The Making of God of War III - Prima Games

The Making of God of War III

by Prima Games Staff

Post-GDC and in the wake of last week’s gargantuan Uncharted 2 post-mortem, Digital Foundry’s “downtime” this week was spent playing the UK’s – and most likely the world’s – number one videogame, God of War III.

Previously we’ve covered the Sony Santa Monica team’s work in radically improving visuals and performance of the game since the release of the E3 demo. This time, we’re focusing on how state-of-the-art technology meets a vision of an epic, interactive cinematic experience that makes God of War III one of the most involving, visceral and exciting videogames ever made.

Core to the whole experience is the quality of the artwork that the Sony Santa Monica team generates. Those who’ve played the God of War Collection will have seen how the attention to detail the artists put into their work almost seems to exceed the resolution requirements of the host platform itself, to the point where the PS2 HD “remastering” acquits itself well even up against native current-gen titles.

In God of War III, detail levels in terms of both texturing and geometry are a massive step beyond what has been seen in the previous games. Programmable pixel shaders add textures and effects that give a whole new dimension to the quality of the final work.

It’s a true generational leap, and performance of the new game, in terms of frame-rate, is in the same ballpark as the previous two God of War titles.

Video: God of War III’s performance throughout the game varies from around 30FPS right up to 60, depending on scene complexity. V-sync is engaged from start to finish, as it was in the God of War Collection.

In terms of the character creations themselves, concept art and a low-poly mesh from Maya is handed off to the 3D modellers, who create the basic models using a sculpting tool known as Z-Brush. These models are then given detail – painted in via Photoshop – before being passed along the next stages in the art pipeline to the character riggers and animators.

Kratos himself is an extremely detailed model, though it’s interesting to note that the raw polygon count is considerably lower than the 35,000 or so that comprise the in-game model of Nathan Drake in Uncharted 2. That the Spartan maniac looks so good is all down to the individual make-up of the model. The poly count is just one element of the whole composition.

“We use as many polys as it takes,” art director Ken Feldman says. “Off the top of my head, texture sizes for these character are quite big. I think we are using 2048s for the lower, upper body and head. Each character gets a normal, diffuse, specular, gloss (power map), ambient occlusion, and skin shader map. We also use layered textures to create more tiling, and use environment maps where needed.”

“If you look at Kratos on the PS2, he is about 5000 polygons,” Feldman says. “He is about 20,000 polygons now. I think he had three textures on the PlayStation 2. I think he has at least 20 textures on him now. The animation data on him is probably about six times as big.

“So Kratos went from being a couple of megabytes to now, it would actually take two PS2s to fit his memory footprint all in there. He is always loaded in the game. The other thing is that he has many more weapons, too. He can load between all of those different weapons, so all that stuff is loaded with him also, and all of the move sets.”

A new technique known as blended normal mapping adds to the realism of the basic model and hugely enhances the range of animation available. Muscles move convincingly, facial animations convey the hatred and rage of Kratos in a way we’ve never seen before.

The system operates to such a level of realism that wrinkles in the character’s skin are added and taken away as joints within the face of the model are manipulated. The musculature simulation is so accurate that veins literally pop into view on Kratos’s arms as he moves them around.

God of War III’s main protagonists are all animated by hand, simply because it was found that the animators themselves produced more effective work than basic motion capture from the actors offered. However, for secondary characters, Image Metrics’ performance capture system recorded the voice actors’ facial movements and mapped them on a per-pixel basis to the 3D models, with touch-up work carried out by the Sony Santa Monica team.

“The satisfaction comes from seeing Kratos in the game and saying, ‘wow, that’s him’,” explains lead character artist Patrick Murphy. “You can see his veins, you can see him breathing. It looks better than the cinematics. That’s the satisfaction.”

In terms of character movements, over and above the pre-defined animations created by the team, the God of War technical artists also created secondary animation code. Why hand-animate hair, or a serpent’s tail, when the PS3 itself can mathematically calculate the way it should look? The system’s called Dynamic Simulation, and its effects are subtle but remarkable, accurately generating motion that previously took the animators long man-hours to replicate.

Video: The gorgons are a good example of how mathematically generated animation merges seamlessly with custom rigs created by the animators.

“From God of War II to God of War III we’ve used Dynamic Simulation more and more to do more secondary animations on the characters,” explains Giovanni Luis, manager of the tech art team. “Before, on previous games, the hair or the cloth would be stiff, it would be modelled into the creatures. Now we’re actually adding motion to those pieces so you will see hair and cloth moving.”

“Towards the end of the previous game, in collaboration with Jason Minters, I created this dynamic system that uses the Maya hair system to drive a series of joints,” adds technical artist Gary Cavanaugh. “Each of the snakes on the gorgon’s head is independently moving. The animator did not have to individually pose all of these animations but they do have control over the physics… it improves a lot of the workflow for animators.”

One of the most crucial elements of the cinematic look of God of War III is derived from the accomplished camerawork. Similar to previous God of War epics – and in contrast to Uncharted 2 – the player actually has very little control over the in-game viewpoint. Instead, Sony Santa Monica has a small team whose job it is to direct the action, similar to a movie’s Director of Photography.

Think about it: so long as the gameplay works, and works well, having scripted camera events ensures that the player gets the most out of the hugely intricate and beautifully designed art that the God of War team has put together. When running from point A to point B, why focus the camera on a piece of ground and wall when instead it can pan back to reveal a beautiful, epic background vista?

Sony Santa Monica actually has four team members looking after this, while a good proportion of one of the programmers’ time and effort is also spent making this all-important element of the package looking right.

“Cameras start by the design sheet being delivered to us by the level designer – that’s the most basic form,” says camera designer Stephen Peterson. “We put in all the cameras for the design sheet. Once the cameras are in and it’s been playtested and it’s been proven to be a good concept, we go forward with it and it gets sent off to the art department.”

“That’s where they’ll spend months – sometimes – making these areas look really epic,” adds lead camera designer Mark Simon. “They’ll hand it back to us and lot of the time it’ll be a little bit different and we’ll need to adjust some cameras.”

“Once the art has come back in and someone has spent a year building that level they can be very touchy if they spend a year styling this formation and my camera goes right past it,” explains Stephen Peterson. “We try to do our best to show off everyone’s hard work.”

While striving for a cinematic feel that showcases the best of the designers’ efforts, the cameras themselves also serve as guides to the player. The basic viewpoint in just about any traversal scene acts like a shepherd of sorts, pushing you in the right general direction. While players might crave an Uncharted-style free camera mapped to the second analogue stick, that’s not the way Sony Santa Monica rolls. Its pursuit of the cinematic experience is tied closely to having control of the player’s perspective on the action, and the game world.

While strict camera controls may have a bearing on “budgeting” a scene from a technological standpoint, God of War III doesn’t apply in this regard as the viewpoint is dynamic, adapting to the gameplay and constantly striving to give the player the most satisfying outlook of the action.

“The camera is not fixed. It is highly scripted to provide a highly cinematic play experience, yes, but in no meaning of the word is the camera fixed,” director of technology Christer Ericson explained on the Beyond 3D forum.

“Within the setup cinematic parameters there is a lot of room for the camera to adjust to the action that happens on the screen (where the player is, where the enemies are, etc). Because of the amount of adjustments the camera system can make automatically, there are very few assumptions that can be made about what to render or not render…

“We could easily allow the user full control of the camera during gameplay. The reason we do not is because we feel it breaks the cinematic experience that we have carefully crafted, not because there is some geometry missing if you turn around…”

Ericson likens the implementation to the dolly used in film-making, with the camera on an arm, able to move in, out, pan, zoom and tilt.

“Which of these movements the camera makes is dependent on parameters that our camera designers have carefully set, but ultimately on the location of the player and the enemies on screen,” he says. “This decision is made at run-time, not tool-time… for every game frame, we determine at run-time the position and orientation of the camera. In other words, the possible movement space for the camera is an irregularly-shaped 3D volume, not some simplistic ‘glide path’. As a general rule, neither position nor orientation of the camera within this volume can be predetermined for any particular gameplay moment.”

The relationship between the camera guys and the other departments in the team mean that while you might think a scripted camera to be “easier” for the developers to deal with, the logistics of maintaining that all-important cinematic experience are probably just as hard – maybe even harder – than simply handing over control to the player.

“Every level requires a camera design stage that has potential cross-dependencies with every other department, well, other than concept art. That alone tips the scheduling and budgetary considerations seriously against us. This is not an easy road,” says Sony Santa Monica’s Phil Wilkins.

“The only performance benefits are that we can focus asset creation quality on what we want to look at. Sometimes this means that we don’t need to build the back wall of a room. Or we can unload an area behind us that we can no longer see. Although often we’ll just swap it for a lower-detail version of the same area (think of the horse/chain section of God of War II).That’s entirely in the domain of the artists and designers though.”

Camera is a crucial element to God of War, and the fact that the player isn’t in control means that for some of the puzzling stages, it’s important for the scripts to include an overall view of the surrounding area. In this case, an on-rails camera provides the goods, and is also used to good effect to get the best possible viewpoints on some of the game’s most spectacular levels. The game sets out its stall in an enormously effective manner in the very first level, which pits Kratos up against the god of the oceans, Poseidon, while circumnavigating Gaia – a titanic figure as tall as the Sears Tower, over 1400 feet high.

Video: An abridged edit of the first incredible level in God of War III, complete with frame-rate analysis. Many of the new tools and techniques in delivering a cinematic experience get their debut here.

As you can see from the video, this initial stage from God of War III showcases many of the technological improvements the team made for the sequel. Not only do you see a range of dynamic, on-rails and combat cameras, but you also see that Sony Santa Monica has taken a stab at its own rendition of Naughty Dog’s dynamic object traversal system – the whole level can be animated and moving, and the action on those moving surfaces is affected accordingly.

“There was no way to do this level of scale on the PS2 – just not enough memory,” says Ken Feldman. “Most games are centred around a room-to-hallway design because engines do that really well. It’s really easy to put tons of detail in small rooms but it’s a whole different challenge to create a massive spectacle – and that’s the challenge we undertook.”

RAM management must surely be immensely challenging here. Textures and geometry need to look sufficiently detailed at both the micro and macro levels, and to enable seamless transitions between the two, both would need to be kept in the system memory. To illustrate, Kratos may well be nothing more than a small speck in some of the shots, but that memory-intensive 20,000 polygon model is still in RAM.

Perhaps part of the solution comes from the data streaming system running continuously in the background. Once you’re in gameplay, God of War III has no pauses for loading whatsoever, and runs with no mandatory hard disk installation, in common with most Sony first-party games. Everything is being streamed from BD to system memory in the background.

Perhaps most astonishingly of all, the final God of War executable file that sits on that mammoth Blu-ray is just 5.3MB in size – uncompressed, and including SPU binaries – in a project that swallows up a mammoth 35GB of Blu-ray space (40.2GB for the European version with its support for multiple languages).

As Tim Moss pointed out on his Twitter feed, it’s a “point of pride” for the team as it leaves “more memory for content” – an ethos the team has worked with for some time: the original God of War on PlayStation 2 ran from a similarly miniscule 1.2MB of code.

The conclusion of our Gaia video on the previous page – showing Poseidon’s sticky end courtesy of Kratos’ bludgeoning fists – introduces players to another perspective innovation: first-person kills. As the player completes the rout of a boss character, the viewpoint shifts to the victim, with the entire screen taken up with the Spartan berserker pummelling his now-defenceless opponent. The result is a vicious masterpiece of art, direction and technology.

“From the get-go I came up with the idea of the first-person kill in giving a new perspective on Kratos’s kill sequences,” says Adam Puhl, lead combat designer. “Immediately everyone was sold when they saw it in-game… you get to see the impact of Kratos’s attacks and see how Poseidon feels as he’s getting completely torn apart.”

Another core part of God of War III’s cinematic look and feel comes from the basic setup of the framebuffer, and the implementation of HDR lighting. Two framebuffer possibilities for HDR on the PlayStation 3 include LogLUV (aka NAO32, used in Uncharted and Heavenly Sword), and RGBM: an alternative setup that has found a home in Uncharted 2 and indeed in God of War III.

The basic technical setups for both formats are covered elsewhere (though GOWIII uses its own version of RGBM), but in terms of the final effect and what it means for the look of the game, the result is a massively expanded colour palette which gifts the artists with a higher-precision range of colours in which to create a unique, stylised and film-like look.

Opting for the RGBM setup over LogLUV means a significant saving in processing, although some precision is lost. The degree of that loss isn’t exactly apparent to the human eye, and we can assume it becomes even less of an issue bearing in mind that the final image is transmitted to your display downscaled over the 24-bit RGB link in the HDMI port.

In terms of post-processing effects, the game is given an additional boost in realism thanks to an impressive implementation of motion blur. Superficially, it’s a similar system to that seen in previous technological showcases like Uncharted 2: Among Thieves and Killzone 2, and helps to smooth some of the judder caused by a frame-rate that can vary between anything from 30 frames per second to 60.

Most games that implement motion blur do so just on a “camera” basis – that is, the whole scene is processed – an effect that of variable effectiveness in terms of achieving a realistic look.

According to Sony Santa Monica’s Ken Feldman, motion blur is calculated not just on the camera, but on an individual object and inner object basis too.

Video: God of War’s camera and object motion blur is a subtle but effective contribution to the cinematic look of the game. Here at 30 per cent speed, the effect is more easily open to analysis. Hit the full-screen button for HD, or click on the EGTV link for a larger window.

The basics of the motion blur system effectively mimic what we see on the cinema screen. Movies run at a mere 24 frames per second, but give the impression of being significantly smoother. While filming, the shutter of the camera stays open for around 0.04 seconds. During that window of time, movement in the captured image is blurred. It’s that phenomenon that the tech seeks to mimic in God of War III: more cinematic, more realistic.

Another key effect in producing a filmic look to God of War III comes from development of new anti-aliasing technology. Removing the jaggies associated with videogaming obviously helps to create a more pleasing appearance.

Initially the game used the RSX chip to carry out a traditional 2x multisampling anti-aliasing effect. This, combined with the game’s lack of high-contrast edges, produced an extremely clean look in last year’s E3 demo. For the final game, the Sony Santa Monica team implemented a solution that goes way beyond that.

According to director of technology Tim Moss, God of War III worked with the Sony technology group in the UK to produce an edge-smoothing technique for the game that the developers call MLAA, or morphological anti-aliasing. Indeed, Moss’s colleague Christer Ericson took us to task on the specifics of MLAA a few months back in this DF blog post, revealing that the team has put extensive research into this in search of their own solution.

“The core implementation of the anti-aliasing was written by some great SCEE guys in the UK, but came very late in our development cycle making the integration a daunting task,” adds senior staff programmer Ben Diamand.

The specifics of the implementation are still unknown at this time (though Ken Feldman suggests it “goes beyond” the papers Ericson spoke about in the DF piece) but the bottom line is that the final result in God of War III is simply phenomenal: aliasing is all but eliminated and the sub-pixel jitter typically associated with this technique has been massively reduced compared to other implementations we’ve seen.

Video: The implementation of MLAA works beautifully in eliminating edge-aliasing within the game. Only in the final shot are the artifacts of the technique really apparent. Click on the full-screen button for HD, or else use the EGTV link for a larger window.

The custom anti-aliasing solution is also another example of how PlayStation 3 developers are using the Cell CPU as a parallel graphics chip working in tandem with the RSX. As Richard Lemarchand discussed in his Uncharted 2 post-mortem, the basic theory is all about moving tasks typically performed by the graphics chip over the Cell. Post-processing effects in particular work well being ported across.

The more flexible nature of the CPU means that while such tasks can be more computationally expensive, you get a higher-quality result. The increased latency incurred can be reduced by parallelising across multiple SPUs.

In the case of God of War III, any given frame typically takes between 16ms and 30ms to render, give or take a millisecond or two. The original 2x multisampling AA solution took a big chunk of rendering time, at 5ms. Now, the hugely more impressive MLAA algorithm takes a total of 20ms of CPU time. However, it’s running across five SPUs, meaning that overall latency is a mere 4ms. So the final result is actually faster, and that previous 5ms of GPU time can be repurposed for other tasks.

While the detail that the Sony Santa Monica team has put into the characters and environments is clearly immense, it’s the combination with the pure rendering tech that gives the game its state-of-the-art look and feel. The new God of War engine thrives in its handling of dynamic light sources, for example.

“[Dynamic lighting] is one of the big features of our engine. We built it around being able to use up to 20 dynamic lights per game object,” Ken Feldman explains.

“The light can be big or small, it doesn’t matter. In the end, I believe we support up to 50 dynamic lights per game object. We are not using a deferred lighting scheme. Our lead programmer Vassily Filippov came up with this amazing system during pre-production… We can place lights in Maya and have them update in real-time in the game on the PS3, it’s like being able to paint with lights. Lighting is a fast and a very enjoyable artistic process.”

Where there is light, there is a shadow. Or at least there should be. On the majority of videogames, shadowing tech is fairly basic. Producing realistic shadows is computationally expensive, hence we get a range of ugly artifacts as a result: serrated edges that look ugly up close, or cascade shadowmaps that transition in quality in stages right before your eyes.

God of War III stands out in this regard simply because you don’t tend to notice the shadows. They’re realistic. The human eye is drawn to elements that stick out like a sore thumb, and that includes shadows. State-of-the-art techniques result in a very natural look. The result is subtle and it works beautifully.

As well as working with his team mates in helping to build the PS3 renderer from the ground up, Sony Santa Monica programmer Ben Diamand spent around three years gradually developing the deferred shadowing system employed in God of War III, that works beautifully in eliminating the artifacts and blending dynamically-generated shadows along with others that are pre-baked into the scenery.

Perhaps the only slight disappointment with the shadows in God of War III is that their use and impact in direct gameplay is limited. There are some nice sequences revolving around direct use of dynamic light, but the only time shadows are an intrinsic part of the task ahead of you is when you use them to dodge the incoming fist of a very angry Titan.

The amount of effort that went into just this one element of the overall image quality is quite extraordinary, but Sony Santa Monica’s Ben Diamand stresses that it’s just one part of a developmental process that saw many programmers tackle different areas in building the renderer for God of War III, of which the shadowing system was just one component part.

“It’s not that we could afford to spend a ton of time on any one thing that made Sony Santa Monica shine; I’d instead say that it’s the versatility of the staff – art and design included – that really made it happen,” Diamand tells us.

“That coupled with having programming managers like Christer and Tim who helped by suggesting good ideas and especially by running interference for us so we had the time to properly implement and iterate over all of our ideas – those things were truly key.”

Preliminary work on the PlayStation 3 tech actually kicked off while the main team were still working on God of War II. Ben Diamand himself spent a year with the ICE team in Santa Monica working with the early PlayStation 3 simulator hardware before moving onto direct God of War III research. Before there even was a God of War III team as such, Sony Santa Monica staff were laying the technological foundations for the new game.

“Vassily did large amounts of work on the dynamic lighting algorithms, Naty helped a bunch with getting the particular look by implementing many cool shading ideas and I worked on the low level renderer which included a number of iterations on the shadow system,” Diamand says.

In addition to the shadowing tech, Diamand was responsible for the core renderer and associated optimisations, all kinds of SPU work, the HDR implementation, tone mapping, bloom, the effects framework and tools work among other tasks. Similarly, other members of the programming team found themselves donning many different hats during the development cycle.

“Vassily and I, with help from Naty Hoffman a bit later, essentially built most of the PS3 renderer from the ground up,” Diamand adds.

“We later hired Jim Tilander who did some very good SPU rendering and collision system work, Cedric Perthuis who did a fantastic job with effects like rain, some good shader optimisations, anti-aliasing, depth of field and god rays among others, and Eric Smolikowski who joined us near the end and did really awesome implementations of motion blur, dynamic refraction/reflection and dynamic water, along with helping me do some of the drop shadow integration.”

Sony Santa Monica’s artistic and technical achievements are clearly considerable, but what is truly impressive is the team’s commitment to continually refining and optimising code, right up until the very closing stages of development. It’s an impressive juxtaposition of the team’s passion in getting the very best product out there: Ben Diamand can spend over three years adding to, tweaking and perfecting his shadowing tech among his other tasks, but at the same time, right up to the creation of the final gold master, the team was still optimising performance.

According to director of technology Tom Moss, in the last week of development, after the first review copies had been dispatched, programmer Cedric Perthuis continued refining code, achieving impressive performance gains to the tune of around eight per cent for the final game.

God of War III is a special game by an immensely talented team, backed not only by a colossal $44m budget, but also with the collaborative know-how of some of the world’s best developers and access to the resources of Sony’s own dedicated engineering groups.

It’s games like this, along with Uncharted 2: Among Thieves and Killzone 2, that give the platform holder ownership of the bleeding edge of console gaming technology in the current generation.

It also makes a very convincing argument that there’s plenty of life left in the system yet. God of War III is just the first PS3 title from Sony Santa Monica, and already director Stig Asmussen is hinting that we can expect “a lot more” from the current God of War III engine.

This piece contains material derived from almost 2.5 hours of ‘Making Of’ material found on the God of War III disc itself, used with permission. Complete the game, unlock the lot and watch them all for some idea of the legendary efforts put in by the Sony Santa Monica development team.

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