Scanline VFX created the CG water and the secondary animation of falling Persians. The decision to go all CG came about because there was no tank facility and no budget to build a giant boat model. 

On the composting side at Animal Logic, vfx supervisor Kirsty Millar worked with the artists to bring their sequences alive. "We worked on the whole of Battle One, which is the first time the Spartans clash with the Persians. This sequence is comprised of 176 vfx shots and runs to around eight minutes," she details.

Providing scene context, Miller explains, "The Spartans train all of their lives for combat and strategically use the landscape as part of their fighting tactics. In Battle One, they first arrange themselves inside a narrow canyon known as the 'hotgates,' so, although the Spartans are vastly outnumbered, the first wave of Persian infantry effectively has only one row of around nine Persians fighting one row of nine Spartans. This is the part of the sequence we called the 'hack n' slash' -- lots of fast cuts of hand-to-hand combat. The Spartans start to gain the upper hand and push the remaining Persian infantry over the cliffs of Thermopylae and into the ocean below. The Persian archers then launch a volley of millions of arrows that 'blot out the sun,' so the Spartans have to 'fight in the shade.' The Spartans 'tuck-tail,' crouching beneath their shields as the arrows bounce harmlessly around them. The Persians then send in the Cavalry, which the Spartans meet by forming a pointed phalanx in a narrow road bordered by steep cliffs, falling down to the ocean on one side. This again effectively reduces the huge Persian army to one-on-one combat, as only around four horses can fit on this narrow road. Needless to say, the Spartans defeat the last wave and live to fight another day.

Animal Logic worked on Battle One, which is the first time the Spartans clash with the Persians. This sequence is comprised of 176 vfx shots. In the "hack n' slash" section, The Spartans push the Persian infantry over the cliffs.

"The most complex shot for us was hg036_081, also known as the 'Crazy Horse' shot," she continues. "We called it this because Zack had the idea to use the same sort of camera rig that was used in the film 'Crazy Horse', which used a beam splitter to provide a synchronous pos and matte. Zack wanted to take it a step further and simultaneously record three angles, a wide, mid and close, through the same viewfinder. The three angles could then be 'nested' to make digital zooms. The action was recorded at high-speed, with lots of motion- interpolated speed ramping in post to highlight the action. There were technical issues with the camera rig on the day so a fairly low-tech compromise was arrived at. They simply bolted three cameras together on a dolly. The resulting slight offset of the angles meant we had to morph between each in order to re-align the framing. We tracked the wide angle and worked out the camera offsets of the mid and close, then rendered the 3D environment with the angle changes incorporated. We added Leo's CG spear and CG sword extension, lots of CG spear tips and ends, digital doubles in the background, CG debris, blood, a CG leg being hacked off, light rays, dust and atmos. The final shot was about 1,700 frames long.

"The sheer volume of footage for this shot, plus the number of CG elements to go into it, with the additional complication of multiple speed ramps throughout, meant this was the shot we felt was the most likely to use a huge amount of resources and generally go awry. We also wanted to keep the edit flexible, so that Zack could change the timings if he wanted this helped to guide our approach. Senior compositor Tony Cole oversaw the shot with 3D lead Andrew Jackson and 3D td Clinton Downs working out a very efficient and flexible pipeline. In the end, it ran incredibly smoothly and turned out to be a stunning moment on screen."

Screaming Death Monkey -- The Oracle
One of the creepiest sequences of the film involves King Leonidas seeking out the diaphanous Oracle and her grizzled keepers high atop a mountain. Screaming Death Monkey (SDM) of Venice, California, created the Oracle work. Jeremy Hunt, visual effects supervisor for SDM, explains that he had worked with Watts on previous projects, "so I think he was confident that we could produce a high level of work without constant supervision. He's familiar with my skills as an artist and supervisor as well as an owner and that, as well as our past relationship, created a level of trust. He also knows that we would be able to come in with a competitive bid, which is always is a big part of the vfx supervisor's concern."

Detailing their sections of the film, Hunts says, "All three sequences revolve around the Oracle that King Leonidas has to present his battle plan to. The first part is his journey to her temple up a steep rock formation. The challenge here was the big reveal shot at the end, which was an 827-frame shot with very extensive set extensions and CG environments. It was a great shot to work on because it had a little bit of everything in it: matte paintings, set extensions, compositing effects and it's straight out of the comic book so it was cool to see it come to life.