wrong. Of course, for themanufacturers, a well- handled endorsement is a licence to printmoney. One of the most popular sports sims is the Tony Hawk's ProSkater series, which has sold 15 million games worldwide since itslaunch in 1999. Sure, the game plays well, but more than that, youget to play one of the world's most famous skateboarders and notsome generic pixellated dude. The fourth edition of the skateboardgame comes out in November and, as with the earlier titles, Hawk hasbeen involved since day one. 'The first game was the most gruellingprocess because you're starting from nothing. But they had a basicengine [software] with a skater and I could tell they were on theright track,' he says. 'We do motion-capture filming of me on a deckdoing a trick and film tricks from a few different angles. Then wechoose what works, and what locations and skate spots to use. I geta version, I play it, make suggestions, they have ideas and a lot ofemails go back and forth. After the first game, they got into agroove, learned a lot and it became a lot easier to convey how tomake it cool, how to make it legitimate.'

The 34-year-old Hawk may now be in the twilight of his careerbut, thanks to the game, he is more famous than ever. For histroubles, what's more, Hawk is reputed to earn several milliondollars a year from his endorsement of the game.

Pro Skater's popularity was unexpected but its manufacturers,Activision, have been quick to capitalise on the popularity ofadventure sports. A computer-rendered line-up, below left, of thestars they've signed up reveals the biggest names in action sports:Tony Hawk, BMX king Mat Hoffman, Snowboard X-Games gold medallistShaun Palmer, pro surfer Kelly Slater and wakeboarder Shaun Murray.

But the game developers try to get their money's worth from thestars they sign up. Colin McRae regularly tests the rally games thatbear his name - the latest, eagerly awaited version, Colin McRaeRally 3, is out this September and will be the first editiondesigned for the new-generation consoles (Sony PlayStation 2,Microsoft Xbox, Nintendo GameCube). McRae has been sent prototypesover the two-year development period, playing the game and givingdetailed comments on how the car handles throughout the courses.

Getting the pros to assist the process is a significant assetaccording to Guy Wilday, the game's studio chief at the company thatdeveloped it, Codemasters. 'They [McRae and his co-driver, NickyGrist] are two of the very few people in the world who can do thisfor real,' he says. 'They're not just figureheads, they are veryenthusiastic and a major part of the development team. They reallyput the hours in.'

The role in the game's development of Grist is a case in point.His detailed spoken instructions get McRae around the actual WorldRally Championship courses swiftly and safely, and he provides asimilar service in the computer games, calling the corners andvoicing the descriptions of each stage. For the game's thirdincarnation, Grist has been still further involved. He was upsetthat games players thought there were a couple of bad calls in theearlier versions, so this time he has written pace notes for theentire game, much as he would for McRae.

The American surfer Kelly Slater, a new recruit to gamesendorsement, was similarly attentive in the development of KellySlater's Pro Surfer. 'I've been involved in it at every level. Fromhelping to pick the other surfers that are in the game and workingto perfect their style, choosing the beaches, helping shape thewaves, making sure the manoeuvres were accurate and choosing themusic.'

Sometimes, games developer and sportsmen work even more closelythan that. Codemasters are working on their new football title ClubFootball, featuring 15 of Europe's top clubs, including Arsenal,Manchester United and Aston Villa among other British sides. Rivaldevelopers Electronic Arts currently set the standard for footballsims with their Fifa Football series, thanks to a licensing dealwith Fifa. To compete, Codemasters went to the top European clubsdirectly and got the sort of information that the media would killfor.

Club Football isn't due to hit the shops until November but theyhave already been tipped off about which players, subject to injury,are likely to be in next season's squad for each side. According toSimon Prytherch, Codemaster's studio master for Club Football, 'Weknew back in April that some players would definitely not be in nextyear's squad. And so we didn't include them in the game. When a newsigning is in the offing, the club will call and arrange for us toget his details way before the press get hold of who it is.'

The result of this unprecedented level of collaboration isanother feature of sports sims - an ever-more-impressive level ofthe sort of authentic visual and aural detail that contributes tothe atmosphere, the texture, the feel of a sport. Here's an example:as well as owning Club Football, you are a season-ticket holder forLiverpool FC - why not review the goal you've just scored in thecomputer game from the very seat you take every other Saturday atAnfield? And as you celebrate your virtual goal, you can sing alongto chants heard on the Kop itself.

So far, so amazing. But do game developer and game ever get alittle too close? Perhaps. 'Sometimes we've been to take photos ofplayers at training grounds,' says Prytherch. 'Later, we've had amessage from the club saying that it's not worth processing acertain player's data...' Game On, an interactive video-gameexhibition, continues at the Barbican Gallery, London EC2, until 15September. Booking is essential; for tickets, phone the box officeon 020 7638 8891. Next week: are you ready for the Tough GuyChallenge?

The games

Colin McRae Rally 3 Similar format to the last version but withvastly improved graphics. As close as you can get to the real thingwithout feeling car-sick. (PS2, Xbox).

LMA League Manager Strategy game where you do the top job at oneof 700 European clubs. Work through the trials and tribulations of aseason; buy players, select a team, and decide tactics. (PS2, Xbox).

Kelly Slater's Pro Surfer Looks beautiful and plays well. Chooseto ride waves at many of the world's best spots. Even if you hatethe water this could make you a soul surfer. (PS2, Xbox, GameCube).

Tiger Woods PGA Tour Latest incarnation of well-received golfsimulator. Play on 14 world-famous courses as one of 17 PGA pros.(PS2, Xbox, GameCube, PC).