Apostle Interview: Christian Lett – Visual Effects Supervisor – Bait Studio

Apostle Interview: Christian Lett – Visual Effects Supervisor – Bait Studio

December 20, 2018 – Excellent Interview by Bait Studio. Interview by Christian Lett, Visual Effects Supervisor. Today, they talks to us today about his work on ‘Apostle’.

Apostle is a 2018 British-American period horror film written and directed by Gareth Evans and starring Dan Stevens, Lucy Boynton, Mark Lewis Jones, Bill Milner, Kristine Froseth and Michael Sheen. It had its world premiere at Fantastic Fest in September 2018. The film began streaming on Netflix on October 12, 2018. It has received positive reviews from critics for its visuals, cinematography, performances, and unique blend of horror genres.

// From Christian Lett, Visual Effects Supervisor, Bait Studio

Can you tell me about how you became involved with Apostle?

We got involved just as filming began – producer Ed Talfan invited us to meet with Gareth and discuss a number of VFX shots that required on-set supervision. At that point we weren’t necessarily in consideration to do the work, as Gareth was planning on using Clay Studio in Indonesia for all the VFX work (they had provided the VFX on both his Raid films).

Let us know about the core team of Bait Studio who worked on ‘Apostle’

We had a small team of just 21 people. I was the VFX Supervisor but I also composited a number of shots; Llyr Williams was the CG Art Director in charge of the look development of the CG sequences; Joe Thornley-Heard was our Lead FX TD, supervising Alejandro Echeverry (Fluids TD) and Daniel Wood (FX TD), as well as creating the big cave explosion shot at the end of the film. Santeri Holm was our Lead CG Artist. We had five additional compositors, including Bait’s resident compositor Anthony Williams, and our CG Generalist, Adrian Hanslien, who modelled, textured and made all the fire sims. Peter Rogers was the VFX Producer, with our Production Manager Lucy Lawson-Duckett keeping us all in check!

What are the sequences made by Bait Studio?

We worked on 70 of the more complex shots for Apostle, handling all of the sequences that needed vine and other plant growth, the boat sequence at the start of the film, plus a number of matte paintings and set extensions. We also did the big sequence at the end of the film featuring the cave exploding.

How was the working experience of Director Gareth Evans? What’s his approach for this film?

As a huge fan of his two Raid films I was very excited when I learned I’d be meeting Gareth to discuss the VFX for his next film! I got to work directly with him and his long-time DoP Matt Flannery during filming, and it was always a pleasure to work with them – very down to earth and approachable. Gareth has a very structured approach to VFX, very similar to the way he makes his films – for example he would plan the fight scenes in minute detail with the stunt team and essentially reshoot them shot-for-shot. As the writer/director and editor Gareth had a clear vision of how he wanted the VFX to look, but was open to suggestions about how we tackled things, especially how the vines grew for example. Obviously because this film is set at the turn of the 20th century, any VFX had to look real and organic. He was quite VFX savvy having worked closely with his VFX team on the Raid films, which made it easy to discuss the VFX with him.

How do you balance director’s vision when creating VFX for any movie?

I think that regular communication is key – the earlier we get involved in a show, the longer and hopefully better the relationship is with the director. This makes it easier to discuss ideas and reach compromises. As a filmmaker myself I understand that compromise can be far from ideal, but it’s also a reality since time and money are finite resources; this is especially true on the lower-budget films we tend to work on. Personally I prefer face-to-face discussions, going through concepts and getting to grips early on how the director wants an effect to work within the bounds of the story. If possible we will look for ways to do shots with minimal VFX, perhaps just to enhance a stunt or a practical effect if the budget is tight or the VFX isn’t important to the storytelling of the scene. Our pipeline is organised to produce output at various stages so the director can see the shot progressing, so hopefully there are no surprises when we deliver the shot!

How did you organize the work your VFX Producer?

Once we’d finished shooting, I worked with our in house producer Pete Rogers, and Andi Novianto from Clay Studio to work out which shots best suited which vendor. Gareth was also involved in that process, as he has worked with Clay Studio previously and knew what their strengths were. Pete and I prioritised the sequences we knew would be most difficult, so we could maximise the time we had on the most complex shots. With that in mind we brought in some very experienced FX TDs and got them involved before production began in earnest.

Can you share more about On-set VFX supervision about Apostle?

Of the ten weeks of filming I was on-set for about three weeks, mostly towards the end of filming as this was where the VFX sequences were scheduled. Each day would start with a quick discussion with Gareth and Matt Flannery about the day ahead. I try to get to know as many of the crew as possible because VFX can have an impact on all departments, and you never know when you might need a favour from someone in costume, makeup or lighting! It’s also important to get to know the Script Supervisor, and on Apostle this was no different: Ceri Evans and I would discuss which shots were VFX so she could make sure they were correctly slated. In between filming VFX shots I would do set surveys, take reference photography and prepare for upcoming shots by placing tracking markers. Whenever possible I would use our chrome/grey ball on camera for reference and would take 360-degree HDR panoramas for lighting. I always take my own notes in a Moleskin notebook, recording the lens, resolution, focus distance, etc., which would then be transposed into a spreadsheet for the team to reference during post. I had a great time filming Apostle and was grateful to spend what time I had with the amazing cast and crew, many of whom I’ve kept in touch with since.

Can you explain in detail about the island creation and water simulations?

The vast majority of what you see on screen was real – for example the village was built entirely on location at Margam County Park near Port Talbot. However certain scenes needed matte paintings to change the landscape, in particular the lagoon seen at the start of the film when the boats arrive at the island. This was filmed at the National Diving Centre in Chepstow, which is an old quarry. Gareth wanted a narrow opening to the sea, which would be too small for the steamer to traverse, hence the row boats. Before we shot these scenes I mocked up a rough concept from a still I’d taken on the recce, which served as a starting point for our work, and this got further refined into a final concept by our matte painting artist, and ultimately into the finished matte painting. The camera pans round as the boats pass by, revealing an imposing cliff face on the far side of the lagoon; while there was already a cliff, Gareth felt that it was too lush with trees and ultimately didn’t extend high enough. He also wanted to see the cave opening that features in later scenes and the skeletal tree at the top of the hill that Thomas lays beside as he’s dying at the end of the film, so this required a second matte painting. For the closing scenes, where we’re at the top of the hill looking down at the lagoon, we needed to bring the geography of the lagoon to what was open sea, overlooked from the cliffs at Southerndown. We built stand-in geometry onto which we could project concept art to get the perspective right, before sending onto the matte painter for the final version.

All the water was simulated in Houdini and rendered using Mantra. The stormy sea is actually seen just twice – once through the cockpit window as Frank and Jeremy wrestle with the controls, and once when the Lonely Passenger throws the lamb overboard. Both these shots were filmed in the studio aboard the replica steam boat, which was set on a gimbal. Our fluids TD used the boat geometry to cut a path through the waves and generate splashes. We also generated the surge of water that knocks the crate with the lamb to the floor.

Creating CG Explosion of Blood, Fire and other elements. What is the biggest challenge of this?

This shot was one of the first we started, and one of the last to be completed! Our lead TD had the very difficult challenge of dealing with a cavern exploding, rocks falling, a cascade of blood that was also on fire, which needed to interact with the rocks (and vice versa), with everything falling into the water below. We went through quite a few variations of the rock fall simulation to get something that Gareth was happy with – the complications being that even if he liked the way one particular rock fell, tweaking a force setting even by a tiny amount would change its trajectory and we’d be back at square one!

Can you discuss in more details about the vegetation creation?

We created thousands of vines growing from within the network of branches built into the set, maintaining them for the duration of the shot with them all dying as the shot ends. We needed to build accurate set geometry from which we could grow our vines. Unfortunately we didn’t have the budget for a LIDAR scanner, so we used a combination of photogrammetry and modelling for some of the larger branch structures; the smaller branches were generated using a shell-approximation directly from the plate, which is essentially taking the luminance values and generating displacement in Houdini. This set geo allowed us to procedurally “seed” our vines, acting as attractors for the vines to wrap around, as well as being shadow casters/catchers. The vines themselves were 100% procedural, each having seed points for leaves and flowers. We had fine controls for amongst other things how the vine would search for nearby geometry, and stiffen as it got older. We modelled, textured and animated about 16 different leaves and 4 different flowers, however they would all have slight procedural differences when spawned.

How did you create and animate the FX element?

The leaves and flowers were all animated to have a life-cycle, from a bud, through being fully formed, and finally wilting and dying. Each vine controlled the stage of each of its leaves and flowers based on its own age. The vines themselves were animated procedurally.

Can you discuss in more details about the explosion and the river of blood?

We started by adding a matte painting of the cave, since that didn’t exist naturally within the cliff, and then modelled the geometry that was fractured around the cave opening. This fed into the rock fall simulation, following which we tackled the fluid simulation for the blood. In addition to splashing off the falling rocks and cliff face, the blood needed to “paint” the geo so that it could leave bloody trails behind it. We used the blood as a fuel source for the fire; Gareth was keen that the blood and fire sit on the water’s surface, a bit like oil, and since the large rocks were churning up the water’s surface we had to completely replace it with a separate fluid simulation. Everything was simulated together in Houdini and rendered in Mantra.

Can you discuss in more details about the CG Art Creation of Apostle?

We would often start with concept art that we could show to Gareth and get his thoughts. For the DMPs we would get the Matte Painting Artists to produce their concepts on 8K blowups of the plates, and eventually after various refinements we’d end up with the basis for the final painting. Gareth preferred to see things rendered in context, rather than works-in-progress. For some of the more complex shots that had long render times we had to work with lower-resolution renders, or fewer samples to get the shots through to comp.

Were there any particular shots that empowered you to approach the scene in a new or different way, or explore new ideas?

With the exception of the matte paintings, which we’ve done plenty of before, mostly everything we tackled for Apostle was new to us! We approached them in the way we’d approach any shot – by breaking them down and figuring out, with the help of our TDs, what elements we needed and in what order to achieve them. For the vines, it was an iterative process, starting with basic procedural growth and refining it until we had something that looked plausible. But we always kept in mind that each vine would need leaves and flowers, and so we were careful to ensure from the start that the vines had seed points to which we could attach our leaf and flower geo. Conceptually we certainly had to approach these scenes with an open mind in order to produce fast growing vines that looked realistic, but eschewed the jittery nature of time-lapse photography.

How did you manage tight integration of post-production pipeline in your studio?

We used ftrack, which had some custom tools for integration of the software. Our render farm is managed with Deadline.

How did you maintain the quality of the work that you produced for Apostle?

We had daily review sessions on our large OLED display, sometimes as many as three per day to review the work at each stage. Our pipeline includes slapcomps for CG layout, animation, FX and lighting so we can see how these elements work before committing to final comp. This was also the case for our matte painting shots. We would usually render at 2K for the layout, animation and FX slapcomps, and when we were sure that everything was working as we wanted, and Gareth was happy, we could hit the button to render at 4K.

What was the most challenging shot or sequence that you did and why?

From a pure CG perspective, it was the cave explosion, since there were so many elements that interacted with each other, and I’ve described how getting the rock-fall to behave was quite a challenge! Overall though, the big vine shot was the most challenging because the sheer number of elements that were on-screen for the duration of the shot, the simulation caches we had to run, rendering that in 4K (actually greater than 4K because of the overscan caused by lens distortion) and then integrating them into the scene during compositing. We made use of GridMarkets cloud rendering for this, which freed up our render farm for other shots.

Is there something specific that gives you some really short nights?

I think because we were such a small team, and this was our biggest show, not in terms of shot count, but certainly in complexity, there were some sleepless nights towards the end when the deadline was approaching. We had a fantastic crew though, who pulled some late nights to get us over the finish line and deliver some work I’m really proud of.

What type of software did you use for Apostle?

On the CG side we used Maya for modelling, Substance Painter for texturing and look-dev, Houdini for FX and dynamics, as well as lighting in Mantra. A number of shots were done entirely in Blender.

For 2D, the Matte Paintings were built in Photoshop, and everything was composited in Nuke. One-or-two custom elements were made using Trapcode Particular in After Effects.

How long did you work on the show, what was the overall shot count, and what was the size of the team?

We worked for six months on the VFX for Apostle, completing 70 shots with 17 artists, 3 production and one IT support technician.

What’s your favourite memory of working on this show?

Other than delivering the final shot, it would be directing the stunt unit for a day in the studio. This was for a scene where the guards are being impaled and crushed by tree branches when the goddess is getting her revenge. We shot a number of stunt performers dressed as guards and suspended in the air against a greenscreen. It was great fun, describing the horrible ways that the guards were being killed and maimed, and watching them act out my directions!

Any upcoming projects of Bait Studio or other details you can share?

We’re continuing our work on BBC Casualty doing invisible VFX, and have a number of feature films that are either in development or in pre-production. I’ve also just finished shooting “Outside” with director Romola Garai, which is a character-driven horror film produced by Matthew James Wilkinson, who we’d previously worked with on “The Call Up“. We’ll be starting work on the VFX in the new year.