Wired on Friday: The photographs are shocking. It's the same shock as I felt when I saw the first smooth, glossy, Platonically perfect three-dimensional computer graphics. It's that little jolt you feel when seeing a new computer-generated animation at the cinema.

You know it's all fake, but the new images are so much closer to reality than previous efforts: the Titanic, the Imperial Senate, the dinosaurs. The novelty temporarily suspends your disbelief for you.

Only when the next photorealistic innovation is unveiled do you spot the warts and blemishes in the old animation techniques, and the formerly dazzling films seem suddenly awkward and unreal.

This time, it's not at the movies. It's a photograph, uploaded online to a discussion board (you can see it at http://tinyurl.com/cu4r7 ). In it, some sort of bipedal battle robot stretches up on its legs to survey a house. Its metal armour gleams in the setting sun. The robot is recognisably transplanted from Half-Life 2, a popular and highly detailed computer game for PCs. What gives this picture the shock of the new isn't the towering power of the killer robot. It's that the 10-foot droid is clearly in some fan's messy front yard, somewhere in deepest American suburbia.

Here's what happened. Some young fan plucked the model of the robot from the game he regularly plays, and loaded it up into a 3D drawing program similar to those used by computer games' animators to sketch their ideas in simple solids. Then he walked outside, and placed a mirrored sphere about the size of a football in the middle of his yard. He took a photograph of the mirrored ball and surroundings, capturing both the scene in his garden, and - through the image reflected in the ball - all the sources of light that surround the garden. The red setting sun, the glare from a nearby car, light bouncing from pavements, and clouds, and the green of the grass.

Feeding that photograph back into the 3D software, via another piece of dedicated software called High Dynamic Range (HDR) Shop, was all that was needed for the computer to imagine and display how the robot might look, dropped into the fan's neighbourhood, lit by the same light sources. Shadows are placed correctly: dim images of the fan's run-down bungalow are reflected in the bug-eyes of any aliens he drops into the scene. The result, to my eye at least, is far more eye-opening than the game.

Just as a horror film is all the more sinister for its suburban setting, these images stand out because they're so much closer to the fan (and therefore to the viewer). And then, of course, after you've experienced that shudder, the next step is to want to stick the creature in your own family snaps.

At some point, someone will work out how to make money at this. The simplest kit for preparing HDR models would be a common-or-garden digital camera and a metallic inflatable balloon. Throw one in a games package, and you could have children playing an action game chasing killer robots and exotic aliens around their own neighbourhoods.

And if dropping the exotic armour and weaponry of a shoot-'em-up into a picture of your neighbourhood isn't personalised enough, how about really dropping that robot into the yard?

Modern video technology has enough smarts to only need the 3D blueprints - of, say, a lunging alien - to display it. It will colour it, work out the shading, and place it before or behind other 3D virtual objects.

The advantage for games programmers is that rather than calculate the colour of every dot on a monitor, they can just send the video card a string of raw blueprint instructions. The code tells the video card the gun is made from a cylinder this high, this wide; it supplies a torus for the trigger guard, a bisected plane for its gun-sights. Colour it grey; show it onscreen; rotate, and zoom.

Ingenious games-players are now using HijackGL, which sits between these 3D games' programs and the video cards. They receive those designers' blueprints - and output the same blueprint in code compatible with computer-controlled lathes. The lathe follows the same recipe - a cylinder, a torus, a plane. Instead of displaying the gun, it is sculpted from plastic on the game players' desk.

Before the tabloids fret, this is of course is not a working gun. Just as a phaser from Star Trek can't fire death-rays, this is just an empty prop. And computer-controlled lathes are not on many teenagers' Christmas list. Not at $3,000 a shot second-hand, they're not. But prices plummet, and dedicated fans, eager to inch a little closer to the imaginary world of their favourite games, learn to pluck items from the virtual world and drop them into their own. And some intriguing questions emerge.

This is all, at heart, a form of copyright infringement. That photograph, that artifact, is a form of a derivative work. But what games company in their rightful mind would pursue such dedicated fans?

Perhaps these aren't copies, but rather the fun escaping into the real world.