Developers’ Diary: Bringing Call of Duty: Roads to Victory to the PSP
By Alex Pantelias – Producer

"Call of Duty: Roads to Victory is unlike any game we have created in the past"

“Call of Duty” games are synonymous with intense action and cinematic presentation.  “Call of Duty” features expansive, detailed environments, a whole squad of allied soldiers, and hordes of Nazi enemies on screen in intense firefights.  The sound treatment and quality special effects are calling cards for the franchise.  The game brings the epic, cinematic feel of WWII to the PC and console screens, letting the player become a part of the vast landscape, fighting the good fight.  Just how does one take this historic franchise and build it for the PSP?

TOPICS:

• Audio/Sound/Music

• Art/Levels

• Design/Gameplay

Audio/Sound/Music
Drew Cady/Mark Yeend – Sound Engineers

Call of Duty: Roads to Victory is unlike any game we have created in the past. The audio is a big part of the game. Since we have a very limited memory budget we had to expand on how the audio was played to offer the variety we needed. Below is a description of how I went about all audio programming.

Audio has always been a huge part of the Call Of Duty franchise.  The bar was set really high by the awesome work of previous sound teams.  We knew we would have to push the limits of the PSP to achieve the variety, depth and sheer number of sounds we needed.

One huge component in making the game feel like WWII was ambient sounds.  We needed the background sound effects to be dynamic and evolve, pulling the player into the game. To offer more variety and flexibility I created a preset system, reusing a limited number of explosion and gunfire sounds with varying pitch and timing, instead of an ambient sound stream that would repeat.  This allowed us to change the behavior of the ambient sounds dynamically, based on player location and game states from level designers.  That's how we created tension, varied the emotional intensity, and kept things sounding fresh.  For instance, we could start a level with the war sounding distant, favoring long spaces between relatively quiet sounds.  Then, when the war started increasing we could switch to a new ambient sound preset that used more sounds, louder sounds, and triggered them more often.  When it all came together, we saved a ton of space and created an exciting, evolving, and unpredictable soundscape of war.

Because of size constraints, reusing sounds was also critical, since we were faced with literally hundreds of animations.  Through meticulous scripting, we would vary the timing, pitch and volume of our Foley sound effects (crouching, mantling, reloading, throwing, etc.) for each character type.  The result was the illusion of variety, even though our shared sound set was quite small.  We used similar techniques for bullet-impact sounds, bullet whiz-by sounds, grenades, and many other cases.

One direct emotional hook was in the voice over.  One hallmark of the Call of Duty series is almost constant shouting, groans, and encouragement and direction from NPCs.  Our sound team worked with the engineers to develop a "chatter system" which, again, used a small palette of voice sounds to react to a carefully defined set of AI conditions.  We created another illusion of vast variety by duplicating the chatter script in every level, but filling in the script with unique voice files, so that we would not hear the same voice in any consecutive levels. 

The other, more subliminal emotional hook (and trademark of other Call of Duty games) was incredible music.  Following closely the style and usage set forth by previous Call of Duty games, our talented staff composer, Noel Gabriel, created a score for key moments in each level.  We worked closely with level designers to trigger these pieces, and the results are very effective. 

Art/Levels
Jason Piel – Lead Artist

Call of Duty: Roads to Victory was a tough game to fit onto the PSP screen.  It was a difficult balancing act to fit all the textures at a good quality into the level and keep the textures palletized, so that they would fit into the PSP Level cache. 

FX –

Our effects got the most attention, as these are the elements that keep the level active and help convince the player that a war is going on around them.  We used the best quality and biggest textures, but kept our particles at lower rates.  Because of the PSP's smaller screen size, we had to exaggerate the effects to give greater impact.  Because the effects were also paired with sounds, they could get expensive, so we chose ambient effects wisely, and spread them in multiple locations in a level.  Dynamic lights in the muzzle flashes help identify small camouflaged enemies on the PSP screen.

Characters/Animation-

All characters shared the same skeleton (under 20 bones) and animations.  All of our thousands of animations went into the PSP's volatile memory.  This let us create more variety and realism in character acting, which is very important when portraying convincing AI in a war situation.

Levels -

For Call of Duty: Roads to Victory we spent a lot of time researching locations and balancing the game play in our unique levels.  Classic Call of Duty Multiplayer levels were downsized to accommodate 2-6 player battles and keep the action moving.  Fog helped to mask long viewing distances, and helped to create the feeling of war.  Lots of cells and portals helped to draw only what was needed.  The skybox got a lot of attention to help set the mood and keep the level alive.

We spent a lot of time tightening our texture mapping to counter the necessary mip-mapping which was a big issue in a first person game where you hug walls, crawl along the terrain, etc.  Lighting creates both dramatic settings, and helps the player locate targets and direct them to areas of interest.  Large props and landmarks helped us create unique settings and memorable moments.  A streamlined collision system was used to simplify the level for the AI and allowed us to mark surfaces as metal, wood, etc, for the sounds of footsteps and bullet hits.

Textures -

We based our texture resolution on the scale of a full body trooper character as seen by the player.  So first person weapons and vehicles needed larger images to match this scale, smaller objects and terrain could use smaller images.  Most textures were palletized, and had no alpha information. We have a unique texture blending shader that allows us to help hide the repeating terrain and create more natural looking settings.

Design/Gameplay
Chris Brocket / Eric Gingrich – Designers

The biggest issue with FPS games on the PSP always seems to be the controls.  The absence of a second analogue stick makes FPS controls a bit tricky.  We focused a large portion of our design time on testing various control layouts with the goal of whittling all the possibilities down to four versatile schemes.  The problem then was, which one should be the default scheme? Everyone had different opinions on which scheme was the best. After a good deal of focus testing, the final default control scheme was one that allowed manual targeting (free-look), but still had an element of target assist built in. The scheme allowed the player to strafe, use cover, look around, and still be able to shoot moving enemies.

We didn’t want the game to become too easy because of auto-target, so we made it tunable per gun.  Machine guns have a short auto-target range, rifles have a further range, and scoped weapons have the longest range.  Within these categories, we used the auto-target range to give certain guns a little personality and strategy. 

To further balance game play, we made shooting from the hip and auto-target less accurate than ADS (Aim Down Sights) also called Iron Sights.  A player who could manage to aim accurately in ADS could benefit from increased range and accuracy.  In this manner, players ended up using auto-target only when they were overwhelmed by enemies up close, or had trouble aiming at moving/charging enemies.  Players would conversely use ADS to pick off entrenched targets at range (while behind cover).  Of course, the player also has the ability to turn off auto-target if they are yearning for a truly hardcore experience.

Call of Duty is know for putting multiple enemies and allies on the screen at the same time. Not only are there enemies, there are also allies fighting along side the player. We had to come up with creative solutions to craft an experience that felt and looked a lot bigger than the sum of its parts.

We did this in a variety of ways.  Whenever an ally is killed during an engagement, we often replace him with another ally coming up from behind the player to take his place in the battle. This simple trick works surprisingly well but requires careful level design and planning to support it. In terms of presentation of enemies, we tried to always surprise the player and keep up a hectic and frenetic pace.  For instance, in one level we had a truck pull away and reveal Nazis hiding behind it.  In other levels we designed breakable walls, destructible cover, and room-to-room battles that all presented good enemy hiding spots.  This keeps the player off balance, as they never know where the next threat might be coming from. It also enforces a general rule of a Call of Duty game:  Use cover when advancing!

We also used special effects to our advantage.  Fighting down an occupied street is fun, but if you add fighter planes flying overhead, walls crumbling from mortar hits, explosions happening around you in the street (with screen-shake), and vehicles on fire…the experience becomes much more intense.  This was our main design goal:  Keep the player on the edge of their seat.  The end result is that Call of Duty: Roads to Victory portrays a chaotic and intense battlefield in which the players feels they are fighting an army alongside their squadmates.

The design team absolutely wanted to nail the intensity because most PSP shooters tend to skew more towards stealth/distance firefights (take enemies out quietly, one at a time).  We wanted to be the first PSP shooter that put the player right in the thick of battle, with their heart pounding in their chest.  Doing this on the PSP platform took a lot of work and strict memory/size budgets, but we feel the payoff is well worth it.

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