WHO, WHAT, WHY?
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A couple have divorced after the wife saw the husband having online sex in the virtual world of Second Life. So how do avatars have sex?
Characters interact socially
Wife walks in and finds husband in a compromising position on the sofa with another woman. Wife feels betrayed. Wife files for divorce. Marriage ends.
It's a familiar scenario in soap operas, but for one married couple it was all too real. Sort of.
Amy Taylor and David Pollard met in an online chatroom in 2003, got married and shared their interest in Second Life, a virtual world in which users create avatars to interact with each other.
But the marriage ended after Ms Taylor's online character saw her husband's avatar having sex on a sofa with a female prostitute.
First characters need to buy genitals
Male characters can get aroused and have intercourse with female ones, but graphic depictions are very rudimentary
Intercourse is usually represented by an animated sequence
So how do computerised characters have sex?
"First you need to buy genitals," says technology journalist Adrian Mars, explaining the process in Second Life. "You start off with no genitals and then you buy some. These objects can do all sorts of things. You can have ones that ejaculate at the right moment.
"But there's not much in the way of exciting mechanics. What you see on the screen is what you get and the best you can hope for is a bit of sexual humour, although some people do have intense relationships.
"Obviously the sex is not the same as in real life, but you're still expressing yourself in a way that would, maybe reasonably, upset a partner."
Participants can verbally communicate by voice or by typing speech that appears in a bubble above their character.
And although they can use the mouse and keyboard to move their character and pick things up, he says, the on-screen graphic depiction is very rudimentary. Undressing another character without their consent is not possible.
"You can touch and jiggle about a bit and you can emote and gesture in a way the other person would see. And you can have intercourse."
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Users can make their avatars sit, lie or stand for sex, says Kieron Gillen of gamerzines.com, but the intercourse is usually an animated sequence triggered by a click of the mouse on an interactive "node", although it depends how they are programmed.
"People customize their avatars with animations and enormous e-phalluses which you can buy. It's a player-generated economy and people exchange things they have created - someone builds it, someone buys it and someone puts it into action."
For people participating in this, he adds, the sexual chat is more important than the avatar having sex, which acts more like a prop to get their imagination going.
And you can forget any notion of sensual touch. As crude, pixelated representations of humans, avatars can't flex individual muscles, says Gabby Kent, a lecturer in computer games at the University of Teesside.
It would just resemble two clunky-looking characters rubbing their bodies against each other.
These kinds of online worlds are navigated fairly intuitively, she says, so just by clicking on a door could make your avatar walk through it, without the need to move your hand to find the handle.
In a similar way, some games could just have a special sequence cutting in to represent sexual intercourse. But even those offering the characters more control are unlikely to look very real. Yet that doesn't mean it's harmless fun.
"In Second Life, all the characters are real people somewhere in the world and that's why there's always such betrayal felt," says Ms Kent.
One blogger writing about his experience in Second Life describes the range of male genitalia on offer to buy, including skin colour control, sound, animations, ejaculation, urine and some that are touchable by other players to lead to arousal.
He visited virtual sex shops and sex clubs where he saw people having sex in a number of different ways.
It is only to be expected in a world where players pick every detail of how their avatars will look, says Mr Mars.
"You can design any object. You can buy your own antlers, for instance. Sex has become a big thing [in Second Life] but I suspect it's full of teenagers, so that's no shock."
Some Second Lifers have been known to misbehave - a US journalist was attacked by flying penises when conducting an interview in his virtual office.
And infidelity is not the only thorny ethical issue thrown up by virtual sexuality - some players have had sex with animals.