Strong characters, immersive environments and a ripping 70s soundtrack - that’s Marvel’s latest film Guardians of the Galaxy in a nutshell. With two main characters that would be realized entirely in CG, and with vast space and earth-like environments to create, the visual effects crew were once again crucial to completing the film. Overall visual effects supervisor Stephane Ceretti, associate visual effects supervisor Olivier Dumont and visual effects producer Susan Pickett guided the ship. They lead a vast army of VFX artists from 13 companies including MPC, Framestore, Luma Pictures, Method Studios, Imageworks and an in-house unit, plus previs/postvis teams from Proof and The Third Floor. fxguide takes a look at just some of the major sequences.
Central to the film were the characters of Groot and Rocket. Knowing that the tree-like form of Groot and the feisty Rocket - a genetically modified raccoon - would not only pose technical challenges but also need to be treated like any other performer, production arranged for several vendors to contribute animation tests. “We had some concepts and we shot some plates with a small crew,” says Ceretti. “We gave that to some vendors and they did some tests. We had five vendors doing these tests for us and they were so excited about it - it was fun to see the different approaches from each of them.”
Ultimately, MPC would be awarded creation duties for Groot, with Framestore handling Rocket. Both facilities, however, produced each character for their respective shots, sharing models and textures but of course taking Groot or Rocket through their own respective pipelines (more on this below). Proof was also an important contributor to the performance of Rocket and Groot, even going so far as to build a real-time fur shader for Rocket and enabling special blend shapes to show Groot’s changes in size and scale.
A shooting methodology was devised that mostly utilized stand-in performances. For Groot, some exploration took place into mocap (including a performance from James Gunn himself), but it was deemed that this would not fit in with the style of shooting. The final approach made use of a mime (Krystian Godlewski) on set who would wear a blue body suit and wear a Groot ‘helmet’ featuring a printed mask that matched the character’s eventual eyeline.
For Rocket, several on-set approaches were employed. The director engaged his brother Sean Gunn to perform Rocket’s lines and also stand-in with the actors. A small statured actor also walked the scene with a picture of Rocket on her bodysuit to help with eyelines, while a stuffie raccoon was placed in the shots for lighting and positioning reference, aiding DOP Ben Davis in designing and positing lighting.
Each take, then, actually required multiple plates. These included a clean plate and ones that made use of the Groot and Rocket stand-ins. “The most important thing for us,” says Ceretti, “was to make sure all the acting would be believable and that the actors would be able to respond to another actor. Groot doesn’t have much to say - he says ‘I am Groot’ most of the time (ultimately voiced by Vin Diesel), but he has a lot of expression on his face and this determines what he means. Rocket has a lot of lines and jumps around, so it was important for James to have a real actor there to bounce around with the other actors. I think James was clever to get his brother to do that, first of all because he was really good at it, and the other actors loved it. They were afraid of talking to tennis balls - which they did end up doing but Sean would always be there next to the set.”
“That really created a huge base for everybody to work, for the actors to work on, for the camera operators to frame their shots and the editors to edit the scenes,” adds Ceretti. “For Rocket, for example, the editors would get the takes with all the actors in and Sean, and they would have two timelines, one with the reference and the other timeline with the empty version of it which we would use most of the time for the film. It was also great reference for the postvis people and it was a great reference for the animators and for Bradley Cooper and inspired himself for what was happening on set. And then the animators would see his recording sessions and use new things he’d done too.”
In crafting Groot, MPC’s main consideration was to maintain the character’s human qualities. “We were trying to understand how would we make him emote,” outlines MPC visual effects supervisor Nicolas Aithadi. “One of the things we realized early was that we didn’t want him to be too elastic and malleable. What makes a human face what it is, is the fact that it’s moving a lot. But because he’s made of wood we had to keep the notion that he’s made of a rigid metal.”
The studio recognized that Groot’s eyes would be key. “We spent a lot of time designing and building very complex eye dynamics,” says Aithadi. “We put a lot of detail into his textures and things that would be displaced in his irises - we really wanted to get shadows in there. And we worked a lot on trying to break the symmetry. When you look at humans what makes the eyes interesting is the imperfections - trying to make these two irises not aimed at the same place - trying to make them strange and look more human. I could watch a turntable of Groot for ages because he had this really piercing look and this wisdom in his face.”
Since Groot is tree-like, MPC decided to model him as individual branches; rigged individually. “You could move an arm and it would have a branch moving in his back or on his waist,” notes Aithadi. “It was our way of getting some muscle system into Groot. If it was a human character or soft flesh character we would have all this muscle sim moving around, but with Groot we made all his individual branches dynamically reacting to each other to create the notion that he was alive.”
Groot’s face, too, made use of individual pieces. “We decided to break up the face into all these little plates,” says Aithadi. “It’s individual geo modelled individually that looks like one object when it’s neutral, but you can see the plates sliding on top of each other. The moving plates system emphasized every expression he had.”
The creature was rendered in RenderMan. Textures for Groot came from a number of sources, including from a botanical garden visit in London. “We thought he might be one type of wood, but we realized that was kind of boring,” comments Aithadi. “And so we started to mix and match the type of wood. We went through hundreds of iterations for color and whether he had moss or lichen. We kept the moss mostly on his shoulders or head. We started making the feet and lower leg darker because he would pick up dirt, say, but then it looked like he had fuzzy boots!”
“Groot is actually a teenager, not an old tree,” adds Aithadi. “One of the things that makes wood wood is bark, but it looks like wrinkles on characters. We started with photographs of bark on his face - it looked cool but it made him look too old. When we started to take the bark away it started to look flat. So we had more rugged bark on the side of his face, but receding on his front.”
MPC carried out two animation studies for Groot (the studio’s anim supes were Greg Fisher and Gabriele Zucchelli). One study followed a humanistic look and one added in poses in between actions. This was the preferred style. “It was as if it was a couple of frames where Groot was tree-like static,” describes Aithadi. “It was giving him a weird type of animation - doing things a human can do but with a strangeness to it. Going from one animation to the other, it had a moment of stillness.”
Framestore matched MPC’s Groot for shots it was handling, by adapting its pipeline for the complicated character. One extra challenge was for the Kyln escape where Groot is shot at by several hover-bots and parts of his outer tree-structure are blown off. “We came up with this concept that he was going to grow a shield as an extension of his arm,” says Framestore visual effects supervisor Jonathan Fawkner. “But for the rest of the body we came up with this concept that he’d grow an extra layer of vines and twigs that gave a plausible answer to growing some sort of defence. He also had to grow twigs which we did via a Houdini plugin, an FX driven approach that could then be individually placed by an animator.”
Fleshing out the character of Rocket involved, like Groot, constant reference to the concept art, stand-in performances and voice characterization - all things that Framestore took into consideration in building the creature. “Everything came down from what we shot on set,” says Ceretti. “We had the actors there and the interaction was so natural there. There were, though, lots of little things the animators brought in. When Rocket talks about something, he’s always playing with something on the table. That’s something we found out from racoons - they are very tactile so when they grab something they really play around with it and work around - so these things made him very natural.”
Framestore’s brief for Rocket was that he would present as a ‘grizzled and cynical’ character, according to Fawkner. “That mood is not strictly true because there are moments in the film where you catch a glimpse of what’s really going on underneath this outward appearance of stand-offish grumpy character. It’s this injured and tortured soul. There’s a moment, for example, where he isn’t wearing any costume and you see his implants and biotech implants into his body.”
The studio received several pieces of concept art as part of the design exploration. “We went right back to a raccoon - we’d been given raccoon reference, we’d been to see a raccoon,” says Fawkner. “We did two versions of Rocket and in the end he got more bipedal and was more human sized in his proportions. We really dealt with him as a creature that could emote and talk, and that somehow seemed slightly easier once we had got his facial features sorted out. We had big shadows under his eyes which let his brows emote. All these things were gradually done to allow a face that would read more human.”
Of course, one of Rocket’s major challenges was his hair. For this, Framestore relied on its in-house hair system called fcHairFilters and its sim tool known as fDynamo. “This uses a series of filters that are built up into a network of different functions to give each hair its shape,” explains Framestore TD Rachel Williams. “As raccoon fur is made up from a layer of short fine hair and a layer of longer thicker hairs we were able to separate these out so that it was possible to only simulate the longer hairs. In doing so we were able to simulate the full hair count of the longer hairs instead of using a low density set of guide hairs to drive the rest of the groom. This resulted in much more accurate simulations. The fur was also separated into sections as the different costumes created natural split points. This meant we could easily remove parts of the fur which were not visible in shot. It also meant we had more hair sets to manage, altogether the three variants comprised of a total of 22 hair sets.”
The hair was rendered in Arnold with a Marschner shader based on the disneyISHair model. Williams says this is “an artist friendly, physics inspired hair shading system which uses importance sampling for hair scattering. For the markings we used multiple colour maps which were then mixed in different ways along the length of each hair. For the short fine hair we were able to achieve the speckled look along each hair which is present in real raccoon fur by swapping between the different maps in certain areas controlled by mix masks. The longer hairs had less colour changes along the length which gave the recognisable raccoon mask.”
Rocket wears a bounty-hunter costume and also prison garbs. Framestore CFX Supervisor Sylvain Degrotte oversaw the cloth sims that interacted with the fur simulations. To enable this, Rocket’s groom was split into the head, arms and tail that could be sim’d separately. The bounty hunter costume was more rigid, while the prison cloth was looser and had to slide and wrinkle much more - although it could be modeled from photogrammetry to get all the right wrinkles since the costume existed in real life. Framestore used its in-house software Jet to automate the simulation process.
In terms of animation, Framestore jumped on something Gunn had asked them to do. “James pushed us to not overdo it,” recalls Fawkner. “He asked us to carefully look at what the human actors were doing. He felt that animated characters can often look overdone for the sheer sake of seeing the face shapes that are available. He said actors don’t do 20 face shapes in one shot - they often just do one and hold it. And that we shouldn’t be afraid of being more minimal. James might have remembered something Sean did and want us to use that. Sometimes there would be something that they did in postvis even if Bradley or Sean didn’t do it. And then our own animators would also film themselves sometimes and use that as reference.”
Rocket carries with him a four-barreled gun. On set, production had 3D printed a version of the gun that Framestore then matched in CG. “I think they had a view that the 3D printed gun looked a bit perfect,” notes Fawkner, “so when they gave us the 3D asset we replicated that but they hadn’t loved the gun in the first place. So we beat up the gun a bit and MPC did a lot of shots where it extends and unfolds.”
MPC’s translation of Rocket, like Framestore’s adaptation of Groot, had to result in an indistinguishable version of the character. The main challenge for MPC was realizing Rocket’s fur in its Furtility system and rendering in RenderMan. “In Furtility,” explains Nicolas Aithadi, “we added the ability to load an Alembic file of Framestore’s work. We knew we’d have to tweak all the parameters in the fur to get the same model - not just the same groom. We had to keep control of thickness and layout of the hair.”
Peter Quill’s (Chris Pratt) adventures on Morag to steal an orb - seen early in the film - featured vast landscapes that were partial sets and then extensions by MPC, which also delivered shots for inside the temple where Quill confronts the Korath. “The planet was inspired by a place in Egypt called the White Desert,” notes Ceretti. “I actually went there to take some stills which were used as reference for building the sets back in London. Our approach with production designer Charlie Wood is that if we can build something, we should build it. We want people to be acting in a real environment as much as possible. We had to find the right balance between greenscreen and how much you can top up and extend.”
Designs for Morag continued to evolve, with MPC implementing a system of pointy and angular-looking ‘angry rocks’, according to Aithadi. “We also created these gigantic arch-like environments,” he says. “James wanted to have a contrast of a beautiful sky and a really gnarly - not ugly - but aggressive and contrasting ground. Mixed together it becomes beautiful.”
The sequence also includes the introduction to Quill’s ship, the Milano, a 777-sized craft that had to be lifted up by a geyser. “Our first reaction to that shot was ‘Oh my god!’,” recalls Aithadi, “but the effects guys did a great job of translating the size of the geyser.”
Quill then tries to sell the orb on the Nova Corps planet Xandar, where he encounters Gamora (Zoe Saldana), Rocket and Groot in a mall area. MPC was responsible for crafting visual effects for Xandar views and compositing live action mall photography into the city - which was actually in the shape of the Nova Corps logo.
“Xandar is based in many ways on Singapore,” says Ceretti. “There’s a place there called Gardens by the Bay which has that lush, kind of futuristic feel in terms of architecture and a very lush tropical feel. We did an extensive stills shoot and took some helicopter plates, although we didn’t end up using them in particular as our shots were slightly different. One of our main buildings in the city is actually a train station in Belgium that we went and scanned and photographed. We always tried to use stuff from the real world but modify it.”
MPC had to realize Xandar from aerial down to ground level views - while also creating cloud and sky geometry - and so proposed three levels of detail approaches to the city. “There was a LOD(a) city for close-ups and ground views,” explains Aithadi. “A LOD(b) city which would be for higher ups. Then a LOD(c) city that’s in lower res for 50,000 feet views which we used very time we have the aerial battle at the end of the film.”
DFX Supervisor Daniele Bigi and environment supervisors Marco Rolandi and Alexandru Popescu oversaw the CG work for Xandar. The (c) version was built first, with the studio relying mostly on V-Ray unless there were interactions with spaceships or explosions, in which case RenderMan was used. In addition to the Singapore reference, MPC also sent a VFX photographer to Shanghai and Dubai. “From all that reference we worked on our ‘Xandari’ architecture,” states Aithadi. “We wanted to have something that makes sense but at the same time it would have an edge and something that would make you believe it was extra-terrestrial and not just out of bounds.”
“We’d take pieces of the buildings and create another whole one using say windows or shapes or the facade of the building,” adds Aithadi. “We had 40 or 50 hero buildings designed and modeled. And we did more generic ones too. We ended up with hundreds of variations of buildings and populated the city that way. Then we had to create trees and vegetation. So we kept it grounded. We have trees that make visual sense but at the same time we were creating alien-type plants and flowers that could be added to the vegetation - like a palm tree but a spherical variation.”
For the ground views of Xandar, MPC took their (c) version and placed all the cameras that would be used for close-ups and surface perspectives, then only up-res’d buildings where necessary. The mall scene, in particular, involved extensions from live action filmed at Shepparton Studios of a walkway and courtyard set.
Crafting the Kyln
Transported to the Kyln, Quill, Rocket, Groot and Gamora team up with Drax (Dave Bautista) to escape the prison. Charlie Wood designed an elaborate set that required some extensions from Framestore, along with creature additions. “Lighting the Kyln was fascinating because there was no real precedent for how to light such a huge space,” says Jonathan Fawkner. “In the end we utilized these ‘sharpies’ lights they had on set. We were using Arnold and it has a volumetric lighting pass that’s relatively cheap to run. We got this nice effect by running moving lights over the surface of the prison which really picked up the geo, swinging the light through the lens occasionally.”
For the escape sequence, in particular, the studio orchestrated a fight between several hover-bots and Groot and Rocket. “We used the animation of the robots to derive where the destruction was happening,” explains Fawkner. “And now that we are rendering physically all the time, we still have to animate things off camera. If our animators stop animating the robot just because he goes off camera, his shadow will suddenly stop, or the bounce won’t be there.”
One dramatic shot shows Rocket perched on Groot’s shoulder firing his weapon - the plate for this was achieved by mounting a camera on a centrifuge rig counterweighted and had an engine that spun it around to capture the move.
As the robots hover about the set, Framestore implemented virtual spotlights on characters and walls. “The robots always had spotlights modeled into them, but at no point during the shoot had anyone shone any spotlights around,” says Fawkner. “I thought if we don’t put spotlights on these bots we’re really going to regret it - you’ve got all this lovely backlighting, lens flares, volumetrics - it was too good an opportunity to pass up. I’m really pleased with it as it elevates the drama. We used a lot of 2D elements too. My garden got pillaged for twigs and sawdust and trees. We came into Framestore’s stage and we shot a bunch of elements with compressed air.”
In the end, Rocket disables the anti-gravity system in the Kyln and pilots the prison watchtower to safety - an all CG shot by Framestore. “That was shot on a gimbal with all the actors, but we also had them as 3D assets so ended up doing that entirely CG,” notes Fawkner.
Ronan (Lee Pace) visits Thanos in the Dark World where the villain appears on a hovering throne amongst a rocky outcrop surrounded by nebulas and asteroid fields. Luma Pictures devised a new facial animation system to re-create performer Josh Brolin as a fully CG Thanos. “He had to be the bad ass,” recounts Luma visual effects supervisor Vincent Cirelli, “and we had to give him the performance and the weight that that deserved.”
Luma received an initial facial scan of Brolin and quickly determined that the actor’s strong facial features were a suitable fit for the emphasized jaw and facial lines of Thanos. The studio also received an initial concept sculpt for the character to work from. “Loic Zimmermann our concept designer took the most prevalent features of Josh that we thought would stand out the most and put them into who the character is underneath,” says Cirelli. “He began blending those elements. We’ve taken Josh’s eyes, some of his cheek, how his muscles move when he talks and blended that into his caricature. Thanos has this incredibly large jaw and deep grooves that run throughout his face which needed to be carefully planned out with the movement of his face.”
Brolin was captured using the Mova system, with Luma exploring two paths to take that performance and deliver their CG character. “First,” says Cirelli, “we looked at a direct drive path where Josh’s performance directly drives a mesh. The problem with that is that Thanos’ mesh is so different in the forms than human anatomy. An alternative path resulted in our new software called Face2Face that goes in and takes an entire performance and dissects all the muscles and shapes that are triggering that multiple poses over the course of a performance.”
Devised by Paul Molodowitch, Face2Face looks at what poses need to be followed, with the baseline being the traditional FACS poses. “It goes through and determines at any time temporally how many of those FACS poses are being blended, and then the blending threshold,” explains Cirelli. “Once we dissect what’s being used for each motion per frame, it then re-targets that motion using our library that mimics the FACS library. Our library is made up of Thanos faces and expressions and FACS poses.”
Watch the end of this Marvel recap video for a small glimpse of Luma's Thanos.
The core of Face2Face exists inside of Maya and was created to be as automated as possible. “It’s really taking that Mova information and figuring out based on our library what percentage of each pose goes into it,” states Cirelli. “And then what it does is allow us to automatically apply it to any sort of creature or animal. The tricky part was working out whether we should do it as more of a direct drive route. But when we tried to apply a direct drive to Thanos, we ended up finding that the muscles you expect to find on Thanos are in a much different location on Thanos. They’re far enough away that a direct system would just fold on itself.”
The animation out of Face2Face got the studio about 75% of the way there, notes Cirelli. “We then had additional tools in simulation that add subtle movement across the surface, then there’s blood scattering, compression, extensions mattes to help push displacement up down for wrinkles and skin. Then there’s a final displacement on top of that.”
Thanos’ skin was the next challenge. Luma referenced texture shots of Brolin and then hand-painted CG textures in MARI, which was also used for Thanos’ distinctive metal armor. The studio relied on Arnold for rendering the armor, environment and skin. “Purple is just damn hard to pull off!,” says Cirelli, referring to Thanos’ skin color. “The value was dark. You don’t have quite the luminance you expect to have to apply light transmission. We took a bunch of cross-polarzied photography of people and skewed their skin as a purple shade, just to test out where we needed to go.”
Knowhere: somewhere different
Quill and his new friends hope to sell the orb and head to Knowhere, a criminal space outpost built in the giant severed-head of a celestial. “Conceptually,” explains Ceretti, “it was a big skull in space where there’s this mining operation taking place, and there’s a city in there. Charlie Wood hired Kevin Jenkins from Framestore to design the look, and there was a lot of referencing of favelas in Brazil and mining operations. We got an initial 3D model from the art department at Framestore, and from that we took that into our previs team and they started fleshing out stuff and laying out scenes including the mining pod chase.”
Knowhere also perhaps evidences most clearly the role color played in Guardians. “James wanted a very vibrant movie,” says Ceretti. “He thought many films lately have been gritty and dark, almost monochromatic, that feeling of bleach by-pass. What he wanted to convey as an absolute opposite was that space is vibrant with many colors, lots of different textures and in Knowhere - it has different color temperatures in it. Red and yellow are very important. Yellow color is used in the movie at moments where there is a very important shift in the movie or something important happening to the Guardians - he calls it the baptism color.”
Views of the area around Knowhere included clouds of nebulas and a gaseous world. “Static shots had matte painted elements,” comments Framestore visual effects supervisor Kyle McCulloch, who shared duties with Jonathan Fawkner and was also Framestore’s on-set supe. “But action based shots required the effects team to sculpt nebulas that we would dress and light and render to get a sense of the emotion of atmosphere in space.”
For inside Knowhere, Framestore built 250 base pieces and shapes in its layout software called fShambles to construct an extensible system that would make up Knowhere. “Then our environment team spent eight months literally building the entire world,” says McCulloch. “It let us fly cameras in and around and up to based on the changing edit and the needs of the edit.”
Framestore’s artists placed tens of thousands of individual ‘local’ lights to light up streets and windows and alleys and different geo in Knowhere. “Then another group were doing mid-sized lights, big spotlights with lots of colors,” says McCulloch. “Then there was hero lighting. So there was a lot of back and forth between the teams doing that to make it as vibrant as possible.”
“We then built a workflow that instanced geometry and used that in production with Arnold and shading methods,” adds McCulloch. “There might be 90-100,000 instances in frame at one time. Being able to render that was a huge win. Our bi-direction shading model was crucial - one shot had almost 30,000 individual lights in it that the camera could see at any one time. Our previous shading model from Gravity was not even as capable as that!” Framestore also used its texture projection software fStop to help create Knowhere imagery.
After an effects sequence inside The Collector’s (Benicio Del Toro) lab - involving explosions and black fire from the Infinity Stone - the characters end up commandeering some mining pods and are pursued around Knowhere. Proof previs’d the shots for the dynamic chase with its unique toon shader look. “The space pods go at a very fast rate,” notes Proof previsualization supervisor Earl Hibbert. “We worked with James to design a path of action through the Knowhere set, all the way through the set so we were never seeing the same part of the set twice. There was very specific moments and gags to design that action and work out where we going to travel through Knowhere. James never wanted the audience to get confused about where they were in the location.”
For final animation of scenes in Knowhere, Framestore loaded and unloaded specific quadrants that were near the ship, ie. near the camera. “We also have a QC pipeline process in place,” says McCulloch, “that allows animation to work on extremely low-res or localized versions of the world, and then they can kick off a relatively light weight render quickly to make sure everyone is working.”
The actors were filmed on gimbal ship sets. “We did replace most of the cockpit and the ship,” acknowledges McCulloch, “but it made shooting a lot less stressful because we knew what the beats of the action were going to be. Using our Conform experience on Gravity - taking filmed faces and putting them into CG shots - we did a similar thing with the actors on the gimbal and needed to put them into spaceships, so having that already fleshed out from Gravity was a huge thing.”
Framestore utilized its new generation of fire and smoke simulation approaches - tools known as Flush and fmote - to do explosions on a massive scale. “There are a couple of shots where the ships crash into each other,” describes McCulloch, “and the director wanted to slow down to about 600 frames per second, so doing big big fireballs at that speed over long shots - we’re also working really hard with the shading team to render these in a reasonable amount of time.”
One shot features Rocket driving his pod through another ship and he emerges from the flames. “We did that with a series of massive sims and mixed and matched them to get the best result,” explains McCulloch.
On Knowhere, the team visits The Collector who shows them the secrets of the orb, actually an Infinity Stone. Method Studios worked on shots that showed the orb opening up to reveal its powers. “They wanted to tell the story of these arms spinning around like a Rubik’s Cube,” says Method Studios visual effects supervisor Greg Steele. “It was really a high tech 360 degree Rubik’s Cube - it has this interlocking mechanism. Each time something is unlocked there is something inside of that. So a little bit of light would start bleeding out of the cracks.”
“They shot things on set with a physical placeholder,” adds Steele. “We changed the top of the table to make it more of a computer screen. We added little threads of particle energy. Then when it opens you see the reveal, a combination of particles in Houdini and rendered in V-Ray. It then shoots up a dome around them which is a net of little circular screens around them. On the screens he’s telling the story of the Infinity Stones and the birth of the universe, so on the screens we created material like the big bang - a huge 8K element done in Houdini with a ton of different layers we could adjust.”
The final battle
Ronan attacks Xandar in the Dark Aster but is met by Yondu's fleet, the Nova Corps and Quill's group. Proof delivered extensive previs for the sequence (with The Third Floor contributing previs for the net sequence). MPC tackled the complicated shots with a new approach to crowd and effects simulation.
Even though it was a high action endeavor, Gunn requested of the Proof team that the humor remain on screen. “We had these big action set pieces,” says Earl Hibbert, “but it was important that the characters come through in the action. So their decision making was very particular to their character.”
With so much action occurring around the Dark Aster - a 4km wide craft - and with so many kinds of spaceships, MPC launched a ‘training ground’ to devise how each ship would fly. To choreograph the action, MPC combined its proprietary crowd system ALICE with Softimage’s ICE framework. “We had the ships flying, doing the same action, banking in and slowing down, accelerating and boosting away,” explains Aithadi. “Every single ship had their own personality. The Ravagers, for example, were like muscle cars - powerful but vibrate-y. The star blasters from Nova Corps were more sleek and high tech. We looked at very sleek cars like lamborghinis for how clean and nice they were.”
“The necrocraft design was strange, too,” says Aithadi. “It’s a bullet with two wings that don’t really move. I saw a video of slow motion flies. The flies were doing some really weird movements which we liked. They had a weird weightlessness and don’t really obey the laws of physics. We added some helicopter to the animation to bring it back into a more acceptable movement, something you would recognize as normal.”
In building the ships seen in the battle - which were dense models - MPC established a streamlined approach to multi-resolution assets so that only the level of detail required would need to be rendered (done in RenderMan). For that the studio relied on up-front geometry and skeleton caching. They also used animation rigs that would bind to different ship models. And MPC devised a system that dealt with level of detail for animation so that only information that was visually relevant for each shot needed to be lit and rendered.
Explosions and effects were also incorporated into the crowd system. “There were so many explosions that it couldn’t be dealt with in effects only, as that wasn’t practical,” says Aithadi. “We had to make our crowd system deal with explosions. The effects team created a library of explosions - hundreds of individual explosions to sim. The crowd sim team were populating the shots with hundreds of explosions in low res. We could move them around and make sure we didn’t have patterns. The cache would go to effects and effects would attach the explosions.”
In a sequence added relatively late in production, the Nova Corps use their star blasters to connect and form a net over the Dark Aster in the hope of slowing its progress. The Third Floor previs’d and postvis’d the scene. “James Gunn drew thumbnails of the shots he wanted in the sequence and described the way he wanted the shield to look,” says Third Floor previs supervisor James Baker. “We did a bit of R&D on the look with VFX supervisor Stephane Ceretti and settled on one that James liked. Then one of our previs artists, Pat Gehlen, rigged up an energy net that could be conformed to the shape of the ship. Once the live action was shot, we did postvis on this sequence.”
MPC CG supervisor Stephane Paris then oversaw final net shots which ultimately required thousands of star blasters to be seen on screen. “We had to make a mathematical shape that would deform with the Dark Aster,” relays Aithadi. “Crowd sim wasn’t the solution - we created a grid plane and each point of the plane was a star blaster - and it was cloth simulated to wrap around the dark aster. The crowd people would attach a star blaster to each point. We would create the neck based on that.”
MPC’s work for the final section of the action on Xandar extended to the crash of the Dark Aster, Groot’s heroic act for his friends, and a scene involving Ronan and black fire from the Infinity Stone.
During the battle, shots of the Nova Corps command center feature a holographic display of the Dark Aster and attacking ships - shots created by Method Studios. “Originally it started out with more traditional holographic looks,” says Method visual effects supervisor Greg Steele, who shared duties with Stéphane Nazé. “We were able to get models from MPC of the Dark Aster and some of the ships and we started putting together a rough approximation of the city.”
“In the lookdev,” adds Steele, “the director went for a more photorealistic look - less of a light based thing and more of a volume thing that you could reach out and touch. From there we added city at the bottom. With the city there, the ships would be so small at this scale, so he had do things where the ships would zoom up or a squadron of ships would zoom up while keeping the ships in scale. MPC gave us all the models of the city and walkways and things and we did these as V-Ray proxies at rendertime.”
Also during the battle, Drax, Groot and Quill fight Koranth and his henchmen inside the Dark Aster. Imageworks worked with MPC to contribute to the Aster shots, including one of it re-entering the atmosphere and others for the fight which had been filmed mostly against greenscreen. “We had to build the ship interior,” explains Imageworks visual effects supervisor Pete Travers. “It had to be an engine room but it’s not built by humans so it was meant to look old and made out of material that was half out of stone and steel. We added in atmospherics into it as well. We had these turbines with weird spinning blades, almost like harvest combines that were just to increase the danger level of the environment.”
“On set,” notes Travers, “they were throwing each other against big greenscreen bucks and walls. So on our CG set we had to build walls at a certain angle and we simulated concrete-like breakup as they hit them. Where they shot the greenscreen they had a practical floor in some shots. So probably the biggest trick with that was blending the real floor with the CG floor.”
In the end, Guardians of the Galaxy featured VFX that covered around 90% of the film. For overall supervisor Stephane Ceretti, it was a film that had him and his team working hard with vendors around the world, but always enjoying the entire process. "We have been laughing so hard on this movie," he says. "It’s a crazy movie but at the same time that it’s hard, it's rewarding to see it all on screen."
All images and clips copyright 2014 Marvel Studios/Walt Disney Pictures.
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