The behind-the-scenes story of Alice in Borderland — THETA Z1 360 degree camera used for CG production!

The show opens with an impressive scene at Shibuya scramble crossing. The main character Arisu and friends are pursued into the station leaving behind the crowded Shibuya crossing. Moments later they emerge to find the people have vanished and the streets of Shibuya have been completely abandoned. On top of that, the entire sequence was shot in a single, uninterrupted cut, an impressive feat leading to much talk in the media.

Alice in Borderland Only On Netflix
© Haro Aso, Shogakukan / ROBOT

In reality, the scene at Shibuya crossing is almost entirely CG. The only real things in the shot are the main characters, the people on the street, and small parts of the set such as the street poles, the ticket gates, and the public toilet into which the main characters make their escape.

© Haro Aso, Shogakukan / ROBOT

THETA Z1 was used for High Dynamic Range Imaging (or ‘HDRI’) which was necessary to create a realistic CG world with natural lighting that is indistinguishable from the real thing.

We asked Atsushi Doi, VFX supervisor for Alice in Borderland, about the secret story behind the production and how the team utilized THETA Z1.

CG production of Alice in Borderland

Alice in Borderland draws us into its thrilling world of escalating survival games in which the stakes are life and death. But right in the beginning the stage is set by the impressive scene in which the always-crowded Shibuya crossing becomes eerily empty in an instant. How was this scene shot?

The scene was shot at a large outdoor open set in Ashikaga, Tochigi. Everything except for the performers and some set pieces such as the ticket gates and toilets are computer generated.

Wow, it is so surprising that the background of this scene is almost entirely CG!

The famous scene, in which the main characters run into a toilet at the station only to emerge shortly after to a city devoid of people, was done in one continuous shot, which would have been impossible in the actual location.

What was the most difficult aspect of this CG production?

Most of the CG productions that I’ve been involved in were fictitious towns and imaginary creatures, but for Alice in Borderland, we had to create a virtual Shibuya crossing, which many people know, and that was the most challenging part.

On top of that, there are a lot of people in some parts of the scene, and less in others. Less people means less information, which means a more obvious difference between CG and live action. So, the issue was how to recreate reality in detail.

How was THETA Z1 used in this CG production?

The image data taken with THETA Z1 was used for CG lighting by creating light source information called HDRI.

Image edited from RAW taken with THETA Z1

By using the actual light source information from HDRI for CG lighting, it is possible to create a more realistic CG scene that fits the live-action part seamlessly.

Reference JPEG image taken with THETA Z1

*HDRI: An image format that can express brightness in a range close to that of the real world, from the appearance of high-intensity light to the fine shadows in dark areas. Since the brightness is expressed by a 32-bit floating point value for each RGB pixel, the dynamic range is much wider than the conventional 8-bit integer value. When it’s used for color information in CG lighting, it is possible to create CGI that looks less strange or out of place even when combined with live-action.

How does the HDRI process work?

The RAW data from THETA Z1 is shot by bracketing the exposure by using different shutter speeds and is then combined into a single 32-bit image in software such as RawTherapee or PTGui.

With 32 bits, it is possible to acquire a wider range of color information, and because of that, it’s also possible to acquire light source information that is closer to live action.

Multi-bracket data taken with THETA Z1

I took bracketed photographs with THETA Z1 in the morning, afternoon, and evening at the set in Ashikaga. The light source information of the image data taken with Z1 was then used for CG lighting of the virtual Shibuya crossing scene.

Did you also use THETA Z1 for any other scenes besides the one in Shibuya crossing?

I also used HDRI data from Z1 in the scene where the main characters are chased by the black leopard in the tunnel, which appears in episode 4.

Image edited from RAW taken with THETA Z1

Oh, that scene was also very powerful! The leopard is fully CG, right?

Yeah, in the tunnel scene a fully CG black leopard moves around and on top of the car.

So, I used the Z1 to take multi-bracket shots in the actual tunnel, according to the leopard’s position on the car and in front of the car door as it stalks around the car.

Reference JPEG image taken with THETA Z1

The HDRI light source information is used for CG lighting of the black leopard.

Black leopard with HDRI lighting taken with THETA Z1

© Haro Aso, Shogakukan / ROBOT

About THETA

I’ve heard you have been using THETA since the first model released in 2013. What made you start using it?

Since it is a compact camera that can easily shoot 360 degrees, I thought maybe I could use it for location scouting and purchased the first model. After that I wondered if this could be useful for HDRI and CG applications. I also tried shooting at different shutter speeds.

THETA S was released after that, and I purchased it because it was better and allowed more shutter speed settings. It was around that time that I got to use THETA for work with HDRI even in serious CG work. I used THETA S with light source information to create a part of the CG in the movie Death Note.

How did you use HDRI differently between THETA S and a normal DSLR?

THETA S couldn’t shoot raw and was not suitable for realistic CG. So, I used a DSLR camera to shoot HDRI when making realistic CG, and used THETA S for scenes that didn’t need that much realism.

What do you think is the advantage of THETA in HDRI shooting compared to DSLR cameras?

With a DSLR camera, it’s necessary to take multi-bracket shots in 6 directions, right, left, front, back, up, and down, and then connect those images to create a 360 degree HDRI.

On the other hand, THETA can shoot in all directions with one shot, and there is no need for stitching to create 360 degree images. It makes the whole process much more efficient, so THETA S made shooting HDRI very convenient.

You mentioned that you used the flagship model THETA Z1 with HDRI for the first time in Alice in Borderland. What has changed from THETA S to Z1?

Z1 has been improved significantly in terms of image quality and it can shoot raw images and has 3 aperture settings, allowing for more control.

I compared the HDRI of Z1 with that of a DSLR, and I feel there is not much difference between them.

It may be better to use HDRI from a DSLR to generate realistic CG with detailed depictions of objects such as cars, but I thought Z1 would be sufficient enough for normal scenes.

Are there many people in the CG industry who use THETA for HDRI photography?

Since THETA Z1 supports raw, I think that the number of professionals using it has increased. But still, I’d say most people are shooting HDRI using conventional DSLR cameras.

By using DSLR cameras to shoot HDRI, the resolution will be higher but it will take time and effort to generate the 360 degree images. The beauty of using THETA is not only to shorten the shooting time, but also to make the image processing work considerably more efficient.

Recently, there are many individuals who produce CG. And I think those people can create more realistic CG easily with a device such as THETA that can easily shoot HDRI.

Future Vision

What would you like to challenge in the future?

I want to simplify the process of generating such CG images without sacrificing quality. When looking at overseas works, I’m often surprised with the amount of CG that is used. It is much more common than in Japanese productions. It seems more and more productions use digital sets where pretty much everything other than the cast is all CG.

Season 2 of Alice in Borderland has been announced.

The production will likely feature more scenes that heavily rely on CG in order to express the story in it’s full potential. That means season 2 of Alice in Borderland will be the next big challenge for me.

Thank you very much! We look forward to your next project with THETA Z1!

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Profile of Atsushi Doi：

Director and VFX Supervisor of Digital Frontier Co., Ltd.,

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Alice in Borderland Only On Netflix
© Haro Aso, Shogakukan / ROBOT

Synopsis:
Arisu—a listless, jobless and video-game-obsessed young man—suddenly finds himself in a strange, emptied-out version of Tokyo in which he and his friends must compete in dangerous games in order to survive. In this strange world, Arisu meets Usagi, a young woman who’s navigating the games alone. Together, they set out to unravel one mystery after another as they risk their lives and confront what it means to live.

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Series Information
Title: Alice in Borderland
Format: 8 episodes
Based on: The original graphic novel “Imawa no Kuni no Alice”
by Haro Aso published by Shogakukan Inc.
Director: Shinsuke Sato
Cast: Kento Yamazaki & Tao Tsuchiya

Netflix official HP：Alice in borderland