Developers Diary: Bringing Call of Duty: Roads to Victory to the PSP


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.