Production VFX Supervisor David Sewell talks about re-creating WWII Europe for this dramatisation of the early days of the SAS – environments, explosions, water FX and paratroopers.
Dakota transport aircraft
BBC One TV series SAS: Rogue Heroes is a historical dramatisation of the formation of the Special Air Service (SAS) during World War II. The series is based on the book of the same name by Ben Macintyre.
The visual effects for the show is the work of Ingenuity Studios, both for Season 1 that aired in 2022, and now Season 2 that has just reached viewers starting in January 2025.
Digital Media World talked with Production VFX Supervisor David Sewell about Ingenuity Studios’ work on the second season of the show. “The environments in Season 1 had been desert and sand, and much of our work focussed on aircraft explosions,” he said. “But Season 2 is located in Europe, and because we have so many shots take place at or near the sea, water effects were a priority. It was the same time period, but quite a different environment.”
David was on set throughout the shoot, and started on supervision about four months before principle photography got underway. Most of the filming took place in Croatia, with further sequences shot in Sicily, Slovenia and Italy, and in the UK for certain specific locations.
Dakootas in Flight, D-Day
Scale and Impact
“Because we started working with the production so early on, they were prepared to let some of the decisions we made at that time influence the script development. For example, the opening scenes in Episode 1 were to feature a massive armada comprising thousands of ships and landing craft, all headed for the beaches in preparation for a big invasion. It was an ambitious vision and at that stage, the production wanted to know if we should ask the writer Steven Knight to scale it back, to ensure it was feasible.”
In the end they did successfully bring that scale and impact to the screen for those sequences. But David feels a lot of benefit can be gained in working together in this way before the script is finalised, to understand how far you can push the use of effects to achieve what you want, while saving time and budget.
Across the series, historical authenticity and realism were high priorities for the production. Ingenuity researched the period with the production’s Art Department, who sourced blueprints of the vehicles, boats, tanks and aircraft. The production built, at some expense, a practical marine-safe landing craft for the shoot. Ingenuity then built CG copies to match it.
“That was a key approach to realism on this show – from assets like the vehicles to effects such as water simulations and explosions,” said David. “The goal was to include real elements in-camera as far as possible, and then use digital artistry to replicate and extend that same look to build the world of the story. It helps the audience achieve that suspension of disbelief and helps the artists with lights, textures and detail.
Panzer 4 kit model
“In Episode 4, the tanks we created were intended to be the Panzer 4, a very large ‘super tank’. As this model was less common than others, we couldn’t find a real one, but the production managed to find a kit model of one to use on set. It needed some digital enhancement but in the end, what you see on screen is a fully accurate, historical Panzer 4.”
Airborne
Aircraft were handled similarly to the tanks and other vehicles. The Dakotas, the transport planes, are not too hard to source. “We had one practical example on set and build digital replicas to fill out the scene. We also had one of the dive bombing fighter planes, a Stuka, to work with, which you’ll see attacking a dining table set up outdoors for breakfast,” David said.
The gliders were interesting, and a bit more challenging. These aircraft were sent out from a fleet of ships off shore, intended to land and clear the way for the main attack – although in reality the operation had limited success. The gliders had a very lightweight construction of wood covered in canvas, with a rounded front that can open up and be used to carry jeeps.
The result was a very useful aircraft but with a design that doesn’t look very aerodynamic. “As we built, rigged and animated them, we also had to remember that centre of gravity is critical for any airplane. Without an engine to weigh them down at the front, their design and motion are different to a standard powered plane,” David noted
Locating the Action
Beyond assets, authenticity of the environment and geography were important to achieve across the episodes. The shoot locations in Croatia often had the right look, but the team needed to place the sea into the right position the backgrounds and add landmark buildings. Viewers might not know exactly what to look for, or recognise every detail, but the collective result is important to the success of the project.
The backgrounds were a combination of digital matte paintings and 3D elements. The Italian coastal town of Termoli, the site of a pivotal battle, was filmed at Buje in Croatia, an inland city. David said, “The location was carefully dressed for the shoot but still needed adjustment in post. We looked at photo reference, re-graded the colour of the walls, re-built key buildings – on top of the clean-up effort to clear away the signs of modern life, from signage and traffic lights to air-conditioners and satellite dishes.
“Our best assurance of the success of our environments came when members of the SAS themselves watched the series and approved the looks and authenticity.”
Into the Water
Realistic water simulations remain a major challenge for FX artists. David explained that any opportunity to include real water in shots that need simulations is going to be an advantage. “Our producer Stephen Smallwood is very enthusiastic about VFX – he was good to work with and keen to take advantage of any techniques we had that would help us save time and trim costs. Water was one of these.
“While we advised him against shooting scenes with the boats on land and trying to create an entirely CG water environment, we explained that the best compromise would be to shoot the sequences with a boat in a water tank, as large as possible, and then extend both the water and the boats digitally.
“That way, we could control everything, have real water surfaces in-shot and preserve the water interactions as reference. Although hiring Leavesden Studio’s water tank was a fairly costly option, it gave us the best look. Our simulations match into those characteristics captured in the plate and made an ideal environment to composite our boats into.”
Jailbreak
A prison escape sequence was an example of not only blending digital work into a real setting, but of also combining imagery from three different locations, and performances from two different actors – a stunt performer and the principle actor. Main character Lieutenant David Stirling attempts to escape by scaling the exterior wall of Gavi prison, a fortress in Sicily that had been repurposed during the war as a prison camp for Allied officers. “The talent wasn’t available to travel to the shoot location in Croatia, and in any case, asking him to scale a stone wall above a 60ft drop was never an option,” said David.
“For the wider shots, we organised a drone at the story’s setting, Gavi fortress. From these shots we lined up camera angles for recording the performances. For the mid-range shots using a stunt actor above a 40ft drop, we could add 2D face replacements. For close-ups of the hero, we had the main actor performing above a 10ft drop at a UK studio. Both of these were extended downward in post to create the full 60ft drop.”
Lighting across the three locations was anticipated as a critical issue, as was the texture of the stone wall. Each shoot meant finding the right time of day, and although the close-ups were meant to employ a cast of the real stone wall at Gavi for textures, the match wasn’t ideal. The team wound up with three different brick patterns, which they graded to help minimise distraction from the drama of the sequence.
Tracer Fire
Authenticity extended to depicting the tracer fire from the soldiers guns at night. The basis of tracer fire is that every sixth bullet is built with a small pyrotechnic charge in its base. When fired, the charge is ignited and makes the bullet’s trajectory visible to gunmen at night so they can see where they are firing. David said, “Simply showing every sixth bullet sounds like a simple task, but making it look convincing, consistently, involves controlling several physical forces at once.
“First, the bullet wiggles as it is released, creating motion blur. The artists also have to keep track of the rate of firing, gravity as each bullet flies into the distance, and the ricochet as it strikes. To get all of these to interact consistently each time. We built a custom tool to run in Nuke, starting with a base version of a simulation. We tried first with a regular 3D application like Houdini or Maya but had more success with Nuke compositing software, using its integrated 3D environment.
“This technique gave us the foundation of the effect but then almost every shot had to be tweaked to adjust the glow and speed and so on. Throughout, as always, checking our work against our reference material of real tracer fire was essential.”
Tragedy
One of the show’s most emotional scenes comes when a 10-year-old Sicilian boy is severely injured and dies during a German attack. The child resembles a family member of Reg Seekings, a soldier who stayed behind in Sicily. He befriends the boy's family, and when the shelling suddenly starts, Reg orders the family indoors. Nevertheless, the family are hit. Reg tries to help the little boy but finds him barely alive with a deep blow to his intestines. Ultimately, Reg has to kill him.
Makeup and prosthetics to the level required here are not allowed with child actors. When Ingenuity’s team approached the sequence, extreme subtlety was needed – showing the boy's injuries were dire enough to warrant Reg’s action, without depicting them in an overly horrific way. “We worked on a very fine line. We found that slightly animating the intestine as well as creating the asset realistically using medical reference, gave the sequence a much more immediate, lifelike feeling. Recognising the right level of realism was the trick, and knowing when to stop. It was a good example of not letting VFX take over from our real focus of attention.”
Art of Explosions
A similar kind of decision-making was needed for explosions. When a shell lands in front of a truck, officer Paddy Mayne is only about 3m away. The team questioned whether or not this would have killed him. Military advisers said that due to the position of the truck it would have just missed him. This meant placing the explosion in the shot to make sure he was visibly shielded, and make that the story they were telling.
About half of the explosions were based on practical explosions on set. Starting with these in the plate, they added further fire and flames and flying debris. But sometimes they needed to start completely from scratch, combining simulations and 2D elements to build up the right look, though David said he still prefers to have something there, in-camera, to base an explosion on.
A technique he especially likes because it can work in shots that include a camera move, is mapping 2D elements onto a 3D object. He said, “It gives you extra realism and more control over the result as the camera moves around the explosion or across the environment. This was our method when we see Reg running toward a tower to stop a sniper, while an explosion goes off right next to him.”
Destruction and Materials
Creating a train tunnel explosion, caused by the Panzer tank firing, employed a small SFX cork debris explosion on set. This maintained safety but gave the artists some interactive lighting in the plate to work with, and gave the actors something to react to. “From there, we simulated a far bigger explosion with large rocks and stones flying away, landing near the actors,” said David. “Complexity came from incorporating the physics of angled constraints involved in tunnel and bridge construction and collapse, and from showing how the smoke rolls around the curved ceiling and how the rocks bounce off the walls internally.
“We spent a fair bit of time prepping the models and materials to react correctly to our simulations. In a similar way to our train tunnel explosions and collapses, we built the bridge over the railway with individual bricks and foliage to accurately match the real bridge, rather than create a complete, new CG bridge. That way, we could use the original photography and lighting. We found lots of references of similar bridges collapsing from detonation and ran multiple sims until we were happy with the match. If you look carefully you can see the foliage accurately reacting to the bricks and explosion.
When a bazooka hits a tank, the resulting explosion had to be carefully considered. From found references we noticed tanks are targeted under the turret as the weak spot and quite often the whole turret comes off – sometimes flying 20ft into the air! – which called for modelling the internals of the tank. In the final simulations, you’ll see the tanks engulfed in smoke and firing very quickly, all matching our reference.”
Paratroopers
Near the end of the last episode of this season, 60 American Dakota planes are seen in the sky, heading towards northern France and dropping paratroopers ahead of D Day. Ingenuity was able to refer to real footage of many of these planes and parachutes by watching the 1977 film ‘A Bridge Too Far’. CG Dakota planes, parachutes and the environments of France below them were all created digitally.
David said, “The parachute drops of the troops involved a carefully modelled parachute to match the genuine silk parachutes used on set. Our chutes also had to be digitally rigged so that they could be used in an authentic cloth simulation.
“The final shot of the show sees our hero Paddy Mayne falling backwards out of the plane as part of the D-day invasion. This shot was simulated multiple times to choreograph it to the director’s vision – a camera move that sees Paddy’s chute lead the way and open first followed by multiple chutes opening behind, all neatly framed by the text on screen. Orchestrating it all together was a challenge. We also created a parachuting jeep held up by five chutes, as they also did back in the day, obviously needing quite different dynamics. www.ingenuitystudios.com
Words: Adriene Hurst, Editor
