NOLAN: The tesseract towards the end of the film...
...was one of the most complicated things to design for the film.
It was the thing we started with, Nathan and myself...
...and it was the very last thing that we actually pinned down.
Even though it was a considerable set that needed to be built, that took a long time.
The complexity of it is something that I don't think the audience will be able to grasp...
...while they're watching the film, because it's based on the concept...
...of suppressing a spatial dimension and substituting time...
...for one of the spatial dimensions...
...creating an array that can display time as a spatial dimension.
But my feeling was very strongly that, if we knew what the rule set was...
...and how it would work mathematically, and if we were true to that in building the set...
...and then in conceiving how the visual effects will expand the set...
...that the audience would feel a logic behind it.
A tesseract is the three-dimensional shadow...
...of a four-dimensional hypercube that's been unfolded.
So if you imagine-- You know, when you take a cube, let's say a die...
...and if you unfolded it out, you'd end up with six panels...
...in a roughly crucifix shape.
Well, a tesseract is the same thing, but instead of flat panels...
...each of those faces of the tesseract is a three-dimensional cube.
When Cooper enters the tesseract, he finds that it really just shows him...
...one place in space, which is Murph's bedroom.
But it shows it at multiple points in time.
We came up with this idea that all the objects in the room, and the room itself...
...would be leaving these traces in space time, these world lines.
Cooper cannot go-- Physically go back in time.
He's outside of space and time when he's inside the tesseract.
But what he can do is he can send a message into normal space time.
And he can physically move these world lines, or the extrusions, as we call them.
And that sends a wave traveling along these things...
...and that enters the room and affects the objects that are inside the room.
And this made perfect sense because, again, according to Einstein...
...that's what gravity is. Gravity is a wave that propagates through space time.
You always have one set, particularly on this film...
...where it's like, "I don't know how to do that.
Let's just ignore it for a while. As long as possible."
NOLAN: There are a lot of different techniques that went into trying to visualize the tesseract...
...and the geometry of it.
The first thing that I asked Nathan to do was to build an infinity box...
...and that's really a set of cubes with half-silvered mirrors.
It was actually the first thing we tried on the film at all...
...was to visualize the tesseract in terms of infinite geometries.
CROWLEY: It was the first model that we can bounce off.
So we built this thing, and the rooms went on forever in all directions.
It wasn't right, but it was a perfect place of trying to describe to everyone...
...coming onto the film the surrealness of what we wanted to achieve.
We had that model for months, and we never touched it again...
...because it was like, "I don't know where to go from here.
This is really difficult."
NOLAN: And that gave us a starting off point, but it was many, many months...
...of experimentation in other directions before we came back to that...
...as being something that was important to the overall design.
In the meantime, we did a lot of different model making.
We had our model makers building what we called "extrusions of things."
Stretching objects in different axes.
Viewing them in different ways through the prism of a different dimensional viewpoint.
Myself, Chris and Paul Franklin suddenly had one of those moments where...
...you turn something upside down. It's like, "Oh, yeah, there you go."
Which moved the design forward, and then that allowed us to actually draw it.
NOLAN: Paul Franklin had a team doing all kinds of, just, sort of, blue-sky research...
...into different ways of representing time as a spatial dimension.
We did a lot of explorations in that regard...
...before we arrived at the final rule set...
...which was really very late in the day.
It was really just at the point where it would be possible to build something...
...that we could shoot in.
CROWLEY: Yeah, that's why it was intense, is because it was challenging design-wise...
...and then practically it was challenging.
Getting everyone used to the fact that we're gonna build some stretch furniture...
...and the room we're gonna stretch in X, Y, Z axis.
And we built, I think, 80 or 100 by 60.
But it was a big old set.
FRANKLIN: But then there was a long, arduous process of recording the shapes...
...of every single object in the room...
...and reproducing it digitally.
And then from those shapes, generating these extruded shapes...
...which would connect the versions of the rooms together.
And then what we had to do is we had to export that out...
...as stuff that Nathan's Art Department could actually build physically.
CROWLEY: We were thinking we could just paint them. We ended up printing those spectrums...
...and wrapping them. An enormous set of elements that stretch.
If you have light coming through a window on one plane...
...you know, you have the landscape from the inside, and then on this side...
...you have a room that's lit. But how do you light that room...
...because you're looking through the glass.
The tesseract represents something that is extremely tactile, tangible...
...and extremely real.
And for me, also the lighting approach was very much motivated by that same thought.
As this room is reproduced endlessly in that space...
...we also have the same windows reproduced endlessly in the space.
And I just really did my best to make this feel real in that way...
...to make the light directions, and the light spill, and the ambient light--
To make it feel as if it was all coming from those windows.
Every single interior surface had a projection running on it.
So in the last few weeks...
...I think we had something like maybe 15 projectors running simultaneously.
And there were some scenes which are just entirely lit by the projectors.
We were using the projectors as a light source.
So the tesseract for me...
...was probably the three longest weeks of my stunt career.
Chris, he's like, "I'll be honest, I'm not really sure...
...where he's gonna go at the moment, because we're still working it out."
He's like, "But be prepared to fly him anywhere within this box."
It was a lot of wire work.
It was a lot of time hanging in a harness.
Matthew spent hours in that harness.
His stunt double would rehearse everything.
We'd have it all dialed in, we'd bring Matthew over...
...we'd show him the action and what he'd have to do...
...and he'd be like, "Okay, put me up."
So we'd put him on, take him up, and he'd replicate it...
...again and again when they needed it. And it worked really well.
NOLAN: Matthew certainly found that set to be extremely helpful to his performance...
...because he could understand, finally...
...what, in the script, had been extremely abstract as a concept.
He was suddenly able to actually see how he could interact with that environment.
It became quite important.
McCONAUGHEY: Christopher and his brother, he wrote completely new rules...
...for fourth dimensions, fifth dimensions, space time.
And then, you know, following through on those rules in our final third act...
...of this world that he's created, that is incredibly abstract.
I mean, in the center of it, though, the heartbeat, is a father...
...faced with the fact that his daughter, who's 30 years older than when he left her...
...thinks that he abandoned her.
Love is space time. Love is that fifth dimension.
Love is that thing that travels through time, forward, backwards, up and down.
You're dealing with the most weighty scientific theories...
...and the most abstract, sort of, science, basically, but you're carried through it by...
...the amazing love that there is between Cooper and his daughter.
What we've tried to do is balance emotional clarity...
...with the challenging nature of the geometry of the sequence.
And for me, refining the sequence was all about the emotional side.
And then as we came to actually execute it...
...that's where the mathematical design of these concepts...
...and how we were gonna portray this rather fantastic geometry...
...that became the whole focus of that prolonged process.