If there's one thing that's impossible to ignore about Horizon Zero Dawn, it's the gigantic machines you go head-to-head with. All of them resemble different wildlife, from dinosaurs to crocodiles to hyenas.  Guerrilla Games spent a lot of time thinking about various features of these mechanical beasts, from their role in the game's ecosystem to their weaknesses and values. While in Amsterdam, the team gave insight into the intricate process of bringing these intriguing creatures to life by showing us how the Shellwalker came to be.

Taking Real-World Inspiration

Guerrilla tries to look for inspiration in nature for all its designs, using recognizable wildlife to form its robotic creatures.  "We go for that...that there is a recognizable element in there," says lead designer Dennis Zopfi. "We try to twist it a little bit, so that there's something new to it." This all ties into giving you familiarity before stepping into battle. "The reason for that is so that you expect certain behaviors and movements, so it's all about readability," explains managing director Herman Hulst. "The combat encounters need to be fluid and easy to read."

For the Shellwalker in particular, the team looked at various pictures of the hermit crab, focusing on how it shields itself and uses its claws for protection. The Shellwalker is part of the transport class of machines within Horizon's unique ecosystem. Guerrilla studied hermit crab movements, especially how they looked and functioned in groups. They rarely travel alone, and the lowest amount you'd usually encounter at one time would be three.

Because the Shellwalker is part of the transport class, it needed something to cart; this led to the addition of the Shellwalker's precious box on its back. Moving boxes is all that matters to the Shellwalker; this is the role it's programmed to perform and the creature will do everything in its power to ensure it doesn't leave its box behind and completes the task at hand. Once Guerrilla gets some ideas down, it has designers build the machine as if it could actually be constructed. Yes, actual engineers are on staff who do this. This also means designing all its behaviors; the team especially spent a lot of time deciding on how the Shellwalker would handle the boxes. From there, it's deciding on how large certain elements, such as the claw or box, should be in the world.

Bringing Robots To Life

Guerrilla Games has a team of six that do nothing but work on animations for the machines in the game. Visualizing these robots is one thing, but it is a whole other task to make sure they work within the game. "We need to make sure that things move in a way that makes sense, but also have enough clearance so that the things that need to happen in gameplay can," says principle animator Richard Oud.

For the Shellwalker, one of the things they needed to test and get right was the length of its arms to be able to pick up crates and put them on their head or strike the player from the side. The Shellwalker design had bulky arms, which made animating them a challenge, because there wasn't always room to convey as much as they wanted. The animators made some adjustments, such as making the eye units move in and out, instead of just sitting there on top of the Shellwalker. "It gave it a little more of a robotic feel to it," Oud says.

Most of the time during the animation phrase, the team starts discovering what's fun and interesting about each machine. "Every robot has its moment where you find out its personality," Oud says. "For the Shellwalker, it was the first time he puts the crate on his head. His only obsession is protecting his cargo. When we did the first animation, that's the moment it started clicking with the whole entire character."

While the box certainly stands out, the Shellwalker has 150 unique animations to make him feel alive and react to various things that happen in the heat of battle. For instance, even if you shoot off the cargo clamp, he'll use his claw to secure his crate, giving him one less weapon to use against you. If you kill him and shoot off his precious cargo without destroying it, there's loot awaiting you. However, you never know what or how much is inside, making it a gamble.

To make these robots feel even more in tune with the world, their behavior will change depending on which other machines are or aren't around. For instance, if Watchers aren't around to alert of nearby danger, another machine, such as a Grazer, takes on patrolling. Grazers, which are usually peaceful animals, can also have one of its members turn into an alpha male if it gets angry. "These roles are layers of complexity on top of the generic group behavior," Hulst says. The components they have also determine their behavior and help players strategize how to take down these mammoths. Machines always have some type of risk/reward, whether it's loot or a weapon you can shoot off. Guerrilla also focused on getting the destructibility of these machines just right, so as you shoot off more and more components, robots reflect that and start to look different.

Finding The Right Voices

Sound can be make or break any game, so Guerrilla is doing all that it can to capitalize on this in Horizon Zero Dawn. Different machines all have memorable sounds that you can recognize from afar, such as the piercing lasers coming from Scrappers. "It was really hard at first to find a balance between machine and animalistic at first," says senior sound designer Anton Woldhek. "If you went too far animalistic, they wouldn't really seem like machines anymore. And if you went too far robotic you lost the emotional impact. It was a lot of experimenting and finding out what worked emotionally as well as rationally in this world."

For instance, the Shellwalker, every so often makes a sound that conveys his state, while his machine-like elements come in the sound of how he walks and how he picks things up. As soon as you start to get in his way, he pounds his fist angry and lets out a terrifying mechanical shriek. Every robot has 200-300 unique sounds and then there's another 150 sounds that are shared between the different machines. For instance, when they're walking on different materials you get different sounds and different A.I. states, such as suspicion, also bring out different noises. "There is a lot of inspiration from animals," Woldhek says. "Sometimes it comes from directly how they sound, so you can use the recording and change it. And sometimes you take information from that. For example, if there was a robot that could howl. You might not modify a howl, but analyze the recording and say this is the pitch is goes up and down by and then recreate that sound using something completely different."

Finding machines and how they act is part of the fun for Horizon, so we don't want to spoil too much about the sounds or their creation. However, it sure seems like Guerrilla shares plenty of our excitement about these robotic creatures and is putting a lot of time into making sure they function in the world in interesting ways. What do you think of the machines you've seen so far?

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