'Pacific Rim' Featurette Goes Inside Guillermo del Toro's 'Torture Machine' (Video)

Pacific Rim Hunnam Kikuchi 2 - H 2013
<p>Pacific Rim Hunnam Kikuchi 2 - H 2013</p>   |   Warner Bros. Pictures
In a new clip, the director explains why he built the heads of the robots rather than depending on CG.

How do you bring giant, 25-story-tall robots to life?

A new featurette for Guillermo del Toro's robot versus monsters epic Pacific Rim has debuted, giving us a behind-the-scenes look at how the larger-than-life robots were created for the film.

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The upcoming sci-fi action film, from Legendary and Warner Bros., follows a group of humans who have been enlisted to pilot giant robots in hopes of defeating the monster-aliens that have risen from the sea. It stars Charlie Hunnam, Ron Perlman and Idris Elba. 

While CG was definitely used to create the  "kaiju" (aka sea monsters), del Toro reveals that a lot of the robot work depended on real-life structures and machinery.

Del Toro says that the heads of the robots -- which contain the two human pilots -- were built four stories tall and connected to a contraption that could move the heads around and drop 15-feet to simulate when a robot fell.

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When piloting the robots, the actors were actually suited up inside the "head" of the robot, rather than relying on green screen.

"The easiest thing would have been to put green levers on their arms and their back and their feet and have the actors have complete free movement, but I felt you needed something with resistance," the director says in the clip.

And on top of all that machinery, water was shot at the actors as they attempted to navigate in their suits.

"I invented a torture machine," says del Toro.

Pacific Rim opens in theaters on July 12.

Watch the new featurette below.