• Developer interview with Art Director Ken Feldman
    and Lead Animator Bruno Velazquez.

    CGSociety :: Game Production Focus
    10 September 2009, by Peter Rizkalla

    This is the kind of franchise that sets up a bar for the game industry to jump. 'God of War' first established itself as a new IP on the PlayStation 2 and has since breathed new life into the once dying action/adventure game genre. Art Director Ken Feldman and Lead Animator Bruno Velazquez saw this project as not just another challenge but an opportunity to really spread their wings creatively. Being that this is the first 'God of War' title to be released on the PS3, Ken Feldman and Bruno Velazquez give us a picture of how the development of 'God of War III' progressed from the beginning until now.

    Development on 'God of War III' actually began with a small team of coders and tech artists right after the release of the first 'God of War' on PS2. Later when the PS3 was released, development went into full effect. “First and foremost,” says Feldman, “When we started the process of bringing Kratos and the 'God of War' series to the PS3, we knew that visually we wanted the game to feel very grand. Around every corner we wanted to give the player something to look at that is stunning in its scale and beautiful in its detail. We have a lot of graphical features at our disposal including camera and object motion blur, depth of field, godray/lens flares, full screen color correction, distortions, dynamic lights, a robust shader system, dynamic muscle blending, skinned dynamic collision, etc. Our goal is to use each of these features in meaningful ways that add to the game play and story we are trying to tell.”

    © Sony Computer Entertainment America Inc.
    © Sony Computer Entertainment America Inc.
     
    © Sony Computer Entertainment America Inc.
    © Sony Computer Entertainment America Inc.

    The environments in the first two installments of 'God of War' were amazing and dwarfed Kratos to a relative ant size. Kratos would literally traverse through huge levels that were mounted on the backs of giant gods called Titans. A lot of production tricks were used to give the player the sense of environme nt size within the first two games but in 'God of War III', no tricks were required. “I know this word gets thrown around a lot when discussing 'God of War' and I don’t mean to be cliché,” Feldman explains, “but the best way I can describe the environments for 'God of War III' is ‘epic.’ We are now building full environments on Titans. What was a level in the first game would now fit on a Titan’s arm. We no longer need to do camera tricks to make an environment seem like its moving. We now have dynamic skinned collisions, so the play field is no longer static. Artistically we want the player to feel they are always part of a massive environment. Even if the player is in what appears to be an enclosed cave, the surrounding environment should be much larger. It’s also very important for us to make sure the worlds feel like they are alive. Thankfully the story of the game supports this and allows us to utilize those elements throughout the game.”

     

    Speaking of the story, 'God of War II' last left Kratos on the backs of Titan’s climbing Mount Olympus on a pursuit to overthrow Zeus and the gods loyal to him. Helios is the first of the gods to face Kratos’ fury. Kratos first knocks Helios off of his flying chariot then approaches Helios and tears his head off in a brutal fashion. As you do. Tearing flesh, bulging eyes, spewing blood and a painstaking amount of other impressive particle effects and shaders are utilized just to create this one scene. “The story we are telling is a horrific visceral version of Greek mythology. Moments like the Helios head rip, fit perfectly into that definition. Based on the fans’ reactions at E3 and Comic-Con, you can be sure there will more graphic moments in 'God of War III'."

    © Sony Computer Entertainment America Inc.
     
    © Sony Computer Entertainment America Inc.

    In a nutshell
    First comes the idea! "Our director Stig decided he wanted Helios to go down in an epic fashion, with his head being ripped off. Then comes the execution. We had the animation department create the head rip and eye bulge. Then character art modeled some guts and we used some shader tricks to get the ripping effect to happen. The fx department added the blood and the rigging guys put the whole thing together.”

    Creating a usable set of tools in Maya was the first challenge to meet before even beginning to model. “When the studio started, we decided to use Maya and make it our editor. All of our tools are in Maya. We have five technical artists and three tools programmers who are dedicated to creating tools for the artists, designers and animators. Each department has their own toolboxes to maximize workflow. We use Maya’s particle systems, its rigging/animation system and key framer. We’ve created a CGFX shader that utilizes the hypershade and renders in the perspective window. Pretty much any feature that we have on the PS3 renders in Maya and what doesn’t, we have live linked with Maya attributes. Our Programming Team created an entity system in Maya that uses connections and scripting similar to other game engines and editors...

     
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    ... Another primary tool used in developing 'God of War III's models and animation is ZBrush. “We use Maya and ZBrush exclusively. Every character and environment artist on the team has a copy of each. We define modeling and asset creation into 2 categories; object based normal maps and tiled normal maps. I think other studio’s call these micro and macro normal maps. We try and create as many assets as we can in ZBrush using object based normal maps. This allows us to create a very high resolution model, transfer the map to an in-game model that looks like the original asset. We want the assets to look as high resolution as possible.

    Every character is made with this technique, as well as many parts of the environment. If we use a tiled normal map, we try and stay away from using hard edges. We ask the artists to add extra verts and soft edges so light wraps smoothly around the assets edge. We feel this technique defines what a next gen model should look like. For transferring normal and A.O. maps, we use xnormal, ZBrush and Maya. We model our environments on a grid with a designated vertex per meter ratio and keep to a precise texel ratio to maintain a cohesively mapped environment.”

    © Sony Computer Entertainment America Inc.
    © Sony Computer Entertainment America Inc.
     
    © Sony Computer Entertainment America Inc.
    © Sony Computer Entertainment America Inc.

    The lighting system in 'God of War III' is another one of the most noticeable pieces of gorgeous work judging just from the playable builds. “Lighting is very important to the look of 'God of War’s style so it was very important for us to come up with a system that is robust and meets the many needs of the game. We have been working on the lighting since the very start of production, and four years later it’s still something we are tweaking. We wanted to come up with a hybrid system that would meet the demanding needs of the game. For Titan gameplay, we need a fully dynamic lighting solution and for other areas we wanted to use high resolution light maps combined with dynamic lights.”

    Choosing either a forward rendering system or a deferred rendering system would always depend on what the game requires and what the game system is capable of. Fortunately, the devs at Sony Santa Monica are extremely happy to be creating a game on a system as powerful as the PS3 and as a result, the rendering was never a choice of one or the other. “We use a combination of both,” says Feldman. “The dynamic shadow system utilizes a deferred rendering solution and the dynamic lighting system uses a forward rendering solution. From the start we wanted the ability to have a lot of dynamic lights. We did not want frame rate to suffer with each light in the scene."

     
    © Sony Computer Entertainment America Inc.
     

    The programmers were able to create a system that allows the artist to use up to 50 lights per game object while not using the graphics processor. All dynamic lighting is done on the PS3’s SPUs. We separate direct light (dynamic lights and baked shadowing light) from indirect (ambient, skylight, bounce). This allows us to merge baked and dynamic shadows by blocking direct light. We use Turtle for baked lighting. After testing a number of different global illumination renderers, we chose Turtle because of its feature set, lua scripting, its speed and the wonderful support offered by the Turtle guys. Turtle gives us the ability to separate direct lightmaps, or direct vertex lighting from indirect. We use all of its global illumination features including final gather. We use image based lighting or skylights and we have the ability to bake ambient occlusion to maps or verts. We also use Turtle light probes (spherical harmonics) as one of our solutions for lighting the characters.”

    Probably the most impressive feat in the visuals of 'God of War III' are the in-game facial animations. Kratos now looks more grizzly and menacing having him breath heavily and snarl throughout the game intro and well into the main gameplay. “We animate all of Kratos’ facial animation in-house, and several other main characters as well. For some of the secondary characters, we use Image Metrics’ performance capture system to record the voice actor’s performance and apply the pixel-by-pixel facial changes to the 3D model. Once these are implemented, our animators refine the animations further.”

    © Sony Computer Entertainment America Inc.
    © Sony Computer Entertainment America Inc.
     
    © Sony Computer Entertainment America Inc.

    Bruno Velazquez also chimes in on the animations and rigs. “There have been a series of scripts and tools written to facilitate the creation of biped and quadrupeds rigs as well as facial rigs. These however, were only able to get us so far since every character has its own unique rig. No animations are shared between characters and all have unique sets. Due to the complexity of the characters in the God of War series, we were required to come up with solutions and create special rigs for wings, horse legs, tails, goat legs, and a special rig for the Kratos chains among others.”

    Now, does Ken Feldman feel like there is an idea that could have been utilized in 'God of War III? “I tried unsuccessfully to convince Stig to make 'God of War III' a first-person shooter. Kratos could have some truly badass huge weapons that rip gods to shreds. Unfortunately he didn’t see the genius in the idea.” There’s always spin-offs.

     

    Related links:
    God of War III
    Sony Playstation 3
    Turtle
    Maya

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