Just how much of that massive battlefield sequence from this season's "Battle of the Bastards" on Game of Thrones was CG? You'll find some answers in this spectacular VFX breakdown reel from Australian VFX house Iloura, part of the Deluxe Entertainment Services Group. There's more info in the press release, which you can read below.

Deluxe Entertainment Services Group (Deluxe) announces that its Australian animation and visual effects studio Iloura delivered a significant suite of work for the recent “Battle of the Bastards” episode of HBO’s tentpole series Game of Thrones. Working on the epic battle sequence for the Season 6, Episode 9 crescendo, Iloura’s team of visual artists used a mix of VFX and hand-crafted animation techniques to realize the vision for the bloody showdown.

Iloura’s work was led by VFX Supervisor Glenn Melenhorst on the pivotal sequences that bring to a head the heated feud that had been brewing between hero Jon Snow and his army of Wildlings, and the Boltons, led by Snow’s nemesis Ramsay Bolton.

The battle required many photorealistic horse and rider collisions, 3,000-strong armies, a mix of close-ups featuring live-action and CG humans and animals and massive crowd simulations, as well as hundreds of assets – CG armoury, weapons, flags, saddlery, body parts, and environmental assets such as blood, mud, smoke, fire and mist. Iloura was selected to work on the episode after presenting the show’s VFX Producer and Supervisor, Steve Kullback and Joe Bauer, with a series of tests presenting photoreal CG horses and riders colliding with other horses, rendered from various points of view. With Games of Thrones’ huge fan base, its exceptional production values and the scrutiny that is placed on the VFX across the series, it was essential that Iloura prove its strength via its rigging and muscle pipeline and the robustness of its animation team.

“Battle of the Bastards is shocking in its audacity,” said HBO’s VFX Producer for Game of Thrones Steve Kullback. “More shocking still that we pulled it off and so much credit for that goes to Iloura. We are up close and personal in this battle with CG horses and collisions right in front of the lens and we constantly needed to review Iloura’s shots side by side with the photography because it was hard to remember and even harder to see the difference between what was shot and what was added. Amazing."

To meet the animation challenges, Iloura’s artists researched and reviewed video references of horse behaviour in scenarios such as steeple chases, jousting, racing and associated accidents to garner an accurate representation to achieve the shots. Witness cams of horses captured on set proved to be valuable resources for the animation team as they provided multiple angles of reference for the same actions. Further, Iloura tapped its large library of animated clips to quickly assemble a blocking pass for shots, which became the foundation for animation that ended up on screen. Overall, the animation work consisted of motion capture, rotomation and key frame for horses as well as soldiers, building into a library of custom interactions and motion behaviours that could be used for both close-up shots as well as crowd shots built in Massive.

The initial brief was for the Wildling and Bolton armies to face off and then collide, but once production began, it became increasingly apparent that more complexity would be required. Each army comprised smaller factions with custom armour, weapons, flags, banners, saddles, bridles etc. Further, every asset needed a clean, pre-battle version as well as a muddy version, a bloodied version and a very-muddy-very-bloody variant.

To achieve the high-density shots and photoreal quality required, Iloura revamped its pipeline considerably and integrated systems. Its internal publishing tool ‘BOSS’ was improved to help with the number of assets, animation publishes and traffic going through the pipeline; Massive was integrated into the render and shading pipeline, and large sections were re-engineered to allow for more control and flexibility, with the pipeline moving completely to Alembic with rigging, animation and lighting achieved in Maya, FX in Houdini and compositing in Nuke using deep pixel compositing.

Game of Thrones “Battle of the Bastards” episode aired in the US on June 19 on HBO.