The visual effects design team behind one of the most memorable scenes in Gravity have shared the story behind the computer-generated sequence, creating a virtual space station to plunge into the Earth's atmosphere. Most of the Sandra Bullock and George Clooney blockbuster involved CGI, but Rising Sun Pictures was forced to mix science and speculation to get the scene where the Chinese space station is knocked out of its orbit.
In the movie, Sandra Bullock's character tries to use the Chinese Tiangong station's re-entry pod as a lifeboat back to Earth, after a sudden flurry of space debris cripples the Space Shuttle and pods on the ISS. Further collisions cause the station to break up dramatically on re-entry, however.
It was always going to be an action-packed scene, but the job for the RSP team was made harder since nobody really knew what it would actually look like. "We all have an idea of what happens to a spacecraft as it enters the atmosphere," company co-founder and supervisor for visual effects on the project says, "but no one has witnessed such an event from the outside at close proximity."
The goal was something as scientifically plausible as possible, given the degree of data available. An initial 3D render of Tiangong was bolstered by extra modeling of individual parts, so that each could be shown getting affected by the physics model.
Some sections were designed to ablate and burn up - complete with a best-guess of how plasma waves might appear around them - while others crumpled and deformed. Hundreds of layers are being animated in each of the seventeen shots, on top of low-altitude graphics taken by actually sending up cameras in weather balloons 23 miles up.
In total, it took the team of animators and CGI specialists more than a year to create the single 2 minutes 30 sequence.