Aloy's inaugural adventure struck a chord with many players. But along with the mechanical dinosaurs and visual prowess that made Horizon: Zero Dawn a smash hit, there were also some intricate development that handles the anthropomorphic beasts, their behaviour and movement throughout the world.
The behavioural models of Horizon is the focus of the latest AI and Games episode, a YouTube series that breaks down the AI in various video games. All in all, there's 28 separate machines (or robo-animals) that have their own hierarchies, individual and pack behaviours.
The video isn't purely theoretical, though: it's based off information presented by Guerrilla Games developers at three conferences across 2017 and 2018, which covered how the developers adopted or created the AI, navigation, sensor and animation systems for Horizon. Some of the techniques and base principles have been used by Guerilla Games as far back as Killzone 2, although there's a ton of improvements and tweaks that have been implemented over time.
One highlight in particular is The Collective, which is the name for Horizon's overarching supergroup system that monitors all agents and machines, monitoring and coordinating the movement of individual machines, whether they're by themselves or in groups, whether a particular machine should be spawned into the world or join a particular group of machines, and more.
There's a full article on the AI and Games website that covers the hierarchy and behaviours, and it's well worth a read. Breaking down these kind of behaviours helps provide a great insight into development that people often take for granted, or understand little of.