“Medusa and Poseidon are absolutely stunning and represent some of the hardest work on the project. Luma’s passionate artistry and technological brilliance combined with the easy manner and can-do attitude you maintained throughout the project have impressed me beyond words.” ~Kevin Mack, Visual Effects Supervisor, Percy Jackson and The Olympians: The Lightning Thief
Percy Jackson & The Olympians: The Lightning Thief is the latest in a long list of imaginative films by director Chris Columbus. In order to create the fantastic menagerie of gods, demigods and monsters, Columbus turned to acclaimed Visual Effects Supervisor Kevin Mack, who is well versed at bringing this kind of tale to life for big screen audiences. The project was quite an undertaking and when it came time to parcel out the huge number of CG creatures and effects needed to make this film a reality, Columbus and Mack partnered up with Luma Pictures to tackle two of the most challenging characters in the Film, Medusa (played by Uma Thurman) and Poseidon, a.k.a. “One of the Big Three,” (played by Kevin McKidd).
In bringing Medusa to life, the seasoned crew at Luma, helmed by Executive Visual Effect Supervisor Payam Shohadai and navigated by Visual Effects Supervisor, Vincent Cirelli set about to conquer the daunting task of turning the lovely Uma Thurman into the beguiling monster that turns flesh to stone with a mere glance. “Turning Uma’s hair into a roiling mass of over 70 snakes is no job for the squeamish,” recounts Vince Cirelli. “ In one major shot, we are close up for over 700 frames of individually animated CG snakes.” To make Uma’s character really slither on screen, the team started off by creating a dynamics layer over top of the animation rig in order to ensure that whatever the performance called for, the snakes could move freely without running into each other. “The challenge was to not only seamlessly integrate these snakes into Uma Thurman’s hair line, but also to give them each a personality,” comments Animation Supervisor Raphael Pimentel. “It was like directing 70 + extras on set, each snake reacted to the environment, the actors in the shot and with each other.” Luma designed the effect so that the snakes were Medusa’s all seeing eyes, reacting to events before she knew about them.
The result is a seamless performance of actor and digital prosthetic that really sells the story of the Gorgon priestess. “One of the great things about working with really well trained actors is that even if they are acting against a green screen or simply imagining their CG add ons, they can still bring the feeling home to the audience,” notes VFX Producer Steve Griffith. There were several shots in which the actress is in a battle with the heroes of the story and her performance is so dynamic that the team at Luma had to create equally dynamic animation to match. “Uma Thurman provided us with a lot of material to work with; she really visualized the motion of her CG character and added the perfect amount of weight to her performance to bring it to life,” adds Griffith.
In order to bridge the gap between fantasy and reality, they had to make snakes look like, well… snakes and Luma is no stranger to coming up with creative solutions in this department. Each of the 70 + snakes on Medusa’s head has a unique patterning and scale design and the larger snakes have an elaborate system of 3D scales that really sell the reptile look. “We devised a rig that allowed us to add 3D scales that could be matched to the performance by the animators,” remarks CG Supervisor Richard Sutherland. “The result is not just a bunch of bending tubes, but a scaly outer shell that fans out naturally with each wriggle”.
What would an on screen incarnation of Medusa would be without the classic “flesh to stone” effect that she is so (in)famous for. “To create this signature effect Medusa has on her victims, we wanted to stay away from the standard animated texture reveal of stone underneath the skin and come up with something unique for the audience,” Vince Cirelli explains. “What Chris and Kevin wanted was something more like a lakebed drying out in a time-lapse sequence, taking place in real time”. The result is a perfectly matched digital double whose surface is composed of tiny textured geometry flakes. “The skin transformation is driven by hundreds of thousands of particles, created in Houdini and animated over the surface of the woman’s body. As the particles pour out from the emitters, instanced geometry flakes turn outwards to create a unified surface,” adds Sutherland. The end result is a dynamically evolving effect where the actors’ life force seems to dry out right before our eyes.
For the main character of Poseidon, Luma brought out its superstar fluid dynamics team to handle the task of transforming the God of the Sea to and from human form. Using Real-Flow and customized dynamics rigs, Luma was able to dissolve the actors’ body into and out of a rushing torrent of water. To make it even more challenging Poseidon enters our world as a giant of mythical proportions and has to shave off some water weight to come down to human size. Justin Johnson, Luma’s Digital Effects Supervisor on the project, states “We had to really pay atteion to the volume of water contained in his different sizes so that the proportion of water leaving his body made sense when bringing him down to human scale.” The team also had to create the effect of Poseidon emerging from his underwater kingdom. For this shot, the actor was shot dry moving against a green screen and the artists at Luma had to come up with a creative solution to achieve that “wet look”. “We created really precise match move geometry to track to the actors face, then we used this to run Real flow simulations to create water sheeting off his skin,” Cirelli explains. Poseidon also emerges from the sea, god-sized, so they had to create surrounding fluid simulations in order to sell the effect of such a large scale object emerging from the sea. “The effect is more like a submarine emerging from a dive rather than a swimmer in a pool,” adds Johnson.
No tale of heroes and heroines would be complete without a story of teamwork and that was the spirit of the show throughout the whole process. “Chris and Kevin really knew what direction they wanted to take the audience and kept the communication going with almost daily feedback,” comments Griffith. “They really made us feel like we were all part of a team working towards the same goals.” The feeling was mutual, as Visual Effects Producer Denise Davis points out, “We had a truly great experience with the Luma team. The work was extremely difficult, yet your team made it seem so easy and rolled with the punches (with enthusiasm) every step of the way”