Why Horizon Forbidden West: Burning Shores’ Hugs Are a Secret Technical Marvel

When Guerilla Games released the trailer for Burning Shores, the new expansion for Horizon Forbidden West, developers from other studios quickly noticed a moment that might not have gone unnoticed by other studios. .

The 0:45 hug is a technical flex like “YOU HAVE NO IDEA” https://t.co/h0dmivkOpl

— Zalavier Nelson Jr. (@WritNelson) April 19, 2023

“The 0:45 hug is a technical flex that you don’t think about,” wrote Xalavier Nelson Jr, head of Strange Scaffold. He echoed the replies from many other developers and fans and everyone was shocked to see why we made it. As such, he is rarely seen in-game with two characters hugging each other. Ultimately, it turned out to be very difficult for developers to do this while still looking normal and believable. Yet Guerrilla has been giving Aloy his friends warm hugs since Zero Dawn.

So how does Guerrilla achieve this technical feat? I admit that I was pleasantly surprised to find out. Wood says Aloy loves hugs, so Guerrillas are used to the extreme challenges required to make all these hugs happen… made significant progress.

WARNING: Although the text of this article contains no spoilers, the video content in this article shows cutscenes from the endings of Horizon: Forbidden West and the Burning Shores DLC. Please view at your own risk.

hug resolution

Guerrilla and Other Developers Face Challenges Begin with Motion Capture [mocap] Suits are used to record movements and facial expressions and have become a standard sight in the gaming industry. The motion capture suit works through sensors scattered throughout the body, which software can track and translate into recorded movements. But when his two actors in motion capture suits hug, their bodies are pressed against each other, and so are the sensors. As a result, a full half of each person’s sensors disappear from the software’s view.

This means a human would have to manually “solve” the captured motion data, and the software would have to know where the sensor should be at any given time, Wood explains. In this case, all missing sensors must be worked out for the duration of the hug. This is a time-consuming task that machine learning may actually speed up in the future, but for now it has to be done manually in-house or outsourced to another studio, Wood said. said. The animator cannot touch the scene until this is done.

Once that is resolved, a second problem arises. Motion Her Capture Her suit is basically just a flashy second skin for her, but the characters you hug in-game are usually clothed.

“For example, if you look at things like the armor that Aloy is using, all that stuff is not considered in motion capture,” he says. “I mean, even if the data is solved, all you get is the foundation. So the whole animation from that point onwards has to be addressed so that it doesn’t intersect with the cloth the person is wearing, hugging.”

If you’ve ever played a Horizon game, you can imagine that this is no easy task. Aloy and his friends all wear elaborate and detailed costumes, often with many embellishments and other elements sticking out, and Aloy himself has multiple different costumes, all of which are must be considered.

capillary physics problem

After that, the problems never stop. As Oud noted, Horizon’s motion capture actors typically wear head mounts to track facial expressions and provide animators with data to work with. However, the animators must animate the character’s facial expressions entirely by hand, as they cannot wear giant head mounts when hugging. According to Oud, this means that all three of his different endings in Burning Shores were fully keyframed his animation because of this.

More problems arise when animators are on set. Oud explains that one of his problems is that scenes with hugs actually require the animation to run at a higher frame rate. Otherwise it will look silly or wrong.

“You want to really feel the connection between people, which means you have to run the animation at a really high frame rate or a high position rate, otherwise you’re basically going to have a little jitter,” says Oud. says Mr. “[T]The engine actually interpolates between frames. Usually you actually animate at 30 frames per second, but the game he’s running at 60 or 120 frames per second and in this case the missing frames are usually just calculated by the PlayStation is.

“And if the refresh rate is too low, things can really start to shake. And it’s basically like there’s still a little intersection or you’re actually reaching for someone and grabbing them steadily.” Because it doesn’t feel it means it won’t look right. will be played at

Finally, there’s Aloy’s hair, a gorgeous, flowing red elephant in the room.

According to Oud, in Horizon: Zero Dawn and Forbidden West, Guerrilla essentially has eight different hair “poses” to accommodate the majority of Aloy’s movement and speed. I was using a hair setup. Her hair is made up of many “collision capsules”, which for non-animators can be imagined as a mass of tubes that are attracted to her in one of the poses it is set in and then released once the pose is complete. I can. Natural hair with movement.

But in Burning Shores, her hair got a few upgrades. The team wanted to push Aloy’s hair further, but it wasn’t until near the end of the project when the majority of the gameplay was complete that the idea to do so came up. However, since cinematics usually happen towards the end of a project, we were able to implement Aloy’s new hair features in cutscenes like Seika and Aloy’s hug.

“The way Zero Dawn and Forbidden West worked was that clash. The hair clash was locked, right?” Oud explains. “There wasn’t really a way to override it unless you actually changed the costume and put the hair in a new pose so that the hair doesn’t actually intersect the armor.”

To solve this problem, Guerrilla introduced what Wood calls a “movable collider.” Oud explained to me: If Aloy’s hair is made up of bundles of small tubes, there is a law of physics that makes them bounce off each other when they come in contact with another tube. But they cannot move by themselves. So the team introduced new collision capsules that react specifically to them, but are only available in cinematics, wrapped around Seika’s arm. The result was a hug in which the hair seemed to move naturally as the arm passed through it, rather than awkwardly sitting on top of it or being weirdly cropped.

“In this case, when Seyka reaches into her hair and starts walking through it, we actually animate a capsule that looks like a moving collider,” he says. “We actually animate at the same speed and same position as the arm is actually moving. This reacts to the hair and moves her arm away from the hair to make room for the arm to hug.” It looks like it’s going.

This change is made possible thanks to Jolt Physics, the open-source physics engine that Guerrilla switched to for Forbidden West. Among many other benefits, you can have more objects with real physics in a given scene, such as allowing a lot of Aloy’s hair.

“Static worlds are great, but when things really start moving, they actually have AI and they react to physical objects, the more it does, the more computer applications in this case do. More calculations need to be done, less calculations need to be done, basically at a given point in time they can be displayed on the screen,” says Wood. “That’s also one of the reasons why we’ve really only chosen his PS5 only in this case. It’s much more visual fidelity and more objects on the screen than we were able to achieve with the PS4. I was able to.”

engineering intimacy

Issues like the one Oud describes affect all kinds of intimate interactions characters have, not just hugs. This is one reason why many games don’t often show the simple act of one character passing an object to another. The rules, physics, and animations of detaching 3D objects from one character and attaching them to another all look smooth and natural, but are a “technical nightmare,” says Oud.

Kisses run into similar problems to this and hugs, or basically when two characters need to touch and then move in tandem in a way that normal people do. It’s cheaper from an economic, technical, and time standpoint to not do it, or to hide camera tricks and such interactions behind off-screen when passing items.

“But we can be a little more ambitious sometimes, you know what I mean? It’s about how far we can push those boundaries, or how far the characters can go with each other.” It’s time to see how much you can actually interact with, which is probably also why you hugged Aloy so much.

Both Oud and I recall a similar discussion in the gaming community over a year ago. There, a developer surprised many by explaining how difficult it was to do something as simple as making a door that normally opens and closes. Wood said that things like hugs and doors are generally difficult to animate, as well as pausing the game, moving the camera, and other things while the player is performing an activity. He points out that it will be even more difficult in the game space where it is necessary to be able to place. “If you don’t fix it, people won’t believe it and won’t accept it.”

But guerrillas feel that such interactions, especially intimate ones like hugs, are important to the human stories they want to tell, he added. After all, humans do. Some people hug often. It would feel strange that a character in the studio wouldn’t be allowed to do that. I would especially appreciate it if you could help me. But he adds that the success is that the player doesn’t notice them at all.

“Hugging and escaping intimate moments doesn’t tell the story,” says Wood. “So we have to find a way to actually do these things, but still make sure that the feeling and the connection are delivered to the player and the player doesn’t have to think about it. [the players] If you can feel it, we are already happy that we actually achieved our goal. “

Rebekah Valentine is a news reporter for IGN. you can find her on her twitter @duck valentine.