Frozen in Time No More

Well, Disney just couldn't "Let It Go." The "It," is the animated feature Frozen, which set off a flurry of devotion around the globe and broke all manner of historic box-office records following its 2013 debut. So, what would lead Walt Disney Animation Studios to venture "Into the Unknown" and risk making its first-ever musical sequel by revisiting this mega-successful film? The answer is simple. There was more story to be told.

One question that returning producer Peter Del Vecho was asked repeatedly following the original Frozen was, where did Elsa get her icy powers? Also, where were the sisters' parents headed when their ship went down? And, is there really such a thing as "happily ever after?" As it turned out, returning directors Chris Buck and Jennifer Lee were wrestling with those questions as well. "We realized there was more story to tell. Frozen's ending was really just the beginning for Anna and Elsa, newly reunited as sisters," says Del Vecho. And thus, another journey began.

On November 22, Frozen 2 blew into theaters, as the beloved sisters Anna and Elsa, along with Kristoff, Olaf, and Sven, leave Arendelle and journey deep within an autumnal forest in an enchanted land to uncover the source of Elsa's powers in order to save their kingdom. But, there are some dangers that Elsa must face alone.

"Six years ago when Frozen was released, we could never have imagined how much that film would mean to people of all ages. How it would resonate with audiences around the world. We've never for one moment taken that for granted," says Del Vecho. "And that's how we approached Frozen 2. At Disney Animation, we never make sequels unless the filmmakers themselves have an idea for a film and a desire to tell it. That's why even though Frozen 2 is our 58th animated feature, it is only our fourth sequel, and the first animated musical sequel that we have made, at that."

Also rejoining the creative team are the original song writers and warblers, and of course, the voice cast, along with many of the artists and animators from across the various departments.

Frozen 2 picks up three years from when we last visited with the characters, who are now good friends. The season has evolved from winter to fall. The gates to the city are now open. The characters have matured. Elsa has become more confident and comfortable with her powers, while Anna has her sister and her happily ever after. Kristoff is in love with Anna, and Olaf has become an avid reader and seeks answers to more grown-up questions. However, Elsa becomes unsettled, hearing a voice calling to her that only she can hear. When danger envelops Arendelle, Elsa and the gang set out to make things right, guided by childhood stories told by the sisters' parents of an Enchanted Forest that may hold the answers they are looking for.

The film, epic in scope and scale, is steeped in the imagery and folklore of the Nordics, influenced by Del Vecho, Buck, and Lee's own journey to the enchanted lands of Norway, Finland, and Iceland. According to Buck, there was a stark contrast between Norway and Iceland that framed the film's concept for them. "The character of Anna felt home in Norway, with its fairy-tale settings, but Elsa felt strangely at home in dark, mythic Iceland," he says. "We realized on this trip that Anna is your perfect fairy-tale character; she's an ordinary hero, not magical. She's optimistic. Whereas Elsa is the perfect mythic character; mythic characters are magical. They carry the weight of the world on their shoulders." Mythic characters also often meet a tragic fate. And fear of that tragic fate was something Anna has been worrying about and trying to protect her sister from.

A YOUNG ELSA AND ANNA HEAR TALES OF AN ENCHANTED FOREST FROM THEIR FATHER, THE KING.

Characters

Frozen 2 opens with King Agnarr telling a young Anna and Elsa a "true tale" about a real enchanted forest he visited as a boy that was ruled by the magical spirits of nature: air, fire, water, and earth. Sometimes these spirits can be enchanting, other times dangerous. During that visit, something went wrong and enraged the spirits. He wasn't sure how, but he escaped, barely, after hearing a haunting voice crying out and glimpsing a magical mist that enveloped the forest. The king warns the girls that the forest may wake again.

This warning appears to have come to fruition, as the sisters and the friends make their way to the Enchanted Forest, which no one has entered, or left, since that fateful day of the young king's visit. Here in the Enchanted Forest and later in the Dark Sea, we find a range of unique characters, many inspired by old Norse myths and folklore of the Nordic region.

Effects and animation worked very closely, especially since there are some characters that required the departments to develop new workflows and work collaboratively with other departments to bring the characters to life, says Becky Bresee, head of animation. This is particularly true of Nokk and Gale. It also extended to Elsa, as she becomes more forceful in releasing her magic from her fingertips.

In this film, the family is together now, so there are more characters in the scenes, as opposed to the original, which often featured just one in a shot. "Not only do they all have to have motion, but more importantly, emotion," says Bresee. And, there were a lot of long shots to animate - most were 30 seconds or more, with the character barely moving, just emoting.

"It's animation gold, though. There aren't many opportunities for an animator to get to work on shots like that, and this movie is full of them," says Marlon West, head of effects animation.

Anna, Elsa, and the Gang

The central figures of Anna, Elsa, Kristoff, Olaf, and Sven have returned in Frozen 2. Although the artists jumped onto the sequel shortly after the original film had debuted, a lot had changed technologically in that span of time, requiring updates to the models.

Of course, one of the most noticeable changes to the characters, particularly the sisters, is their new costumes, which are more suitable for travel and whose colors are more complimentary to the fall season. Designing the wardrobe for the characters was no light affair, requiring many iterations to the garments, the details of which are astonishing. Yet, the design of the clothing had to work hand in glove with animation, enabling the characters to move unhindered under strenuous motion.

"The outfits are complex and challenging from a simulation standpoint," says David Suroveic, technical animation supervisor. "They are multi-layered, heavily detailed with items like beads, gems, and embroidery, and contain a significant amount of fabric. Multiple layers are always challenging because they are complicated for the solvers to simulate, complicated for the artists to clean up, and have to perform in a stylized way."

According to Suroveic, dressing Anna in pants and a dress, with a cloak on top, resulted in the densest model they had on the film and, therefore, the most challenging to manage when she was extremely active. "It might be a heavy, inhibiting outfit in terms of motion, but we still have to make that work and move gracefully," he adds. Elsa, meanwhile, is in lighter, more ethereal clothing of tulle and silks.

Kristoff's outfit visually looks similar to that from the first movie, albeit with a few different color schemes and embroidery details. However, the underlying tech was updated, giving his outfit an entire re-tailoring to better fit his body, thanks to the use of Marvelous Designer, a 3D tool for designing clothing and fabrics, which actually tailors clothes to the body. (Previously, the animators used traditional 3D modeling techniques.) His hair, too, went through a full redo in terms of grooming. "We made advancements in both our grooming technologies as well as our hair simulation technologies, making some big improvements that we wanted to fold into that here," Suroveic says.

As a result of the advanced technologies, the tech animators also significantly reduced the amount of Elsa's hair, while still making it appear as rich and lush as it had been in the original movie. It was also simulated with fewer curves, resulting in faster sim times. In fact, Elsa sports a few hairstyle iterations this go around, as opposed to just her single braid.

Anna's hairstyle, however, changed from the signature double braids to a complicated braid with her hair hanging curly and loose below the nape of her neck.

Just as the cloth and hair sims became faster, so, too were the Autodesk Maya animation rigs, including the facial rigs, giving animators more opportunity to iterate. Since this is a musical, the animators strived on getting the body mechanics of the singing accurate - all the little breaths and intakes - as well as the facial expressions. Thus, more controls were added, enabling animators to regulate the way the characters breathe, the different muscles that would engage not only in the face, but also in the neck and torso. "A lot of detail goes into every breath on this film," says Suroveic.

Because the crew already had built a particularly complex rig for Olaf that allowed him to rearrange himself, very little change was made to it. As for Sven, advancements in how the artists groomed and shaded fur, as well as simulated it, were applied.

ADVANCES IN HAIR AND CLOTH WERE SOME OF THE UPDATES TO THE RETURNING CAST.

Gale

Gale from the Enchanted Forest was one of the film's most unique characters. "It was one of the first characters the directors asked me to work on, and my first question was, how do you draw wind?" recalls Bill Schwab, art director for characters. "How do you draw something that isn't there?" Formless, Gale's presence in a scene is announced by the impact it has on other objects in the scene, such as movement of leaves, debris, sticks, and so on. As a result, early planning was required for each scene.

"We realized very quickly that Gale would be a very collaborative character, a multi-discipline, multi-department effort," says Trent Correy, animation supervisor. "We'd be working with effects, tech anim, character animation, rigging, environments, lighting…everyone." However, typically the workflows had some of these departments way upstream or downstream from animation, a situation that had to be remedied so they could work collaboratively on scenes involving Gale.

A new in-house tool called Swoop was developed to give artists the ability to animate the path and the timing of the wind spirit. Animators could work with these paths directly in Maya, or they could record the path and timing with the set using VR.

"There were tools to basically get onto a VR capture stage and block out a path for the wind to travel around. That would then drive the rig, helping visualize both the speed of Gale, the size of Gale's effect, and any noise or turbulence that it would provide as it's passing by, such as airflow and current," explains Suroveic. "From there, effects and tech anim would iterate in terms of how much environmental debris Gale should pick up and move along with it, whether that's leaves, flowers, or seedling pods."

The result was then passed along the pipeline so other departments could start working on the scenes.

Another option was to use hand animation to determine the amount of leaves and debris Gale picks up, attached to the path sketched out as a guideline for effects to then simulate any extra debris added to Gale's path. "We wanted to make sure you couldn't tell which leaves were hand keyframed and which came from effects," says Ramos. "It had to be seamless."

The group could also track Gale's movement through a scene without those environmental factors. "We could tell where Gale was at any given time based on how the other characters were moving," Suroveic says of the work by tech anim.

THE EARTH GIANTS ARE MASSIVE AND MADE OF STONE, THUS HARD TO ANIMATE.

Earth Giants

Another interesting set of characters from the Enchanted Forest are the Earth Giants. Representing the earth spirits, they are asymmetrical, massive in scale, and made of stone, so they were extremely heavy and difficult to move around. "In addition, we had to make these characters feel like they were actually moving and breathing," says Tony Smeed, head of animation.

Instead, Wayne Unten, animation supervisor for the Giants, and Chris Pedersen, rigging supervisor, devised a way for the rocks to slide around, rather than bend, thereby preserving their stone-like structure. As Suroveic explains, the models were segmented into multiple plates of geometry, then it was a matter of making sure those plates were colliding and sliding with each other.

A WATER SPIRIT, THE NOKK REQUIRED A LONG DEVELOPMENT PERIOD.

The Nokk

A water spirit inspired by old Nordic myths, the Nokk is a warrior creature, a protector of the Dark Sea. It is literally a horse made out of water. Like Gale, the Nokk required a long development time with multiple disciplines working together: tech anim, effects, and then lighting. The most collaborative sections of the Nokk were the tail and mane, which especially described the water element of the horse.

"Even though this character is big and powerful, we wanted to balance that with a delicate quality, which is what brings grace to this character and makes it mythical and magical," says Suroveic.

Animating the Nokk was a two-stage process. Animators used their horse rig to create a realistic performance for the character. Meanwhile, tech animation performed the sims for the mane and tail using its traditional hair solver, with the knowledge that at some point each individual strand would get lost and read as a sheet. Then effects took a pass of remeshing the hair curves from tech anim into the water volume, using volume-based fluid simulations within SideFX Houdini's Ocean tools and its FLIP solver.

"Here at Disney, one thing that makes our process so special are the draw-overs we hand animate on top of our simulations," notes Suroveic.

Volumes and fluids then were attached to the character's surface. Effects further explored how much spray and other elements could be added to make the horse feel like it was part of the ocean. "It left behind foam patches as it is galloping in the sea, having spindrift and mist blow off its mane," says Erin Ramos, effects supervisor. Interior bubbles and volumetrics within the character's interior gave it life. A slight animated noise pattern on its body made the body feel less solid and more dynamic, as water is flowing constantly on the surface.

"The biggest challenge was to always make sure we preserved the performance from animation, to make sure its face was clear and you could see its expressions, nose, and ear movement, yet it still felt like this character was fluid, dynamic," says Ramos. "It's difficult to read expressions on a character that is transparent."

The animation, however, was complicated by the Nokk moving above the water and below the surface, as well as its intricate interaction with Elsa.

"We had to make the galloping on top of the moving, raging waves believable, since this is not something you see in life. And we needed a very efficient workflow between the departments," says Svetla Radivoeva, animation supervisor. "So, right after animation, our first pass was done on top with draw-overs. This was the easiest way to determine the length and performance of the tail. Then it went to tech anim, where, with much more information, they could apply the curves in an actual Maya environment. This is a moment where, since everything is almost completely simulated, you see what's working."

In all, it took approximately seven months for the groups to see the results for the first time. "We couldn't see the final result until it went through all the departments and through lighting. That's when it really came alive for us," says Ramos.

FROZEN 2 REPLACES THE FROZEN LANDSCAPE WITH FALL COLORS.

Environments

The environments in Frozen 2 are much more than backdrops; they are integral to the overall storytelling. The Frozen 2 artists expanded the world they had established for the original film, building on top of it - removing all the snow to reveal the design concepts underneath. "The verticality was something we held onto, whether it was a tree, a piece of furniture, even the stave part of the castle," says Lisa Keene, co-production designer. Color was also important, moving from a jeweled palette to one that is on the warmer side of the spectrum, skewed toward magentas and reds.

Like the characters, some of the environments in Frozen 2 were inspired by the research trip to the Nordic countries, particularly the fairy-tale setting of Finland and the mythic land of Iceland. The scattering of rocks that look as if they could have been tossed there by giants. The black sand of the black pebble-stoned beach in Iceland that makes the perfect shore for the Dark Sea.

What's more, the environments had to feel alive, accomplished with some new tools inside Houdini, including its Vellum Solver.

Arendelle

This movie travels throughout the entire village, as opposed to the first film, which introduced only isolated areas. This time, the camera moves from one location to another, so the artists approached the layout from a city planning perspective in terms of logic, finding the ideal locations for objects introduced in the first film, such as the clock tower. In fact, Arendelle is mainly handcrafted, with the buildings hand-placed. Environment artists then gave the village a sense of history.

"It feels much more like a real town that you can actually walk around in and visit," says David Womersley, art director of environments.

Next, the artists had to ensure that imagery appearing in the background in Frozen would stand up in close-ups in Frozen 2, leading to renovations and resurfacing of the models to bring them up to the current technological levels. "Our tools are so much better now than they were for the original. There's so many more options to add little details that give it a richness," says Sean Jenkins, head of environments. In addition to giving Arendelle a paint job and changing all the hues on the buildings to reflect the new fall season, the artists also decked out the town with banners, bunting, wreathes, and so forth.

Enchanted Forest

A forest can be very complex to create - particularly one that looks natural, has a sense of place and history, and also lives in the Frozen-style language. The designers began this daunting task by taking their cue from Sleeping Beauty's Eyvind Earle, who created sculptural deep spaces among myriad plants, and then layered the verticalities over top for that film. "We grabbed this idea and built our forest in a way that's stylized, that feels organic," explains Keene.

Although the studio has used vegetation tools in the past for movies like Zootopia, it needed to build the Frozen 2 environments at a larger scale with more complexity; they also had to be art-directable and efficient. To this end, the group worked with software engineers to determine what improvements were needed to their existing tools and what new tools were required in order to build the forest and enable the required interactions and effects.

When it came to constructing the forest, the artists created it in stages, building so-called vignette groupings, then they added other islands to that until they built out the world. "That way you have a sense of design that's consistent, and you feel it all the way through the forest," Keene says.

As Womersley notes, trees can be tricky - they can look beautiful from one side, but if turned just a few degrees, they might not look so good. To avoid this issue, the designers worked with the modelers to make sure the islands looked amazing from every angle. In all, a dozen to 20 islands were crafted.

Before creating the groupings, though, artists acted as botanists, researching the appropriate trees and flora they would use. Artistic controls enabled the team to create a gradation of color across the trees; the leaves themselves were instanced to lighten the scene. In all, the artists grew 50 to 100 unique trees, which numbered in the hundreds for some scenes, and in the thousands and tens of thousands in the larger forested areas.

"The one thing about the Scandinavian region is that fall is not only in the trees, but also on the ground. The ground cover turns brilliant colors," Keene points out. "We had color everywhere, and then we had to organize it and get our characters to read over it [in scenes]."

Not only did the artists have to generate all the ground cover and vegetation, but they also had to account for ambient motion and ground interaction of the characters kicking up leaves, as well as the leaves swirling around in the wind, and how that interacted with the trees themselves. "It's easy to place leaves on the ground, but to have the leaves move around realistically and not have them go through things or pop around and look fake, that was the difficult part," says Tad Miller, technical supervisor of environments. When the trees had to bend or shift based on action, effects would step in and make the vegetation move accordingly, while animation created the character performance.

"[Effects] had controls, almost like character rigs, on the trees, causing the tree to bend, flex, and so forth, and then they fed that back into the environment for the shot," Miller explains. "They took the static data from the environment, ran it through a simulation that moved the trees, branches, and leaves, then they sent that information back into the environment as an animation." This was done using custom and off-the-shelf tools, such as Houdini and Maya.

The artists also inserted large outcroppings of rock formations, common to the area, throughout, creating groves, like they did for the trees, using procedural techniques. "We were hand-placing tens of thousands of trees, bushes, and saplings, not to mention all the rocks and ground cover," says Jenkins. Larger rocks, particularly those on which characters climb, were individually crafted, and artists used a whole other suite of tools to populate these assets into the environment. These include: Bonsai for vegetation modeling; Droplet to paint and interactively scale and reposition vegetation; Aurora as the processing engine; XGen to procedurally grow rocks, leaves, and such; and Hyperion for rendering.

To add atmosphere and push back some of the environmental objects, the artists added layers of mist, which is a naturally occurring element in such a forest, but in this film, it is a conceit that is narratively important. Lighting also played a big role in adding a magical feel, as was the way in which the camera was placed. "It's really a combination of artistry across modeling, look dev, effects, lighting, and animation," Miller adds.

EFFECTS AND ANIMATION WORKED CLOSELY FOR THIS SCENE: ANIMATION PERFORMED ELSA, WHILE EFFECTS HANDLED THE WATER SIMS, INCLUDING THE GIANT WAVE.

Dark Sea

Unlike the water in Moana, which was calm and clear, the water in Frozen 2 is dark and turbulent. When creating the Dark Sea, the group wanted it to feel mysterious, but also dangerous and treacherous. And since the environment is pretty much all water, effects had to work closely with the production designers to establish this look.

The crew also needed waves that were big enough to feel like they were a threat to Elsa. For this, effects used mathematical equations to model the motion of the waves, and plugged those into their simulation, tweaking various values for amplitude and wavelength, and ran the sim to see the result. The tests showed how the change in ocean topography affected the break of the waves. The goal was to get waves that were several times the size of Elsa.

"A simulation wants to be based on reality, and sometimes, especially in our fairy tales, we want to break that reality, and that's when you get into a conflict between the technology and the art, which we had to solve here," says Miller.

Once they got the waves at the right size and frequency, the group wrote a separate simulation for the shoreline to limit how far up the beach the water traveled after it broke, running two different simulations to get the big crashing waves and the ensuring shoreline rush. These were then combined and composited with the procedural ocean surface that extends out to infinity. The water motion, however, remained raging, violent, with lots of foam.

Says Ramos, "We were running much bigger sims on this show. We had to make these huge, breaking waves that are fully simulated."

Without question, the challenges presented in Frozen 2 gave the effects department some new and interesting problems to solve. For instance, Elsa had to run on top of this water, and she is using her magical powers, creating an ice ramp of sorts - so now there is water and ice, a fluid and solid, built (and fractured) by effects. Animation had to perform Elsa, but the water simulations, including the giant wave, were coming from effects. This required an especially tight loop between animation and effects. However, the effects department typically follows animation in the pipeline.

"But because we were essentially supplying the ground plane on which Elsa was running on, we had to get ahead of layout even, to provide them with some rough simulations just to get an idea of timing and the speed of the water she would be interacting with," explains Ramos.

Alas, the tricky thing with having a simulation as the ground plane was that every time a little change was made to the surface, it changed the entire thing. So, effects animators had to work closely with the animation team to make sure Elsa's performance was in sync with the performance of the water, and vice versa: Not only does Elsa react to the water, but the water had to react to her as well. "It's pretty hard to tame simulations. For this, though, we had to get the right size of these waves, the scale, and nailing that was a big challenge here," Ramos points out - as was all the back and forth between effects and animation.

To be sure the shot would work correctly among the various departments, effects ran low-res sims and mock-ups of the wave toppling over and breaking, and gave them to layout, so they had an idea of the timing and where to place their cameras. Meanwhile, animation provided Elsa's performance, which had to be tracked on the moving wave and matched with the breaking of the wave.

ELSA HAS MORE CONTROL OVER HER MAGIC THAN SHE DID IN FROZEN.

Effects

It is extremely difficult to separate effects from character animation and even the environments in this film. Furthermore, Frozen 2 contains diverse types of effects, and lots of them, whereas the first Frozen centered mainly on snow-related effects. "Because this was an effects-heavy show, we were everywhere - environments, lighting, layout, animation," says Ramos.

Moreover, while many of the simulations in the film were based on real physics, and the artists strived for believability, they did not want photoreal effects. "Our characters are caricatured, and we wanted the effects caricatured as well," says West. "We were always pushing and pulling the simulations." Yet, it's far more than just physics-based simulations; there is a lot of artistry that went into creating the sims, too.

In Ramos' opinion, the most challenging effects were those pertaining to water. "Not only do we have ocean waves and shorelines to deal with, but we also have a water character, Nokk, made completely out of water," she says. "We had to figure out how the character looked above the water and below the water, to make it feel like it's still part of the water." Adding to the complexity, of course, was Elsa interacting with the water.

"I feel like the theme of this movie, effects-wise, was 'collaboration.' We keep saying that because it's no exaggeration. It took many different teams working together to bring these characters, some of which are abstractions of elements, to life," says Ramos.

Effects also handled Elsa's magic, most of which was also generated in Houdini. "She's more controlled with her magic, she's very conscious of what she is doing now," says Ramos.

Fairy-Tale Ending

Four years in the making, Frozen 2 is, ultimately, a mythic fairy tale about home and family, self-discovery, courage, and the power never to give up.

In essence, the property has two different stories: the mythic story (Elsa) and the fairy-tale story (Anna). Had the mythic version prevailed in the original Frozen, Elsa would have suffered a tragic fate. But the fairy-tale Anna saved the day. "The power of these two in a tug of war was the biggest discovery for us," says Lee. "And that really came from our research about the difference between a myth and a fairy tale."

For fans around the world, thank goodness the fairy tale prevailed, giving us Frozen 2.