Visualizing the voidSnowpiercer season four hit screens in 2023. In it, the shows post-apocalyptic narrative reaches new heights of intrigue as Snowpiercer explores areas previously thought to be uninhabitable, including one scene where the train leaves its tracks and travels independently across a frozen ocean. The season also involves more action and expansive environments, meaning Image Engine was trusted with 343 shots across multiple episodes. Notable sequences included the Snowpiercer train metamorphosing into a snow tread vehicle, unveiling an epic frozen port city, a thrilling nighttime rocket launch over an icy ocean at night, and the dramatic freezing of the character Ben (Iddo Goldberg), who makes a supreme sacrifice for the safety of others.The amount of work on season four was fivefold, so there was a big difference in volume and the size of the comp team, says Jesus Lavin, Compositing Supervisor. Some of the more complex shots were those where we had to comp practical sets on huge, full-CG environments with long aerial travelling cameras. These shots were very challenging and required a lot of integration.One such environment was that of New Eden a new warm spot discovered on the frozen Earth. Image Engine built the entire valley of New Eden, ensuring it looked convincing from multiple angles. The New Eden environment shots contained multiple square kilometres of landscape with buildings, mountain ranges, lakes, and the integration of the trestle bridge and canyon from season 3, says Poser. The environment team needed to work from many different angles in full CG, but with the added challenge of combining that with plates of the New Eden set.As well as the more expansive shots of New Eden, we also worked on close-up sequences of many areas that only make up a tiny part of the environment, which we up-rezzed and refined to accommodate the need, he continues. These shots included the bridge worksite, canyon, top of the cliff, and the area west of New Eden with its parked trains and tracks.In one episode, viewers witness the camera pan over the New Eden worksite, soar across the tundra, and fly by the track scaler vehicle.This shot started with a live plate component of a crane shot that was handed off to a 3D rendering of a fly-through animation, says Jack Evans, CG Supervisor. We blended the final shot in comp with added digital matte painting elements to fill out the background. Combining these disparate elements into one cohesive shot was challenging, but our compositing team knocked it out of the park. By the end of the show, these huge environment shots felt second nature.Ali Ehtemami, Lead Compositor at Image Engine, ensured the particle and FX setups that gave these environments an extra edge in fidelity continued to be refined and improved to ensure a realistic result.The number of shots, delivery targets and the fact that we were working on all the episodes across the season made season four even more challenging and every shot was embellished with snow particles and 2D atmos and fog elements, says Ehtemami. So, to meet this challenge, I took all the great FX work the team accomplished on Snowpiercers previous two seasons and further refined and optimized the core atmos and particle tool we created for smoke, snow, snowdrifts, clouds, and fog in Nuke. I tweaked the setup in a way that kept the quality of the particle setups high while running at least ten times faster. Moreover, we introduced a new modular compositing workflow specifically tailored for this show, coupled with various optimizations implemented in the compositing process. These advancements greatly contributed to enhancing production efficiency!Embracing complexityOf course, the Snowpiercer train itself did not go without its fair share of attention in season four. This time, the trains visual effects required a significant increase in mechanical complexity as well as further optimization of the train track tool, as Poser describes.For season four, the tool could: generate better wheel alignment and displacement and connect wheels correctly on the train track, even when the track was curved or sloped; correctly link the train cars; create better train car spacing with support for steep angles and curves; and improve instancing for performance and caching, he says. By this point, the tool was firing on all cylinders and saving us time which the team could then spend on creating even more beautiful, believable shots.Those shots included some close-ups of Snowpiercer that revealed the train in more detail than in any previous season. One close-up sequence sees the character of Ben stepping outside the train to release a stuck link between two train cars, and in another, Melanie (Jennifer Connelly) must crawl through the trains undercarriage and into the cooling vents. For these scenes, the Image Engine team had to construct the Snowpiercers intricate undercarriage with numerous moving mechanical pieces and higher-resolution textures.The most challenging setup was definitely the close-up shot of the undercarriage of the train where the tank-like treads are first revealed, which enable Snowpiercer to leave the tracks and travel independently across the frozen ocean, says Evans. The team had to design a believable system that could deploy snow treads across the whole train, lift it with hydraulic pistons and allow Snowpiercer to leave the track and freely drive through a ruined port city and onto a frozen ocean.To create the sequence, Image Engine created concept artwork of the undercarriage design for approval, then built out the treads and their animation, ensuring the mechanism felt like something that could realistically propel the train. Our animation supervisor, Curtis Richardson-Smith, created animated mockups of modified geometry for the mechanism used to link the cars together, which the asset department then used to build out the more detailed work, explains Evans. Ultimately, the close-up shot revealing all of this was a cross-department effort involving assets, animation, FX, and compositing. When it all came together, the results blew me away.Making the unreal, realImage Engines task list for season four also encompassed numerous shots of actors against a green screen, such as some scenes that show characters moving around on the exterior of the Snowpiercer train.The biggest challenge on shots like these is always integrating something shot on stage to make it look like the actors are actually on a train driving 150kph and rumbling through a frozen world, says Poser. This is an even bigger challenge when the actors are very close to the surface or touch and interact with the CG train, like Melanie hanging onto the ladder on the side of Snowpiercer. There are an incredible amount of details and small things to get right, or else the shot will look fake. These sequences require flawless execution from matchmove and roto to lighting and final comp.Lavin adds: When dealing with blue screen material shot on set, the challenge is finding a middle ground between the look that comes with studio lighting and the lighting you need in your CG to make the shot look good. Nevertheless, our Image Engine lighters are amazing at tasks like these at this point.Image Engine also updated and optimized its tools to more easily incorporate 2D elements on cards within its 3D scenes. These updates gave us a lot of flexibility in quickly trying out different ideas without involving the compositing team every time we wanted to combine practical elements in our CG environments, says Widen.Many scenes across Snowpiercer season four also required the addition of digital doubles CG replicas that needed to feel as believable and natural as their living counterparts to sell the believability of the set pieces in which they featured. When you have a full CG shot with digi-doubles, most of the workload is on the shoulders of animators and lighters, says Lavin. Again, at this point, the team is fantastic at making these shots feel real. Our artists delivered some incredible work.