Vincent Cirelli (vfx supervisor), John Cassella (senior fx TD), Richard Sutherland (CG supervisor), Raphael Pimentel (animation supervisor) and Steve Griffith (vfx producer) give us their insights on Venice, Calif.-based Luma’s mythical effects work on Percy Jackson and the Olympians: The Lightning Thief. The team contributed nearly 90 shots for the film and tackled insane challenges like Medusa’s writhing head of snakes and Poseidon’s watery transformation.
Snakes on the Brain
Under the guidance of the production’s vfx supervisor Kevin Mack and their own exec visual effects supervisor Payam Shohadal and vfx supervisor Vincent Cirelli, the crew at Luma turned the lovely Uma Thurman into a gorgon with a mane of over 70 snakes, each with unique looks and personalities, not to mention rigged 3D scales that flare and flatten to compliment the snake’s body movements.
Percy Jackson and the Olympians: The Lightning Thief
Animag: How long was dev process for Medusa’s snake effects? Did you go through many iterations before reaching a solution?
Cirelli: We received fantastic concept art from production, but needed to conceive our own once we started blocking out the model. Our in-house concept artist, Loic Zimmerman, worked through many different iterations of medusa. This helped us define what kind of snakes we would ultimately use, their sizes and length, where and how they lay on Uma [Thurman]. This was beneficial, in that we had a design that could work within a 3D space, and within the boundaries of Uma’s actual head dimensions, before we even got into serious modeling/rigging.
Animag: Which programs were used to achieve the snake body dynamics and 3D scale effects?
Cassella: Medusa’s snakes were rigged for traditional animation, and then a custom dynamics simulation system was built on top of that. Leveraging Maya’s nParticle system and its ability to calculate particle collisions, a rig was built that turned every snake into a particle chain. This allowed us to implement artist friendly controls for such things as wandering, target seeking, goals and stiffness to achieve and find defined hero poses during initial dynamic simulation to give the snakes weight and inertial motion.
Percy Jackson and the Olympians: The Lightning Thief
The animation rig was driven directly from the particle simulation through a custom plug-in, which moved the snakes and set keys on the same controls the animators would later work with. This initial simulation was baked as a base layer, and then character animators took over to give the snakes their personality.
Familiar Waters
Luma’s superstar fluid dynamics team was responsible for creating a watery transformation worthy of a Greek god when Poseidon (Kevin McKidd) emerges in all his glory from the sea and then morphs to a normal human size, stripping away his volume in torrents of water. With Real Flow and a custom dynamics rig they achieved this look, not to mention plenty of surrounding fluid simulations to sell the shot.
Percy Jackson and the Olympians: The Lightning Thief
Animag: How much experimentation was required to get the Poseidon transformation down?
Sutherland: Unlike an explosion or a helicopter, the Poseidon transformation effect was not something that we could find definitive reference for, so there was quite a bit of experimentation. We knew the basic idea behind the transformation, Poseidon in god form is over 60 feet tall and by shedding water he ends up as a normal size human. Since it was the first introduction to Poseidon’s and, by extension, Percy’s, main power, it was important to show both power and control. To sell this transformation we needed to make sure it was clear where this huge volume of water went. Some of our initial designs had the water dropping onto the pier and flowing back to sea, but the director felt it did not demonstrate the complete control over water that Poseidon has. Once we got the idea that Poseidon’s control of water was a sort of control over gravity our R&D became more focused and we honed in on the idea of sections of his form peeling off and levitating back to the ocean. This made the loss of volume obvious, while demonstrating the total control over water that Poseidon has.
Animag: What inspired the breakthrough to create the end result?
Sutherland: After we had decided on the basic idea behind the transform, the major breakthrough was involving one of our animators in the blocking process. I set up a rig that the animator could use to time out which areas would peel off and how long the negative space stayed before the form flowed back together. His understanding of timing, action and composition provided a solid foundation for the transformation sequence. Using spheres allowed us to test out different timing and spacing patterns much more quickly than full simulations. Once we found something that read well and was dynamic enough we could do low-res simulations overnight to see how it all played out. This methodology allowed us to get to the end result with a minimum of time-consuming full resolution simulations.
Percy Jackson and the Olympians: The Lightning Thief
The VFX 411:
Animag: Of all the shots, which scene or effect proved the most challenging to crack? Which did the crew have the most fun with?
Pimentel: Undoubtedly our biggest, but most enjoyable challenge was animating Medusa. Playing off of Uma’s performance was a task in itself, many snakes needed to be hand animated. We knew that the animation workload would be immense but felt it would need an artist’s touch and that a procedural method would only get us so far. We developed powerful animation tools to help us work through the fact that in many shots, we needed to animate up to seventy snakes at a time to create little stories within the sequence. Using Maya’s animation layers, we combined multiple passes to create the final animation you see on screen.
Animag: Are there examples from Luma’s past work that helped the team solve this film’s puzzles?
Griffith: We have built an elaborate pipeline for creating natural fx like water over the years. Many of the tools that we have created deal with the large data sets and ways in which we can trim the fat, ultimately allowing us to render with more detail, faster. In addition to the barrage of custom tools, we have also developed techniques for creating realistic white water, for large-scale simulations. The end result is a system of tools that layer nicely together and allow us to partition out various aspects of the simulation for isolated refinement, and then bring it all back together for final render, without losing interaction between elements.
Animag: How do the complexities of the Percy Jackson shots compare to other work Luma has tackled?
Cirelli: Percy was a challenging show, just like any other large blockbusters that we work on, where the effects and character work is extensive. But over the years we’ve defined a very organized, and artist friendly pipeline that allows us to turn around iterations very quickly. Ultimately, like most things, the more iterations you have, the better the end result.
Are there any funny studio anecdotes from this production? Did everyone make it through unscathed?
Cirelli: We received the props from production, and I think a couple of our guys were walking around as Poseidon during delivery!
Sutherland: We have a great team, and I hope nobody was scarred permanently. I know that just about everyone had dreams about snakes at one point or another in the process. It’s pretty certain that none of us will ever look at a snake the same way again!
Animag: Which is your personal favorite moment from Luma’s work in the film?
Cirelli: My favorite moment is a shot during the Medusa sequence where the snakes are interacting with her, fighting amongst themselves, and caressing Percy all at the same time. Throughout the Medusa sequence, you’ll find lots of little stories happening in the animation that you might miss the first time through… Some of them are comical, if you look closely enough.
Percy Jackson and the Olympians: The Lightning Thief is currently playing in theaters nationwide. Learn more about Luma Pictures at:
