CGSociety :: Game Production Focus
21 January 2010, by Peter Rizkalla
The first Left 4 Dead exhibited gorgeous facial animations and stunning character designs. This time around Valve has pushed Left 4 Dead even further. I talked with a few of the devs at Valve to learn
more about the design direction they wanted to push with Left 4 Dead 2.
We have Jeremy Bennett on characters, Randy Lundeen on environments and our Valve PR guy Doug Lombardi on congas.
In any game, movie or animation that exudes good design, it is likely that questions like "What kind of ideas didn't make it to the final version?"
will arise. The main idea behind Left 4 Dead 2 was to implement those good design ideas that didn't make it into the first game and expand upon them with even newer ideas.
"We had a lot of ideas while working
on the original Left 4 Dead that didn't make it into the game for one reason or another and the team was excited to continue the franchise by putting these ideas
into a sequel," said Bennett. "As with any sequel, we wanted Left 4 Dead 2 to expand the universe
of the franchise, create a fresh world design, introduce new characters and creatures, explore new game play scenarios and introduce new tech features."
Visually, Left 4 Dead 2 had to differentiate itself from the first title. Largely, this would mean that the locale and environments had to be
fresh. "Gone are the back alleys of Philadelphia and the Pennsylvania countryside found in Left 4 Dead," says Lundeen.
"In Left 4 Dead 2, the players find themselves in the bayous, plantation ruins and parched cemeteries of the Deep South.
We wanted to convey the feeling of sweat and mosquitoes,
of Jack Daniels and flat pop. Naturally, we sent some team members on scouting trips to the area to gather photo
reference for texture and environment creation."
"The Deep South is rich in game play environments and charting the Survivors' path across these locales proved entertaining and artistically satisfying. Who wouldn't want to fight the hordes in a ruined
Plantation House, an old Sugar Refinery during a thunderstorm or the iconic setting of the French Quarter?
With the Deep South theme, New Orleans was an obvious choice for one of the campaigns."
Much like the edifices and alcoves of the actual Deep South, Left 4 Dead 2's environments had to have the same feel and communicate that feel to the player.
"Architecturally, we identified specific elements to create a formula for our vision of the city. These elements included the high ceilings necessary to dissipate the intense heat of the region and the
classic French Quarter balconies. The roof lines are dominated by gabled or hipped styles and most buildings in the area are only two or three stories tall."
"On our scouting trips, we found a plethora of small courtyards and narrow walkways between buildings that were not only a visually interesting feature of the area, but also provided great opportunities to
spawn in 'infecteds' to surprise and ambush the survivors in the game."
Giving environments the polish they need to bring everything together consisted of some out-of-the-box methods.
Things like flowing water and thunderstorms needed to be cleaned up, made believable and, of course, be done within the time that the dev team was given.
"In particular, the 'Swamp Fever' campaign required a highly optimized water rendering method to really sell the environment and still work within our technical constraints."
"Also, in order to help guide players through the swamps, we wanted to have the water generally flow down
the path to the end of the map in a way that was subtle enough to be natural, but clear enough to cue
the players to their intended route.
We implemented a new water shader that could have a unique flow direction and water speed at every point on the water surface. We used Houdini to generate flow maps
offline by first painting 2D flow directions manually. Another campaign that needed some additional effects work was
"In this campaign, we wanted to create the sensation of being caught in a thunderstorm with driving rain. The particle effects
of the storm are made up of several thousand individual drops, impacts, mist
sprites, and screen effects. After the storm effects went into the game, we soon realized that the motionless trees were breaking the illusion of the powerful storm that we had worked so hard to create."
"To combat this, we added the ability to procedurally deform our tree models in a shader. Based on wind direction and strength, we use a low-frequency back-and-forth swaying motion combined with
higher-frequency motion to shake thinner branches and leaves. This procedural approach was significantly faster to implement than rigging all of our tree models for traditional skinned animation, which
was especially important given our
With the new Left 4 Dead comes a new cast of survivors. These new survivors had to feel like they were a part of this new setting, like they were all supposed to be in that particular part of America and that there is a reason why they are all still alive
after fighting hoards of undead.
"When designing the new Survivors for Left 4 Dead 2, many ideas were explored, with some of the potential characters better suited to a world ravaged by a global pandemic than others, but all with
characteristics that would have made them interesting to be around," said Bennett.
"For each suggested character, we would evaluate the designs with some key questions like 'Why would that particular person have survived?' "What is it about their background, career choices etc. that
has left them to mop up?' If the character in question was a feisty barmaid or used car salesman, 'why would they still be knee deep in gore and reaching for the ammo?'
Of the many suggested
characters, we settled on a group of
four who seemed the most interesting to us individually and as
Coach is the big fella with the physical attributes that would suit
a bar brawl as much as firing up a chainsaw and cutting swaths through the infected masses.
Ellis is someone we imagined we would find in the Deep South,
a local not too concerned with what is happening in the grand scheme of things and therefore making the most of his new messy world.
Nick, our slightly dodgy 'river boat gambler' type, struck a believable cord as soon as he was pinned up on the office wall.
A person like that has 'survivor' written all over him and the fiction we
could attach to his persona seemed endless. Hey, why not dress in an expensive suit and wear pocket loads of bling?
It's not as if anyone needs it and if you look slick while wielding
a pump action
shotgun, well, all the better.
Our lone female, Rochelle, was a bit harder to pin down.
She needed to be feminine and smart, yet capable of getting the job done just as well as the boys. We imagined someone from further north in the
U.S. who may have been caught out while working down south, someone who adapts well, is organized
and possesses the necessary temperament to cope with the spreading infection."
In addition to the traditional Left 4 Dead"Special Infected" zombies like the Boomer, Smoker and Hunter; Left 4 Dead 2 introduces three new special infected zombie designs, one of which is the Jockey
which is a short, annoying and hard to hit zombie that mounts a survivor and steers them away from the other survivors or steers them into a hazard.
Another of the new Special Infected with an interesting design
is the Charger. "The Charger, by contrast, is massive and unexpectedly quick on his feet. His bold asymmetrical bulk belies the ability to
deal a serious blow when encountered in exposed spaces. This coupled with a distinctive vocal signature makes for a fast moving sledgehammer that will leave you with a health-depleting hangover if you
are unfortunately distracted."
The design of Left 4 Dead 2 not only surpasses the first game of the series but also sets up a standard to be met by any other studio of game developers that attempt to release a series of titles yearly.
"Left 4 Dead 2 turned out to be a fun exciting project for the team and company. In the end, we were able to accomplish our ambitious development goals and expanded the universe of the franchise, creating fresh new settings, introducing new characters and creatures, adding new game play scenarios and introducing new tech features all in just one year."
Companies like EA Sports and 2K
should take design lessons from Valve
on this one.
Some of the common zombies have also been given different designs which also provide them with game altering attributes. "You are now confronted with bullet resistant Riot Cops, Work Men with ear
protection who don't respond to pipe bomb beeps, Mud Men that quickly sneak-up on you in the swamp with a disturbing all-fours shamble, fire-resistant Hazmat suit clad infected zombies and zombie circus
clowns whose squeaky shoes draw an unfriendly crowd of common infected."
Surprisingly, one of the most outstanding visual qualities of Left 4 Dead 2 is how the zombies are wounded by the attacks of the survivors. "We figured that since most players spend a majority of their
time shooting the common infected, we should spend time trying to amplify the visual impact of this action. In Left 4 Dead, we provided only the ability to remove limbs with blood decals for bullet
In Left 4 Dead 2, there are 43 unique ways to damage the infected, from gunfire to melee weapons to explosive damage. To create the appearance of an individual wound, they procedurally cull an ellipsoid
around the wound location using a pixel shader, creating a cavity for an underlying would model to fit into. Beyond just location-specific wound models, weapon-specific damage models were also enabled,
due to the different characteristics of certain weapons.
For example, the Sniper rifle headshot explodes the head and the axe creates slash type wounds when it strikes across meaty areas of the body. The resulting carnage leaves players with a more realistic
impression of the damage dealt by the game's arsenal of weapons. For an even greater idea of this particular effect, players should try shooting
a zombie with a shotgun. Artistically It's pretty,
aesthetically It's not so pretty.