Editing Machines (Horizon) (section)

=== Animation and audio design ===
To animate and telegraph the machines realistically, the development team took courses in animal and creature animation and consulted Dr. Stuart Sumida, an anatomical consultant for film and theme parks.<ref name="LivingCreatures" /> Lead animator Richard Oud noted that the team frequently used viral videos of bizarre animal behaviour to inspire unique attack patterns. For example, the Bellowback's fluid-flinging attack was inspired by a real-world fight between an [[emu]] and a [[kangaroo]]; animators noticed the emu curled its neck like a baseball pitcher winding up a throw, which fit the machine perfectly. The burrowing Rockbreaker's movements were based on footage of [[sea lion]]s fighting to portray a mix of heaviness and agility, while the [[bear]]-like Frostclaw's distinct tumbling attacks were inspired by the feisty rolling of [[red panda]]s.<ref name="GRAnimals" /> Animation was deeply tied to machine status; for example, the [[Hermit crab]]-like Shellwalker has 150 unique animations, and its behaviour changes based on its components. If the player shoots off its cargo clamp, it will use its claw to manually hold onto its crate, sacrificing a weapon to save its resource.<ref name="GIMachines" />

[[File:Horus Concept Art for Horizon Forbidden West Burning Shores.jpg|thumb|left|Concept art of a Horus, which were designed to visually demonstrate the apocalyptic destruction of the Old World. Senior Art Director Misja Baas said that their design allowed the developers to "drape the machine on the landscape and make it look very dynamic", serving as environmental storytelling that captures the last moments of life on Earth.<ref name="HorusBoss" />|alt=A large mechanical machine with multiple long legs and the partially destroyed Hollywood Sign]]

While Horus units appear as dormant landmarks in ''Zero Dawn'' and ''Forbidden West'', a fully operational unit was developed to serve as the final boss encounter in ''Burning Shores''. The animation team had to navigate massive technical complexity, as the Horus features over 1,240 articulation joints, which was a massive increase compared to the base game's most complex machine, the Slitherfang, which capped at 240. To reflect its nature as an ancient weapon reanimated by an external force, its movements were themed around a "shambling zombie"; instead of powering through smoothly, it was animated to lurch, struggle, and claw its way forward uncoordinatedly.<ref name="HorusBoss" />

Sound designers balanced robotic and animalistic noises to create an "emotional impact", an approach the audio team dubbed "natural-fiction".<ref name="NaturalFiction" /> To ensure the machines felt grounded in reality, the audio team avoided relying exclusively on synthetic noises, instead anchoring the digital samples by layering them with organic, real-world animal recordings.<ref name="GuerillaAudioInterview" /> By dynamically blending synthetic, electronic creaks with these organic vocalisations, they gave most machines between 200 and 300 unique sounds, with another 150 shared across types.<ref name="GIMachines" /> To guide these vocalisations, the designers [[anthropomorphism|anthropomorphised]] the machines with distinct personalities; for example, the Shell-Walker's audio was designed to mimic a "grumpy crab-guy" annoyed by his work, while the Watcher was modelled after a "crazy [[Chihuahua (dog breed)|Chihuahua]]".<ref name="NaturalFiction" /> However, rather than simply pitch-shifting the recordings to fit these personalities, the team sometimes analysed the acoustic data of a real animal's call, such as its pitch modulation, and applied that data to recreate the exact auditory pattern with entirely synthetic sources.<ref name="GIMachines" />

The team used audio to further distinguish the origins of the different machine classes. When designing the futuristic terraforming machines, sound designer Pinar Temiz intentionally avoided using traditional metal scraping noises because listening to them caused her physical discomfort. She used the lore of exotic, futuristic alloys to justify this limitation, resulting in a unique sonic profile that relied heavily on animalistic cues.<ref name="NaturalFiction" /> To ground the machines in the world, the audio team created unique [[Foley (filmmaking)|Foley]] for machines walking across different terrains to convey their weight.<ref name="GIMachines" /> The underground environments that manufacture the machines, known as Cauldrons, were similarly designed to contrast the natural world. Because humans had never set foot in them, their audio was engineered to sound like loud, early [[Industrial Revolution]] factories lacking acoustic protection, mixed with slick, alien synthesisers.<ref name="GuerillaAudioInterview" /> Conversely, the ancient Old World military machines lack vocalisations entirely, instead relying on heavy, traditional metallic clanks to communicate that they were built using older, recognisable human technology.<ref name="NaturalFiction" />

To ensure the hundreds of unique sounds did not overwhelm the player, Principal Sound Designer Anton Woldhek and programmer Andreas Varga built a highly flexible, systemic audio engine called Guerrilla Dynamic Audio (GuDA). Rather than using hard-coded audio triggers, the engine actively monitors the environment and dynamically mixes the machine sounds, weather effects, and the musical score so they do not overlap and clash. This system actively reacts to variables such as the player's current biome, the number of enemies present, and the shifting "emotional" states of the machines,<ref name="GuerillaAudioInterview"/> altering a machine's vocalisations dynamically based on whether it is suspicious or aggressive.<ref name="GIMachines"/> To upgrade the audio for the new machines in ''Forbidden West'', the developers designed highly specific audio cues that allow the player to predict a machine's behaviour, such as distinct sounds for idling, alerting others, or initiating attacks. These details were further amplified by the [[PlayStation 5]]'s 3D audio capabilities to provide the player with greater situational awareness.<ref name="HFWReBuilding" />