Handling the responsibility and pressure of producing an awesome third act is something that New Zealand's Weta Digital thrives upon, most recently demonstrated by their work on the Final Battle in Marvel’s Guardians of the Galaxy Vol. 2.

The epic battle takes place deep within the center of Ego the Living Planet. Much of the third act’s psychedelic imagery was influenced by the fractal work of mathematician Benoit Mandelbrot. “Working out what the environment was going to look like took a lot of development and mathematics,” states Weta Digital animation supervisor Dave Clayton. “Initially, we weren’t expecting to make Ego the Living Planet move as much as we ended up doing. So, as animators, we needed to visualize the higher resolution layout of the set in our scene files, select different parts, move them around, and sometimes mock-up some destruction or growth because Ego the Living Planet is always evolving. Our effects team was under the pump to get this movie done so we selected key shots, did either general transforms of the set pieces or mocked up some growth, and got them approved in animation form. Our effects team was able to use that as a roadmap to get everybody on the same page.”

“Our lighting team did an amazing job guiding the eye and using actual glowing light to cascade up the walls or illuminate Ego’s facial forms on the walls of the cavern,” Clayton notes. “For us in animation, we tried to pick out cool compositional elements and stage shots as best as we could. But then those shots were transformed into something completely fresh and exciting once the lighters got hold of them.”

Clayton’s team drew inspiration for Ego’s transformation process from unusual sources. Says Clayton, “There’s a scene, which is more animation-centric, where Ego transforms into his human form. He builds up from a skeleton to muscles, organs, and then eventually skin, hair and eyeballs. It was fun playing with the 1980s Guardians of the Galaxy aesthetic. Having his hair grow out in crazy ways while his eyeballs were still exposed, it looked like a Heavy Metal album cover -- having his skeletal face delivering dialogue was really cool.”

“Our effects team had been conducting motion studies and formation tests for months leading up to when those transformation shots were in production,” Clayton explains. “They were developing the technology to make the growth look organic and real. We plotted out the timing of when each of the body parts would reveal and how they would reveal because it was staggered over eight to 10 shots.” Blue light washed over the body of Ego as he transforms. “We weren’t privy to what music was going to be used there. But when Peter Quill [Chris Pratt] fights back against Ego and harnesses his own powers, editorial had Fleetwood Mac playing in the background on the previs and postvis. That was cool to hear and gave us a sense of the timing they were after.”

Weta worked from numerous live-action plates filled with stunts shot for the Final Battle. “There were times when the characters would jump and you could tell they were suspend by wires,” remarks Clayton. “In those cases, we would go to our digital doubles, do some motion-capture, augment that with key frame polishing, get it to fit within the shot and observe continuity.” Destroying a planet is never a simple task to achieve especially when you’re trying to make it appear unique and believable. “We needed to implode Ego across a handful of shots. But of course, in real life, I imagine that when a planet is destroyed it would take years,” Clayton notes. “That was a big challenge. The way we got around that was having these spiralling explosions that would implode and suck in on themselves. The other thing that the effects team used quite well was a ripple effect of cascading explosions. You got that feeling of escalation. It looked cool visually.”

In the midst of the Final Battle, Rocket displays an emotional side quite different from his usual sarcastic persona. Says Clayton, “He shows vulnerability and sadness as he bonds with Yondu. These are new emotions for Rocket to experience. Marvel Studios VFX supervisor Chris Townsend was great at sending us the most successful shots from other vendors. We could study those, hit the ground running with Rocket, and get him up to speed with the other vendors.” Creating the believable illusion of a talking Racoon, voiced by Bradley Cooper, involved visualizing a host of physical nuances. “What we discovered was as you’re talking, your body moves, your chest surges in certain ways, and your head gestures in correlation to the timing of each syllable. That sort of stuff is important to make a CG character feel like they’re actually delivering those lines and living that moment,” Clayton describes.

Another key component for Rocket was his fur. “We used some wind simulation techniques, where we put a lot of dirt and debris into Rocket’s fur, particularly in the third act after he had been battling Ego,” remarks Clayton. “In terms of the facial animation, once we saw the result rendered, it looked different with the fur. Although we have experience with Caesar [in the Planet of the Apes franchise] doing amazing lip sync, his fur is on the periphery of his face, whereas Rocket has fur all over his face. We had to do a bit of trial and error on how to display that fur on our puppet and how to get our puppet correlating with the final result.”

Another key segment of Weta’s work on the film was the 10-inch high sentient sapling known as Baby Groot, who had to look like an alien species made out of wood rather than a plastic anthropomorphic character. According to Clayton, “If we were to give him too much detail in his facial shapes and in the performance of his lips, he would look wrong. We tried to keep it simple because he is a baby version of himself. An example would be the shot after they come out of a space jump and Baby Groot vomits. Being animators, we tried to get the most out of that shot and put in a lot of heaving as he puked, various shape changes and different expressions from happy to disgusted. But director James Gunn said, ‘You’ve gone way too far. I want to keep this simple.’ When a toddler vomits often they don’t even know what’s happening. That simple methodology worked well on Baby Groot.”

Baby Groot has a tendency to be easily distracted and lost in his own world. “We wanted to keep him engaged with what was happening, especially when he’s sitting on Rocket’s shoulder or very present in a shot,” explains Clayton. “But, we didn’t want to give the impression that he knows everything that is happening. We wanted him looking around the room or minding his own business. That pays off in my favourite shot that we worked on where Rocket says, ‘Welcome to the freakin’ Guardians of the Galaxy.’ We tried a few different options with Baby Groot in that shot. First, we made him fully present like he was nodding, shaking his head in agreement with Rocket and really there. Interestingly, that performance ended up in the trailer but in the movie version of the scene he was toned back. Baby Groot looks at Yondu in a knowing-wise-beyond-his-years kind of way. He didn’t nod or shake his head or do any gestures. Baby Groot is just there.”

Destroying the spaceship of the Ravagers known as the Eclector was the first series of shots Weta worked on. “We did cascading explosions,” states Clayton. “I animated a bunch of those shots myself and it was cool. When animating a spaceship, you animate with two or three keyframes within the shot. It’s all about the camera design and speed, the timing of those explosions, playing those events slow enough to get a feeling of mass, speed and scale as well as keeping the story moving along.” Plausible camera movements and position are central in the design and composition of CG scenes. “Everyone wants cameras to be legitimate, where the action looks like it could have actually been shot. Everyone is thinking in terms of the lenses, how that camera would be mounted, and how much camera shake is realistic. You just don’t want to snap the audience out of the moment. That’s a fail.”

“We have a nice camera push in on Rocket’s face as he says the line, ‘Welcome to the freakin’ Guardians of the Galaxy,’” Clayton notes. “It’s a high point in the movie. It’s a great shot of Rocket and Baby Groot. They look amazing with the wind and dust blowing around and all of the dirt in Rocket’s fur. It’s a nice moment between Rocket and Yondu. I enjoyed working on that shot with my lead animator, Rocky [William Vanoost].” Clayton concludes, “The biggest challenge was the variety in the work that we produced. Every shot or series of shots had a different visual challenge. There was a lot of custom visual effects work that as animators, we wanted to help to drive. We did about 600 shots that were unique and a lot of effort was put into every single one of them.”