Axis heads back to the Killzone

Glasgow-based animation studio Axis Animation has created a stunning cinematic CG sequence that forms a dramatic introduction to the next instalment of the epic Killzone game franchise.

Released in February for PS3, Killzone 2 is the much-anticipated next instalment in Guerrilla Games’ popular first-person shooter game franchise.

The games’ action is set in a future space world colonized by humans, where a splinter group of colonists on the planet Helghan has evolved over the years to become an entirely new race: the Helghast.

After a bitter war against mankind and a subsequent period of isolation, the Helghast forces begin a new assault, starting with the neighboring planet of Vekta.

Killzone 2 picks up the story two years after the attack on Vekta, with the Interplanetary Strategic Alliance (ISA) troops taking the fight to the enemy’s home world of Helghan.

Setting the scene for the game is an ambitious three-minute cinematic sequence directed and produced by UK studio Axis Animation, who had previously created the introductory sequence for the original game.

Consisting of a single unbroken camera move, the sequence starts in close-up on the face of the Helgan emperor Scolar Visari (voiced by actor Brian Cox) as he gives an impassioned speech to the Helghan people.

The opening camera pulls back to reveal that Visari is in fact being televised via an ISA news report watched intently by Killzone 2’s principal character, Sergeant Thomas ‘Sev’ Sevchenko.

From here, the camera takes the viewer on an epic journey following the ISA invasion fleet departing their base on Vekta, out into interplanetary space and down into the hostile atmosphere of the planet Helghan.

“When we were offered the opportunity to work with Sony and Guerrilla again on Killzone we jumped at the chance,” says Axis executive producer Richard Scott.

“We spent a lot of time during the pitch phase exploring different styles and look development for the intro, and it was clear to Sony that we were passionate about the project.”

Following the pitch phase, Axis director Stuart Aitken and his team worked closely with both SCEE and Guerrilla to further refine the concept, scripts, and storyboards.

“I would say that the pre-production stage was very much a collaborative effort. Guerrilla was quite focused in terms of knowing what it wanted to ensure the overall look and specific story elements tied in with that of the game itself,” says Aitken.

“Most game cinematic projects tend to be fairly close collaborations,” he adds. “You have to be sensitive to the fact that you’re dealing with someone else’s baby and that there have possibly been literally millions of man hours poured into establishing aspects of the game before you come along.”

The most challenging part of the sequence was the need for one unbroken camera move that traverses huge distances through space, while handling numerous changes of scale.

This raised both creative and production issues for the Axis team. “It’s only when you don’t have cuts that you realize how much you really depend on them across almost every facet of shot production,” says Aitken.

“They’re very useful for organizing work and allowing you to section up a large project into discrete chunks that you can then assign to various people. Without them it becomes much harder to say to team members, ‘your stuff starts here and ends there’,” he explains.

A long shot

To allocate work among the team, Aitken divided the sequence into three main sections, although he took responsibility for most of the camera animation himself.

“It became almost impossible to delegate, as it was so integral to the direction of the piece,” he says. Creatively the single camera move was a great challenge, he notes.

“We had to pretty much throw the boards out the window in several places, because there was just no way that 2D storyboards could fully predict how this intensely 3D move was going to work,” he says.

“Although they still performed an important role in helping define ‘key markers’ for where the camera needed to get to next, often the transitioning moves had to be invented during 3D layout.

"The complexity of the whole camera animation process meant that there were a few bottlenecks in terms of getting stuff locked down so that the animators could get to work.”

Several technical issues with the single camera move were centered on scale – the key problem was getting the camera to transition from one jump in scale to the next across the entire sequence. “The usual tools you have to edit camera animation – graph editors and so on – become compromised when you’re trying to edit one spline curve that has to represent extreme changes in scale, or seamlessly transition between one type of angle and another,” says Aitken.

“There were surprisingly few ‘cheats’ on the camera... the couple we originally introduced to help break the piece up into a few large chunks ended up being made continuous in 3D again, as the transitions just didn’t look right otherwise.”

To further add to the challenge, any changes made by the team to the camera move in an earlier part of the sequence had frustrating knock-on effects, or would put a carefully judged acceleration slightly out of sync.

Nor could Aitken use a single set of camera constraints throughout the entire sequence. “We got around that by evolving a methodology which involved animating lots of separate cameras for various sections – with their own individual constraint set-ups dependant on the subject – then we weighted blends between these with one ‘uber-camera’ which then had to be baked and refined further and perhaps blended again,” explains Aitken.

“It was a bit cumbersome, but it worked and I really don’t think there was another way to achieve what we did.”

Most of the really difficult bits involved circular moves where the Axis team had to transfer the focus from one aspect to another or get in very close to objects while crossing huge distances. The whole layout process depends on the camera as the focus.

“We frequently had to do some quite complex set-ups to translate whole chunks of layout into odd angles or complicated constraints systems to suit the camera move,” says Aitken.

There was also a more fundamental issue with scale: as the animation goes from a close-up of Visari’s eyeball through to interstellar space occupied by spaceships that are half a kilometer in length and back again, handling every element at a realistic scale would have resulted in problems with floating-point accuracy.

Rather than cheat the 3D camera, which had to be seamless, Aitken and his team cheated the scale of the elements – the planet and ships – within the space section.

“The fact that space is a void allowed us to do so unnoticeably,” he says. The Killzone 2 project’s success is testimony to Axis Animation’s exemplary character work, particularly in the creation of the Scolar Visari character that bookends the sequence.

As he is seen in extreme close-up, the team had to pay great attention to wrinkles, blemishes, skin shaders and facial deformation to ensure a realistic and impressive performance.

Character work

All characters in the sequence aside from Scolar Visari were game assets built by Guerrilla and supplied with rigs, skin weights and facial set-ups. Some refinement of these in-game assets was necessary, including extracting detail from original ZBrush files in order to create high-resolution displacement maps as required for the film-quality sequence.

As a starting point for the character animation, Axis held a motion-capture session early on in production at Audiomotion’s studio in Oxford. Yet even with large amounts of mo-cap data captured, the team had to add to these sequences by hand using traditional keyframing techniques.

Facial animation was also hand keyframed using a blendshape system controlled by a visual user interface built from sliders and joysticks that was made from curves and attached to each character’s head, explains Aitken.

“We added to the rigs so we could switch limbs to IK where necessary, which was usually when two-handed weapon contact was seen in close-up,” says Aitken.

“The need to blend and add to the mo-cap data was compounded by the fact the cameras were animated after the shoot, so often we had to improvise new animation to suit the camera move.”

Along with 2D applications such as Photoshop, Axis used an arsenal of high-end tools on the project. Modo, ZBrush, and Maya were used for modelling, with the later also used for layout, camera and character animation.

Houdini and Mantra were used for lighting shading, VFX animation and rendering, while compositing was completed in Fusion. “I would single out Houdini as being the backbone of our current pipeline,” says Aitken.

“We still use Maya, mainly because our animators like to use it and its animation tools are quite polished, but Houdini is more pipeline-orientated and flexible as a workhorse 3D application – especially if you want to do complex technical things without having to write huge swathes of code.”

This aspect of Houdini proved incredibly important when it came to finding solutions to the sequence’s many visual-effects challenges.

These ranged from dramatic ship explosions, dense planetary atmospheres filled with storm clouds, battlefield smoke to slow-motion ground explosions and gruesome blood splatters.

Houdini also helped the team to create the many different environments that feature in the sequence. These environments were created using a mixture of modelled, textured and shaded 3D elements and matte paintings.

For the Vekta space port location, for example, Axis built highly detailed models of the base corridor, exterior bunker entrance, launch pads, cradles and the spaceship themselves, with high-resolution textures applied to these models after UV mapping.

“We spent some time working on methods to allow us to render soft raytraced reflections with ambient occlusion in realistic rendering times,” says Aitken.

Sergio Caires, a senior Axis 3D artist, built these reflections into the standard ‘uber-shader’ in Houdini and wrapped the resulting enormous shading network (3,000-plus nodes) up in a simple interface so that the artists shading each asset could define surface qualities quickly and efficiently.

“This is where Houdini really shines,” says Aitken. “Trying to do this in any other package in the timescale we had would have been a nightmare or simply impossible.”

According to Aitken, the spaceships themselves were a huge undertaking to build and texture from scratch. Many hours were spent in Photoshop working with images of real-world naval vessels to gather details such as steering jets, navigation beacons, battery arrays as well as realistic surface texture references.

Each ship employed around 60 separate texture maps, each of which were around 2,000 pixels in size – and all of which had extensive panel detailing on.

“The attention to detail here was pretty insane,” says Aitken. Scenes were output using Houdini’s Mantra rendering engine in separate passes for shader parameters – including diffuse, specular, reflection, and occlusion – as well as utility passes for other elements such as object mattes and depth of field.

Given the number of separate detailed elements in each scenes, the comps themselves were huge, says Aitken.

“Mantra’s flexibility in terms of loading geometry into RAM at render time and its object instancing helped enormously in terms of rendering the sheer amount of detail we had,” he says.

Once the full sequence was rendered, grading and finishing was done in Flame at Scramble in London, with Guerrilla Games completing sound design and music.

Axis’ hard work and attention to detail have been rewarded by an overwhelmingly positive response to the sequence. “We’ve been blown away by the amazing reaction from both the client and the game buying public,” says Richard Scott. “We always look forward to a huge challenge – and this project definitely threw a lot of those our way.”

Creating the Helghan battle scenes

The battle sequence on Helghan was one of the most difficult sequences to lay out, according to director Stuart Aitken, and one for which the initial storyboards were the least help in determining the final camera move.

“It was very difficult to get the camera move to work fluidly in this part and to transition effectively from one group of doomed soldiers to the next at just the right time to capture their demise from an interesting angle,” he says.

“We had shot a lot of ‘death scene’ motion capture but even with this, it was quite hard to work out the relationship between the captured animations and the camera.”

Complicating things further was the need to move in and out of slow motion as the ISA marines are being shot down in trails of blood or blown up in front of the camera.

“Not only did the character animation have to be slowed down seamlessly, so too did all the particle and volumetric effects, which was tricky given that these were being created in Houdini and the characters were animated in Maya and then exported to Houdini for lighting and rendering via vertex caches,” says Aitken.

“In the end we did everything in real-time and built some time-warping surface operators in Houdini to manipulate them all at the same time. Choreographing the right pace required playing about with rough speed changes using some 2D-based time-warping tools on some scene playblasts.”

The model of planet’s surface involved a large number of polygons and extensive use of displacement mapping. To solve this Axis created a few procedural tools in Houdini, which meant extreme levels of detail could be rendered relatively quickly.

To portray the inhospitable Helghan atmosphere, custom displacement shaders were written that used extensive subsurface scattering to create a dense cloud effect.

“Our Houdini volumetric tools were used again to create all the ‘fog of war’ effects you see during the battle scenes – essentially these use minimal particles that are given a radius and ‘blobbed’ together before various fractal noises are moved and swirled through them to give a more detailed impression of smoke or fog,” says Aitken.

Creating the face of Scolar Visari

Working with Guerrilla Games, Axis went through a separate design and pre-production phase for the creation of the sequence’s key character, Scolar Visari.

Having decided to enhance the appearance of the previous Visari character, which Axis had created several years ago for the original Killzone intro, Aitken and his team began by looking at various reference faces that were felt to represent some aspect of Visari’s character, along with updated 2D concept art provided by the game’s developer, Guerrilla.

Axis modeller Ensar Yanar built a polygon mesh in Maya, which he then refined in ZBrush, updating the texture maps for colour, specularity and displacement at the same time.

The maps were then used to build the skin shaders in Houdini, which had a slightly more advanced treatment in terms of reflection, specularity and subsurface scattering than required for the other characters in the sequence.

The base mesh was rigged in Maya using weighted blend shapes and various secondary deformers to create effects such as jowel wobble. Finally the model was hand animated to the audio track actor Brian Cox had recorded earlier.

“The main challenge for the two sequences that featured Visari was just how much focus there was on his performance and how tight a close-up we used,” says Aitken.

“I think the final sequence at the end turned out very well – the simpler lighting treatment we were able to use for that really worked and the subtly conveyed menace that he delivers in that end scene is very believable.”

Photo-real faces

One of the standout features of the sequence is the highly realistic way the characters move – and in particular, the stunningly detailed sections featuring Scolar Visari.

This is even more impressive than it seems, as unlike much of the other character work it was created without the help of motion-capture data.

”It would have been nice to have had a full facial performance capture for the character, but I don’t think Brian Cox’s schedule allowed for this,” explains Aitken.

The single-shot sequence completed by Axis aims to give a sense of Killzone 2’s huge scope, taking in everything from exploding space stations to humanscale drama on the ground.

Axis Animation worked closely wth Killzone 2 developer Guerrilla Games on storyboards to ensure the sequence was a perfect fit for the game’s feel and plot.


Project: Killzone 2 introduction
Client: SCEE and Guerrilla Games
Software: Adobe Photoshop, Autodesk Flame, Autodesk Maya, Eyeon Fusion, Luxology Modo, Pixologic ZBrush, Side Effects Houdini

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