'Wrath of the Titans': Giving Strength to Kronos

Method Studios VFX supervisor Olivier Dumont walks us through the complex building of Kronos and the Underworld for the Clash of the Titans sequel.

All images © 2012 Warner Bros. Pictures.

Watch a great clip of Method's Kronos vfx sequence.

From the outset, director Jonathan Liebesman wanted a more grounded and less "magical" approach to Wrath of the Titans. This naturally extended to the VFX provided by Method Studios, with the work being divided between the London and LA facilities, under the supervision of Olivier Dumont. The onset VFX supervisor, meanwhile, was Nick Davis.

The main sequence for Method in LA involved the awakening of the monstrous Kronos, father of Zeus (played by Liam Neeson). This fully CG rock giant is brought to life with glowing lava and causes the cataclysmic destruction of the Underworld. During pre-production, Method in London created concept images for the production's art department, as well as the VFX in the establishment of the Underworld sequence.

The Kronos sequence included 114 shots featuring the CG creature in a fully CG environment consisting of more than 7,000 pieces. The action takes place in a huge collapsing chamber, with Perseus (Sam Worthington) and Andromeda (Rosamund Pike) freeing Zeus as Kronos awakens. Digital doubles of leading actors were created and composited into scenes along with fire, smoke, explosions and flowing lava.  For the Underworld establishment sequence, Method London's challenge was to get across the massive scale of the CG environment, which included detailed matte paintings and the creation of a stone pillar tower that Zeus is later bound to. In this VFX intensive scene, Zeus is drained of his powers as fiery lava bleeds from his arms and flows into the surrounding rocks to give Kronos strength. 

"The big challenge was the destruction of the mountains -- what we call the pyroclastics -- and also all the lava and the animation of Kronos itself," Dumont explains. "The way we were briefed at the beginning was that Kronos wasn't supposed to move that much, and so we built our animation for that. But during post- production, they altered the plan and the director wanted Kronos more mobile and to be seen getting free. This was in order to add more dramatic tension. And so we had to make a major adjustment."

The sequence is split into two primary locations pertaining to the tower known as Tartarus: outside where Kronos is bound and inside where his awakening is revealed. The outside was comprised mainly of 3D matte paintings for the set extensions and Tartarus reveal. The inside required full modeling and texturing. There were three stages for Kronos, who is attached to the mountains: sleeping, awakening (yet still static) and moving with massive destruction occurring all around him. (MPC was responsible for the post-awakening of Kronos for his climactic battle outside.) The animation was done in Houdini (with augmentation by Nuke). Everything was built and textured as blocks; and then merged to simplify the model and to render. ZBrush was used for modeling and Mari for texturing. MPC handed over a low-res model of the base along with the main design of Kronos when he's on the surface. But Method was able to adjust the look of Kronos to fit their needs.

Pyroclastic effects were used when Kronos breaks free and they used lots of reference from Hawaiian volcanoes. Large pieces break into smaller ones and they eventually become fluid.

The lava, of course, was an integral part. There were not only different setups but also different scales, ranging from a wound on Zeus' arm to the wider flow linking the main island to Kronos. The setups were created in Houdini based on a basic procedure, but the individual looks and speeds were determined for each scale. The approach was to use minimal simulation to drive the art direction (textured sculpts) in keeping with the more grounded vision of the director.

There were three phases to the setups and required various tools: one tool fractured the mountain based on a map and created the volumes inside; the initial animation was done by hand and then this was used to art direct the remainder of the simulation, which broke the rocks into smaller pieces and finally into a fluid. This was achieved with particles. On top of that, were smoke, dust and debris.

Dumont points to three challenges: setting up the lava and pyroclastic workflows and getting the scale right. The most difficult shot was the draining of the lava from Zeus to Kronos. This required all the setups working together, replacing the environment with a CG one and re-projecting the characters and blending together the different lava setups and adding the atmospherics.

"I think this was the biggest project we've had in terms of its complication," Dumont concludes. "We achieved a good thing for this process and we developed our pipeline based on that. And also we developed some tools that are very interesting for the Kronos animation."

Bill Desowitz is former senior editor of AWN and editor of VFXWorld. His blog is Immersed in Movies (www.billdesowitz.com), he's a regular contributor to Thompson on Hollywood at Indiewire and he's the author of the upcoming James Bond Unmasked (Spies), which chronicles the 50-year evolution of the iconic superspy from Connery to Craig.