This is where Matthew McConaughey’s Cooper encounters the Tesseract: an artificial construct that allows him to perceive time as a physical dimension.
The design and execution was a total collaboration between Nolan, theoretical physicist and exec producer Kip Thorne, the art department led by production designer Nathan Crowley, and VFX studio Double Negative led by co-owner/supervisor Paul Franklin. "We looked at works from Gerhard Richter, who has this technique of scraping the paint across the canvas and leaving these trails, so there’s this sense of a historical record," Franklin explains. "The other thing I looked at was slit scan photography, and of, course, the Stargate in ‘2001,’ but it goes back a lot further than that.
"Slit scan is this process that records one specific location across a whole range of moments. You have a slit and an aperture and you move the negative behind it so the neg is recording everything in a continuous stride as it slides past. For me, what was interesting is that you’re turning time into a horizontal axis of the photograph as a record of the time of the exposure," Franklin says.
"So I thought that might give us some sort of lead in to how we would represent the concept of these world lines. A world line is something that comes out of Einstein’s theory of relativity: It’s the idea that every object, every person, and every piece of matter in the universe is leaving a trail in space-time behind it because we live in a four-dimensional universe. We have three physical dimensions and one dimension of time, which is always moving forward. And we had this idea that the Tesseract was a concept that shows time as a physical dimension, so Cooper could interact with it and move back and forth across the timeline and find specific moments in the history of his daughter’s bedroom."
And the world lines were the obvious way to create this timeline: each object and all the people in the room extrude these timelines in all three axes, and the tricky thing was representing it in such a way that it wasn’t too complicated and hard to follow or that it didn’t obscure what was in the rooms.
"And Chris thought that was fascinating," Franklin adds. "We gave the geometry to the art department to physically build the Tesseract — cut them out and then extrude them in physical space. And then we rendered what the surface of these tubes should look like and we turned those into very high-res laser prints and they pasted the computer-generated imagery physically onto the set to create all the textured colors on the world lines.
"We used projectors on set and projected animated images and at one time had 18 projectors working. We then enhanced that with animation streaming along the timelines. And then all the objects in the rooms are connected to the world lines by these very, very thin, diaphanous threads, which are essentially solid extrusions that we’ve culled out along the geometry. We had to body track all the actors in the room as well and and then generate threads off them, and also sample the photography so it picks up the correct curve."