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A Discovery of Witches: Creating VFX for the Sky UK Series

Members of the REALTIME team talk about creating mythical creatures for TV production and discuss the process of designing realistic smoke and fire VFX.

Introduction

80.lv: Could you give a little intro to your team? What do you specialize in? What projects have you contributed to?

Ian Jones, CG Supervisor: REALTIME has a long-established reputation for creating high-end, pre-rendered game trailers for some of the largest video game titles around. Over the years we have developed and honed our skill to create both realistic and fantastical action sequences. Characters, monsters, aliens, explosions, magic, cities, spaceships — you name it, we’ve done it. And all in beautiful high fidelity eye-watering CG.

While we were firmly rooted in game trailers, many of our artists and supervisors were from a film and TV background and there was a growing desire to stretch our wings and demonstrate what we could bring to the broadcast world.     

As a studio, we have dabbled in TV for a few years, usually picking up individual shots or short sequences for shows such as Year Million. Our expertise in creating realistic character-driven sequences soon led to our first large title, a show called Mummies Alive for Impossible Factual and The Smithsonian Channel. We depicted the lives and deaths of a variety of unfortunate souls who were eventually to be unearthed, centuries later, as mysterious mummies. Through our tried and tested character pipeline, we used photogrammetry and motion capture to bring the grizzly events surrounding their deaths to life. 

REALTIME’s relationship with robots, aliens and explosions led us to become the primary VFX vendor on the BBC’s War of the Worlds, where we had great fun raining terror over an unsuspecting Victorian Britain. As well as towering tripod and murderous Martians, we were responsible for digital matte paintings, set extensions, and a healthy dose of destruction.

Working on A Discovery of Witches

80.lv: How did you start working on VFX for A Discovery of Witches? What were your goals?

Ian Jones: Through a variety of projects, we started to build a reputation for solving both creative and technical problems. As pre-production began for A Discovery of Witches season two, Bad Wolf’s Stephen Coren (Production VFX Supervisor) and Antony Bluff (Production VFX Producer) asked us to develop concept art and 3D previs for a variety of magical effects, which we went on to complete in the show’s post-production.

Emily is “scrying” magic features throughout the new season. There had been hints of this magic previously, as we had seen glimpses of her ability to manipulate wisps of smoke and conjure up ghostly images. We were asked to develop and strengthen her power across multiple episodes until she was ultimately able to summon and communicate with her dead friend, Rebecca. Working closely with Coren, we sought to avoid all the usual cliches and create something that, while appearing unearthly, would still feel grounded in the natural world. 

Our second, more daunting task, was to explore how Corra might be portrayed in the show. The appearance of Diana’s familiar, a firedrake, would be hotly anticipated by fans of the books and a major event in the series. Again, it was important that despite being such a spectacular character, Corra should feel natural and sit believably within the real world.  

Choosing VFX Software

80.lv: First, what tools did you use for production? Houdini is a must. What are the other tools? What did you use the tools for?

Ian Jones: Traditionally, REALTIME has been a 3ds Max facility. Much of our scene assembly and rendering happens in 3ds Max with V-Ray. However,  our toolset has grown considerably in recent years. Our character pipeline is now focused around Maya and the majority of our asset creation takes place in ZBrush and Mari. While the vast majority of our visual effects are now created in Houdini, 3ds Max still plays a role in our VFX previs with tyFlow. All final compositing takes place in Nuke. 

Creating Effects and Simulations

80.lv: You had to set up a number of smoke simulations and particle effects, right? Please tell us about your workflow. How did you set up initial forms and polish everything? What were the challenges?

Ian Jones: When creating an effect that will be used across multiple shots, scenes, or even episodes, it is important to establish the basic form, movement, and timings before any fine work begins. With Emily’s scrying scene, we wanted the audience to understand that her skills are improving and her connection with Rebecca is growing stronger as the season progresses. This meant working closely with the show’s creatives, with the emphasis on speed of iteration. Starting with the live-action plates, we used simple particle systems and basic geometry within 3ds Max and tyFlow to generate a rough indication of the effect and used After Effects to quickly integrate the elements with the footage. Once the performance was locked, we were able to move into Houdini to develop a more sophisticated approach.

When dealing with physically accurate simulations, it can be relatively quick to get your first result. But this result also needs to be directable. This is the difference between a nice test and something that is commercially viable. Clients want to see iterations and make subtle tweaks. If your approach yields wildly differing results from the smallest of adjustments, both you and your client will become frustrated. We break our simulations into manageable phases and introduce rigs and controls which allow our artists to manipulate the simulation at various stages.  

For the column of scrying smoke which reveals Rebecca, we initially generated the tendrils along linear paths, and then warped and wrapped them into position using a rig. This rig allowed us to control how the tendrils grew and developed throughout the shot. Once we were happy with their performance, we added secondary and tertiary simulations to soften and blend the forms as well as introducing weight and buoyancy to the smoke.

Creating Magical Creatures

80.lv: You also worked on creatures for the show. Please discuss working on them. How did you turn concepts into final creatures? 

Ian Jones: Corra the Firedrake was a real voyage of discovery for us. We started with a few lines of description from the book and worked closely with Coren to explore how she should be portrayed. The firedrake is an ancient mythical creature, and there are various depictions of it in historical artwork. While these depictions weren’t something we would want to follow too faithfully, they did contain elements that we felt would help set our design apart from other flying fiery creatures. We created a variety of sketches and concepts as we iteratively developed the character of Corra.  

We needed Corra to have a discernible surface. We felt that the drake should be covered in a combination of scales and feathers and that these should be portrayed as flames. We decided that these should be more akin to gas jets than burning coals and so we explored a variety of burning chemicals as well as different intensities of ignition. After a great deal of reference gathering and research, we happened across a video of a giant ball of burning matches. The combination of intense chemical ignition, followed by ribbons of fire which then settle into soft licking tendrils, was exactly what we needed. And so this became the visual benchmark for our look development within Houdini. 

We sculpted the character and rigged her in a conventional manner before taking the asset into Houdini. The foundation of her flame simulation was created in her T-pose. This allowed us to direct the length and orientation of her flames, adding specific forces to different areas and iteratively refine her overall form. This was to become our base asset which would be used across all of her shots. Animation would then manipulate and deform this initial simulation to create her performance.

Nicolas Seck, Animation Director: The animation was executed by a very small team of extremely talented animators including John Batchelor (Corra, birds' fight, snakes, egg), Nick Pavlov (Corra), and myself on the Corra sequence. 

We had the opportunity to work on a variety of creatures that were all driven by magical powers: Corra the firedrake, birds of prey, snakes, and even a flying egg. This gave us the chance to explore different types of performances. 

Corra is a mythical creature with no real equivalent in our world, so we had a degree of creative license to play with. However, she still had to evolve in a real-world environment and interact with the actors, so we had to be careful to preserve the believability of her motion. We could not go too far into fantasy.

At her most basic, Corra is a large bird made up of fiery feathers. The intensity of the fire could be adjusted according to the mood of Diana, her mistress, who manifests Corra to protect herself when she’s under threat. When a gun is pointed at her, Corra bursts out just in time to shield Diana’s body with her wings, deflecting the bullet. At that stage, Corra is a defensive creature but then she takes off and switches to attack mode, with a more intense fire flowing off her body as she’s circling the attackers and blocking their escape. 

Corra is based on historical drawings of a firedrake, and the client wanted to preserve the unnatural positioning of her limbs from the original concepts. This was a challenge as Corra not only had to fly but also strike a resting pose after landing. We worked closely with a talented rigger, Florian Friedmann, to find the best solution to make the deformations work despite being different from the classic hip/spine/chest structure. Corra's body was quite compact but still needed some range of flexibility, particularly for her landing moment.

We also had to set a bone for each feather which made the HD rig quite heavy to handle, but fortunately, Florian provided us with a more animatable version. The wings and the tail were quite long and flexible which gave us the ability to add an element of majesty to her when she flies around and fully stretches her wings. 

Diana conjures snakes from an intricately embroidered slipper and from a drinking glass. For those, the goal was to give a nice transition from the objects to the real snakes. The rigs were fairly simple, designed by our Lead Animator, John Batchelor. We progressively inflated the mesh of our CG snakes to give them more volume and detach them, to allow them to seamlessly transition to a shot where the real snake would take over. 

The birds of prey sequence featured a partridge, a hawk, and a kestrel. The rigs were designed by Florian Friedmann to respect, as realistically as possible, the anatomy of each bird. They had to be complex enough to allow us to get the intricate shapes that the fight between the birds implies. The biggest challenge for this sequence was to make the fast movements readable, as the natural camouflage color of the birds made them difficult to stand out in the forest environment.

We choreographed this scene so we would have enough changes in lighting and silhouettes to catch the attention of the audience at the appropriate moments. When the birds eventually collide, we created a sense of chaos and drama by introducing some twirls in the trajectory, adding falling and detached feathers. We carefully chose the moments that the flaps/slaps happen, so they are clearly readable and show that both birds are still alive.

Lastly, we added a sequence where Diana demonstrates her magical powers with a magic egg. The egg takes off, spins, and shakes until it eventually lands on a table and a chick comes out of the broken shell, showing that the maturity process has been accelerated by magic. There were no major complications for rigging this one, but the difficulty was more about finding the right number and frequency of the spins to make it understandable, particularly if you appreciate that an egg is plain in terms of detail. The progressing decaying of the egg helped us in that respect.

The Art of Creating Believable VFX

80.lv: When working on effects for such fantasy projects one of the main challenges is the believability of the final effects. How did you make sure that your simulations feel real? What are the tricks here?

Ian Jones: The trick is to, wherever possible, keep it real. We scanned lidar data on set and created photogrammetry. We captured spherical HDRIs and recorded the values of any contributing interactive light. When simulating we tried to work within real-world scales. We rendered fire with true values using the blackbody shaders. All our reference and methodology was based on things which could occur in nature, even though the majority of our subject matter was magical.   

Nicolas Seck: Believability is at the core of photoreal VFX animation. The first step is always to try to establish the creature’s style of motion and generate some tests (usually some motion and idle cycles). We also rely on video references of appropriate actions for the scenes and try to select some interesting examples which go on to define the natural performance for an existing creature (e.g., our birds of prey and the snakes) or inspire us for the more fantasy ones (like Corra).

An important part of what we do is to get a clear understanding of the expectations of the client, early on. For A Discovery of Witches, we had to fit the creatures in the plates provided by the client which had specific timing imposed by some camera motions, lighting changes, and the performance of the actors. We did some initial blocking, to confirm that we were on the right track.

Then it was about adding details and elements which give a flavor to each shot. This meant trying to find, in the raw footage, guidance for the performance of the creature as if it had really been there during the shooting. For the Corra sequence, we also had the challenge of having to hide a technician who was holding a lamp on set. Fortunately, Corra was not only generating lots of flames but was producing lots of smoke too.

The main trick is to find the appropriate energy, the correct flow with clear and expressive poses. It sounds easy but it requires lots of patience and constant communication with the animators and the client to avoid losing time by going in the wrong direction. If that is managed properly, that should give you the extra resources to finesse the details and enhance the result.

The Main Challenges

80.lv: What were the main challenges during production? What lessons did your team learn? What was your favorite part?

Ian Jones: In early tests with Corra, it became apparent that a creature made entirely of fire would be extremely hard to read on the screen. Fire is an additive visual element. When her wings passed in front of her legs, the fire values would combine with confusing results. This was essentially a sorting issue as there was no way for the eye to read whether the wing was in front of or behind her leg. This is only compounded when the character is emissive and the primary light source in a scene. As she flew close to the cave wall, the wall would be illuminated and the character would become lost.  

The answer was negative space. First, we identified that smoke could help separate Corra from the backplate, and to some degree, it helped add depth within the shape of her body. But we needed something more, something that would give Corra a more defined surface and allow her to occlude herself. And so we created dark fire. We repurposed the “feather” solution, giving them a dark material, and scattered them between the original feathers.

They were more than just smoke, they had a sharper form that contrasted and complemented the original feathers. At this point, something exciting happened. The physical intersection of these two types of feathers created a texture and fidelity which we were not expecting. The emissive flames illuminated the dark feathers which cast shadows on themselves while also concealing any flames behind. Suddenly Corra had form.      

REALTIME, Animation and VFX Studio

Ian Jones, CG Supervisor

Nicolas Seck, Animation Director

Interview conducted by Arti Sergeev

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