“We didn't use an actual cardboard box. We made one out of poles.”
Kojima described a constraint of the motion‑capture stage: the cameras read reflective markers, so props cannot be opaque and a wall is built only as a frame because it has to be see‑through for the cameras. He gave a recent example: they shot a scene with a cardboard box but did not use a real box, they made one out of poles, and the actor had to handle the skeleton as if it were a solid cube, without putting fingers where there would be cardboard. He also confirmed they are filming the making‑of and will share it at some point.
“there are all these cameras that are capturing data from the reflective markers. So if we wanted to create a wall, we can't cover it up completely since the cameras can't capture the other side of the wall. We need to create just the frame of it. For example, we shot a scene with a cardboard box the other day. […] Yes, because it needs to be see-through for the cameras. […] We're filming it. […] We'll share it eventually.”