The Last of Us Part II Developer Breaks Down Its Amazing Breathing System

I'm only not using "unreal" because this is definitely real and the product of so many brilliant people's hard work.

A sound designer on The Last of Us Part II has extensively explained the game’s… nearly unfathomably intricate breathing system.

Beau Anthony Jimenez posted two Twitter threads on July 18 elaborating on the game’s subtle, but powerful breathing system. It’s not one of the most immediately noticeable features in the game — and that’s what makes it so incredible, especially given the amount of work that has clearly gone into this.

The first thread establishes the breathing system, introducing the system’s integral concepts of “murmuration” and “heart rate.”

Jimenez states that murmuration is, “a looping sound on a character. It’s the lowest priority sound possible, so any sound that triggers (from melee, anim, script or code) will stomp it. After the one-off plays out, the loop will return where it left off, creating a seamlessness in the breath.” It’s the sound under all other sounds. For Ellie and Abby, it’s their breathing; for the Clickers, it’s their shrieking and clicking.

Then there’s heart rate, which is a number ranging from 0.0 to 1.0, with 0.0 signaling a character’s most relaxed state while 1.0 signaling a character’s most exerted state. This heart rate wasn’t assigned to just playable characters like Ellie and Abby, but also partners like Dina, Jesse, Lev, Manny, and even the Infected, dogs, and human NPCs. Each heart rate has a different “heart rate state” that changes depending on various factors like enemy proximity and enemy attacks.

“As an example, if Ellie is sprinting in ambient tension, her Heart Rate state is ‘ambient-high,'” writes Jimenez in the first thread. “When you let go of sprint, (NOT sprinting) it becomes ‘ambient-low’. With this, I’m able to determine how long it takes the Heart Rate number to go up/down from different states, letting me choose how long I want to hear Ellie’s exhausted breaths peter out or how long it takes Ellie to sound worn-out after sprinting for a period of time.”

While murmuration is constant, the developers have overridden it for custom story beats, like Ellie squeezing through a tight space before getting attacked, or a character being particularly exhausted after sustaining a painful injury in the narrative. As Jimenez writes, this system “helps you empathize with their story by communicating how they’re feeling. Breath can be an excellent conveyor of emotion!”

While Jimenez goes on to highlight the especially impressive open/closed mouth stealth breathing system, my favorite part of the first thread has to be the explanation of Abby’s vertigo. Abby has acrophobia, an extreme fear of heights, and this character detail was implemented in even the smallest, most subtle touches of gameplay. While playing, I definitely noticed how the camera would pan to accentuate Abby’s fear of heights as she approached ledges; however, I didn’t quite notice the degrees to which her breathing speeds up and how significantly her body language changes. It’s incredible to witness it.

The second thread is more about reflecting the audio design of the breathing system through the visuals — namely, aspects like Abby’s body language (which you can see the range of in the clip above) or Ellie’s facial animations depending on her heart rate state. I feel like Jimenez encapsulates the system best when he writes, “It’s similar to lighting, in that it’s hard to notice, but undoubtedly resonates with the player emotionally & creates a palpable tension in the gameplay.”

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As Jimenez finishes the threads by thanking multiple programmers, animators, dialogue designers, developers, and the voice actors, it’s clear that the “magic” Jimenez references in the very first tweet isn’t quite magic. It’s the product of extremely hard work from countless developers who collaborated over many years.

It’s also a notion we can, and should, acknowledge but not romanticize, especially when it’s been well-reported that Naughty Dog employees were made to crunch to extreme degrees while developing The Last of Us Part II. We can recognize the hard work, amazing talent, and attention to detail on display here while demanding an industry whose workers make innovations like this to let them do so without sacrificing their livelihoods. Crunch is not required to make great art.

Jimenez isn’t the only developer who has tweeted threads elaborating on the attention to detail in The Last of Us Part II. In terms of sound, earlier in July, dialogue coordinator Grayson Stone also made a Twitter thread breaking down the communication system of the Seraphites, one of the game’s enemy factions that communicates in the field through whistles rather than words.

The Last of Us Part II is out now for PlayStation 4. For more of our extensive coverage on the game (since several Fanbyte staffers are pretty big and emotional fans), be sure to read Kenneth Shepard’s twopart review, as well as our numerous guides, news stories, and opinion pieces.