"Ender's Game," due on Nov. 1, is the latest film to make gravity, or the lack thereof, a challenge for its characters. The film, based on Orson Scott Card’s 1985 novel, follows Ender Wiggin (Asa Butterfield), a gifted boy sent to military school in space in anticipation of an alien invasion. In the battle room, cadets navigate zero gravity much like Sandra Bullock in “Gravity” and compete in war games organized by Col. Hyrum Graff (Harrison Ford). Here is a look at how their world is brought to life, as explained by the director, Gavin Hood (“X-Men Origins: Wolverine”), and the visual effects supervisor, Matthew Butler. — MEKADO MURPHY  The StarsThe large diamondlike metal objects that float in the battle room are called stars and are used strategically during the games, though in different configurations, depending on the challenge. The neon-looking triangles on each star sit underneath a handrail that cadets, like the one at near right, can grasp to steady themselves. Many of the stars were added digitally, but the team did build a few tangible ones. The crew built one for Ender’s friend Petra (Hailee Steinfeld) “that had a soft, rubberized surface so that we could slam Petra into it really hard for one shot,” Mr. Hood said. “But others were made of real metal.” Because the battle room scenes were often in low light, the filmmakers used the glow emanating from the stars to illuminate the actors. “There are 2,000 individual LEDs inside those stars,” he said.  The CadetsMaking it look as if the actors were weightless involved both physical and digital means. For this shot, Mr. Butterfield and Aramis Knight were fitted with harnesses, and, with the help of cables and motorized arms, suspended above the ground. The astronaut Greg Chamitoff (a former roommate of Mr. Butler’s at the Massachusetts Institute of Technology) advised the filmmakers on how to move. Even so, Mr. Butler had to digitally manipulate some of the footage to make the movement feel more fluid and weightless. “If you don’t do a completely smooth move, it can result in incorrect physics,” he said. “We stabilized the content and repositioned some of it.” Scattered around the frame are four other characters that are purely digital creations. That way, the effects artists could get the physics just right.  The EarthThe film is set in the future, but not a postapocalyptic one as far as Earth is concerned. Rather, Mr. Hood was interested in the concept of a “beautiful Earth,” as he called it: he wanted audiences to look at the planet and understand why aliens would covet its resources. “This was a dream of mine, to be able to look down and feel not only that I’m up in space but my planet is beautiful, rather than dystopian and miserable with everything falling to bits,” he said. He asked Mr. Butler and the visual effects crew to enhance the planet’s look ever so slightly to give this shot an even greater sense of wonder. The blue of the ocean grew bluer, and the sunlight reflecting on the water was heightened. “The movie has a lot of dark moments,” Mr. Hood said, “and it felt like we needed some moments of joy.”  The Battle RoomThe book describes the battle room as a square black box, “but for the movie I thought, we can’t go into space and be in a black box,” said Mr. Hood, who conceived the room’s look with the production designers Ben Procter and Sean Haworth. “Why don’t we put in a domed sphere, so when the characters jump out, it feels like they’ve pretty much jumped out into space?” This allowed for a view of Earth looming outside. But the background perspective changes with each battle game. “I really wanted to use the fact that I was in a glass dome as an opportunity to change the lighting with the mood each particular scene demanded,” Mr. Hood said. Mr. Butler and his effects team at Digital Domain worked out every computer-generated detail, down to the triangular panes of glass that compose the dome and how light reflects off them. “We had more than 300 shots in the zero-G room, so we needed to be able to build every part of it,” Mr. Butler said.
A look at the creation of the battle room for âEnderâs Game,â which required a combination of digital and physical special effects and scrupulous attention to physics.