The Last of Us Part 2 is a massive game obsessed with tiny details, and nowhere is this more apparent than when we take a look at how the game handles ropes and cables.
Midway through the first in-game day, The Last of Us Part 2 tasks players with opening the gates to Seattle’s quarantine zone, which means hooking up a generator to the right control panel. Most people will take the supplied lengthy cable and plug it in to the appropriate box, but if you stop around and mess with it, you’ll discover that the game grants you a surprising amount of freedom with how you use the cable. This might explain why footage of this early scene, which is otherwise completely unremarkable, went viral on Twitter over the weekend.
A Japanese developer shared a short clip showing off many of the cable’s intricate behaviors, including realistic bunching, looping, and swaying, but perhaps most notably, the way it actually takes its surroundings into account. As Ellie throws it around, the cable will get stuck on parts of the environment — unless she moves or handles it in a different way.
Many game developers remarked on the mechanic on Twitter, including one Xavier Coelho-Kostolny, who you might remember as the person who once sculpted Spider-Man’s nipples. “I guarantee this caused about 15 different people to cry during production,” the 3D character artist joked. The tweet by response Coelho-Kostolny also went viral as folks marveled at the details.
“The fact that it’s all completely interactive is absolutely bananas,” one animator said in the thread.
So, what makes this cable, and the game’s general usage of rope, so remarkable in the first place? In an email to Polygon, Coelho-Kostolny explained that recreating certain types of physics and physical interactions in video games is surprisingly difficult, at least for this type of flexible material. While there are widely used solutions for the physics and behaviors of stiff objects, it’s another story for things like the cable in the video above.
“Unlike a box or barrel, a piece of cloth, rope, or other flexible material needs to constantly be able to change how and where it collides with other objects … and itself,” Coelho-Kostolny said.
Coelho-Kostolny explained that, most of the time, developers settle for creating something like “a string of invisible bones that acts like a chain and pulls sections of the cloth model around.” Anything more complex than that may not be worth the time or effort.
Not so in The Last of Us Part 2, he noted. Naughty Dog’s bleak adventure game uses what is called an automated solution that makes it possible for rope and cable to interact with its environment in all sorts of complicated ways.
“Most simulations of cables or ropes in games aren’t much more complex nowadays than they were 16 years ago in Half-Life 2,” he said. “In that case, cables were just a line stretched between two points, and the middle could move and wave around a bit. What the rope in the Last of Us 2 shows is a series of complex behaviors, like wrapping around objects with complex collision, as well as maintaining the correct length and applying opposing force to the main character.”
The amount of effort and coordination something this small would require across different teams at Naughty Dog is noteworthy, Coelho-Kostolny mused.
“The people who coded and implemented the rope feature would need deep knowledge of the game’s physics systems as well as the systems involved in applying that to art assets,” he said. “The QA team would have to be dedicated to identifying extremely specific edge cases where this rope simulation breaks, and be in constant communication with the programming team. Additionally, there would have to be art and animations created specifically for this rope and Ellie to show and how she interacts with it.”
On Twitter, Naughty Dog technical animator Maksym Zhuravlov — who helped determine how characters would handle rope — was happy that folks noticed this “subtle” detail, which he says took an “insane” amount of code support. He also clarified that the whole thing was a team effort, as the physics were programmed by Jaroslav Sinecky, and further finessed by Sandeep Shekar. And then, of course, the quality assurance team made sure everything worked properly. Even something tiny like this takes a small village, if not crunch.
Yeiii. People finally noticed my subtle rope-carry things ^^. (Don’t try it at home, amount of code support it needs is insane) https://t.co/6yuC2TxrWY
— Maksym Zhuravlov (@MaksZhuravlov) June 20, 2020
Zhuravlov also revealed that, all things told, getting this into the game took about three months of work. Nobody cried, but there was a lot of swearing. It may have taken a lot of time and effort, but Naughty Dog devs seem relieved that folks playing their game took notice of it in the first place.
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