VFX Supervisor Stephen James and Virtual Production Supervisor Daniel Paulsson, both of DNEG, tell us how they used a combination of LED walls on set and CG in post to recreate scenes from Tokyo and the Japanese countryside
Directed by David Leitch and starring Brad Pitt, Bullet Train sees five assassins with separate but related missions battle it out on a high speed train as it traverses Japan.
All of the window views are CG. LED walls were used for low-light and night scenes, with countless shots being captured as final in camera.
Led by DNEG VFX Supervisor Stephen James, VFX Executive Producer David Fox and VFX Producer Saado Aboukhazaal, DNEG delivered over 1015 shots for the film.
Here Stephen James and Daniel Paulsson explain why LED walls were a good fit for this project, how they created the environments, and how they switched between LED wall and greenscreen to suit the situation.
Please tell us about your process for creating the environments for this film.
Stephen James: The initial direction was that each environment and station needed to feel very unique – whether in the architecture, natural environment, or in the lighting. Because we had to pass through most of Japan, we needed a lot of variety so we started with extensive reference gathering.
As Covid precautions were still in effect, traveling to Japan and filming the environments or even sending out a shoot team to gather reference wasn’t an option. To get around this, DNEG worked remotely with JAID Productions, a photography team located in Japan. Our shoot supervisor Dan Kunz trained this team remotely. The local team captured photography and data everywhere, from the streets of Akihabara at night to the rice fields of Maibara at sunrise, using shoot kits we had sent and trained them on. Working with them was one of the positives that came out of these restrictions.
Once the data and photography was collected, we were able to generate a variety of assets, environments and dress each of them to make them unique. Our environment team utilized new techniques using OpenStreetMap (OSM) data from throughout Japan. This gave us a blueprint we could procedurally fill with our vegetation, various building styles, streets and props. We then had a team of environment artists add in much more detail and style, as well as train tracks with fences and overhead rail structures to give the repetition and sense of speed you get when travelling at 300km/h.
Have you worked with LED walls before, or was it new ground for you and your team?
Daniel Paulsson: While DNEG has worked with large scale LED walls on other projects such as ‘First Man’, ‘Devotion’ and ‘Foundation’, this was the first project for me. Luckily we had supervisors and other members on the team that had worked on the previously mentioned shows to help answer any questions when they arose.
Did using LED walls and virtual production techniques require your team to take on any new roles or responsibilities they weren’t used to?
Daniel Paulsson: Since the content on the walls was pre-rendered for this project, the team roles were close to the same as a normal VFX delivery. But, as part of the project was pre-rendered in Unreal Engine, we did end up with additional people, from our Virtual Production Department, on the team that would not normally be present in post.
Why were LED walls a good fit for this project?
Daniel Paulsson: The production design lent itself to using LED walls, as the set contained a lot of reflective materials such as mirrors, glass, chrome and shiny plastics. If a traditional greenscreen approach would have been used, the images would have been filled with reflective spill that would have been hard to remove and replace in post production. That coupled with the fact that the view through the windows were limited, as the windows on a bullet train are quite small, made the LED walls a perfect match for this project.
Please tell us about the LED wall setup you had for the shoot – were there any practical challenges during filming?
Daniel Paulsson: The Volume consisted of two large 30.5m long and 5m tall LED walls on each side of the trains, with two smaller 2.5m by 5m walls in each end of the train, making it a total of six screens. While there were gaps in the walls at the ends, for stage access and to let us move trains and screens independently of each other, those gaps were out of sight of the camera. The DNEG content was delivered to the screens though a Disguise playback system provided and operated by Lux Machina in conjunction with the Client VFX Supervisor Mike Brazelton.
Are there any particular challenges around using LED walls to create window views?
Daniel Paulsson: The main challenge for using LED walls for window views is physical space. The further away from the windows you can place the screens, the more accurately you’ll be able to optically replicate what would happen if it was filmed on location. But if further away, bigger screens and more stage space will be needed.
Did your window views require much work in post?
Stephen James: Any time something wasn’t working on set, they would switch to green screen/bluescreen on the LED screens knowing that we could adjust in post. There were only a few cases where this was required but it was great that this was an easy adjustment to make on set.
Once the sun rises, we switch to full CG environments in post. We drew the line there as we knew the LED screens would work well for night and lower illumination environments, and that we could achieve better results in post for anything brighter sequences. After sunrise is also when the action is amped up and we would be adding much more FX.
What are the advantages of using LED walls and other virtual production techniques over alternative methods? Were any of those advantages particularly apparent on this project?
Daniel Paulsson: Using LED walls, instead of a traditional blue or greenscreen setups, not only means that you don’t have to replace your greenscreen in post, the actors and sets will also have a more accurate lighting as they are also lit by the LED walls. For those sequences where you still want to use a greenscreen, there is the option to turn the whole or parts of the LED screen green and use that as an almost perfect greenscreen. For this project, having already pre-established footage outside the windows meant countless shots that traditionally would have been tasked to VFX to replace green screens, where all captured as final in camera.