Despite sharing the same material qualities, the warriors of the terracotta army had to be modelled differently to the Emperor, because of the vast number of characters involved in the scenes.

The soldiers are portrayed purely as terracotta statues brought to life – not as mummies encased in a clay shell – and so moved in a more solid fashion without cracking and shattering.

Working from a life-sized model of a terracotta warrior used on-set as a lighting reference, along with tons of photographic material relating to China’s real terracotta army, found in 1974, the team built the soldiers in 3D using Maya.

Much like the real terracotta warriors – each of whom is unique, and is believed to have been based on a real individual – Cohen wanted the film’s CG soldiers to be highly individualized.

Armies of the undead

In addition, the film script called for a rival army of the risen dead, called the Foundation Army because they had been buried on Emperor Qin’s orders in the foundations of his great wall. Consisting of desiccated mummies and partial skeletons, they fight the terracotta army alongside the film’s live actors.

“Rob was after a very specific look for the foundation army,” says Larsson. “They had to look supernatural yet move in an organic, human way, with a colour palette that reflects the fact that the bodies had been buried in the wall for thousands of years.”

To generate enough variety for this army, a number of initial models were built for the characters from which the Digital Domain team then swapped heads, bodies, and clothing to create a full army.

“We also worked with different levels of decomposition,” adds Larsson. “That way, we had a few layers for each character, so we could reveal different layers all the way down to the bone-structure.”

Both armies posed their own unique compositing challenges. For the terracotta soldiers, the hardest thing was maintaining the subtle hue variations inherent in terracotta. This had to be achieved without sacrificing the individuality of each soldier, while still making them live in the live footage.

“This would change depending on the lighting of each shot,” says Andre. “In addition, the soldiers needed to connect to the ground, leave footprints, cast shadows, kick up dust and behave in a manner that would suit the action in the scene – and it all had to look like we just happened to catch it on camera.”

Colour control

Key to compositing the Foundation Army was maintaining a good colour balance, Andre continues. This was complicated by the fact that the characters’ skeletal structure had to have a certain colour and quality, and each scene’s lighting depended on how much of a particular character’s clothing, hair and flesh remained.