Weta Workshop's Sentry Turret, based on the enemies from the popular Half-Life video game.

Wellington's Weta Workshop has constructed a life-size version of a robot from popular game series Portal and sent it to the US-based company behind the game - Valve Corporation.

The device was modelled on the Aperture Science Sentry Turret from Valve's Portal and Half-Life game series and is shown being unboxed and activated in a video posted on YouTube by Valve.

Valve asked Weta Workshop to create it after the Miramar company created another turret for Valve's Team Fortress game.

Weta Workshop director Sir Richard Taylor said the design was run on customised paintball sentry software and was difficult to design, because the whole thing needed to pack away and expand when activated.

"It doesn't look like much, but it really tested us - to our limits," he said.

A motion sensor detects targets and activates the turret or puts it to sleep. When a target is acquired, the turret mimics machine gun fire with sound effects and flashing lights while speaking with a soft, child-like voice.

In the game series, the Sentry Turret is an enemy which the player must avoid or defeat. For safety's sake, this version contains no live ammunition.

Those looking to buy their own turret could be in luck - but they would need deep pockets.

Sir Richard said Weta would consider making the devices for a consumer if Valve were to allow the license, but the cost could be considerable.

"It's little less pricey than a piece of military hardware from the USA Government - and a bit more expensive than a piece from the New Zealand Government," Sir Richard said.

Weta Workshop was currently working on design work for two other games, and there was potential for the company to move further into the field, he said.

"We've always held a long desire to develop our own game intellectual property around Dr Grordborts," Sir Richard said.

Weta Workshop had a friendly relationship with Valve, with some Weta Workshop staff now working for the software company, including conceptual designer Jeremy Bennett, who is seen in the video.

Valve Corporation was formed by two ex-Microsoft employees in 1996 and has since become one of the largest computer software companies in the world, notably due to its game Half-Life's success.

Its growth was accelerated by its Steam client software which allows gamers to purchase and install high-quality games via the internet, as opposed to on disc.

Half-Life 2 has sold more than 12 million copies, making it the third best-selling game of all time for the PC platform. The original Half-Life sold 9.3 million copies.