Here’s what went into the visual effects of ‘Shang-Chi’s’ crazy bus sequence: Part 1

·September 17, 2021
·Ian Failes

The film’s VFX supervisor Chris Townsend breaks it down.

Early on in Destin Daniel Cretton’s Shang-Chi and the Legend of the Ten Rings, best friends Shang-Chi and Katy are on a San Francisco Muni bus when they are attacked by the Ten Rings. Shang-Chi surprises Katy by fighting back—big time.

The on-bus fight, which takes place while the bus is out of control, came together with a mix of location and reference shooting in San Francisco, and heavily choreographed stunts filmed on a bluescreen stage with buses and vehicles on motion bases in Sydney.

In Part 1 of befores & afters’ coverage of the bus shots (part of our larger Shang-Chi coverage), we talk to VFX supervisor Chris Townsend about orchestrating the sequence. Part 2 will dive into the final VFX work by Luma.

Preparing for a bus fight

Chris Townsend (visual effects supervisor): The bus fight sequence certainly is one of the major set pieces in the film and was really fun to work on. Joe Farrell, our second unit/additional VFX supervisor, took the lead in the day-to-day work with Luma, the VFX company that did the final shots.

Planning the sequence was quite complex, as we had to map out the route that the bus took through the streets of San Francisco, always trying to maintain a downhill motion during the most dramatic parts of the fight. Obviously San Francisco isn’t really quite that big so we had to get creative, but tried to maintain some geographical logic.

VFX supervisor Chris Townsend (right).

Joe and I spent a long time mapping out the entire route and once created, we asked the small additional unit who was filming in San Francisco to shoot array plates along that path. There were production restrictions with some of the streets we wanted to shoot so we had to improvise. However, we managed to get most of what we needed in an eight camera array set of plates, mounted on a car, driving through the streets. These array plates were then fastidiously stitched together to create the world of San Francisco outside the bus.

Planning the shoot

The shots of the fight outside the bus relied more on full CG builds of sections of the city, which Luma did based on LiDAR and texture photography taken on location. The entire flight sequence was very carefully prevised (by The Third Floor) and stuntvis’d first so that when we got to the actual shooting we knew exactly what it was we were aiming for; it was an interesting process iterating between stuntvis and previs, often starting with previs, taking that into the stunt world, having them do versions based on the general idea in the previs, throwing in some more ideas and suggestions, taking it back into the world of previs to change camera angles etc.

Simu Liu as Xu Shang-Chi / Shaun during shooting of the bus fight.

It worked very well as a methodology and I think the sequence as a whole benefited hugely from us making a plan and sticking to that plan. It was a very complex sequence to shoot made even more difficult as it was in such a confined space, swinging around on a gimbal.

Bus breakdown

We had two different complete articulated buses, without wheels for our bluescreen photography; one was on an air bladder system, for general driving shots, the other on a six axis gimbal for the more dramatic twists, turns and jumps. For the exterior shots, some were shot on the bluescreen stage, and we tried to use the complete bus, as photographed. However, for several shots we wanted to twist the back half of the bus more than it could physically do, or bend it more; this required replacing the back half and the articulated joint in CG.

The bus and garbage truck at the Sydney shoot.

Similarly, for the practical shots of the bus driving in San Francisco, sometimes we could use the actual bus, just having to add digital double passengers inside, but other times we had to add or replace the back half. We had several buses we used there, some set up for driving generally, some where the back half was removed and the engine moved to the front of the bus (the engines on these articulated buses are actually at the back), some rigged for the big crash at the end. They all needed to be augmented to some degree.

In terms of getting the physics right, Destin, the director, always wanted to have the drama amped up a bit, with the bus careening and lurching downhill; this meant we had to tread that fine line between reality and movie reality. We studied footage of crazy bus stunts and real bus driving plates to get a better sense of what a bus can do… yes, you can drive a bus on two wheels! But ultimately it came down to what served the story and felt right, trying never to break the sense that this was a real bus doing these things.