How games like Apex Legends break gravity for fun

“Find the fun.” The common refrain of game development can be expressed in creating a new game mechanic, refining or combining existing mechanics, or making something simple—like jumping, flying, and fighting—great. Even falling.

In games like Fourteen days, Apex LegendsAnd The Legend of Zelda: Tears of the KingdomFalling from the open sky to the hard ground is an experience. Simulated gravity pulls players down, and the game mechanics let them float, spin, and swing as they fall. Simulated air friction can slow their fall, while visual effects like motion lines and field of view tricks help convey a sense of speed. Bouncing back into the sky quickly, whether through bounce pads or simply the power of a character’s two legs, is defined by another force that also has to be fun.

Gravity is part of the physics engine of every video game, says Chris Winder, lead gameplay engineer at Apex Legends Developer Respawn Entertainment. “Gravity in apex is about twice the force of Earth’s normal gravity,” Winder told Polygon in an email. “This, combined with similarly increased jump speeds, is a trick games use to make the game seem faster while still feeling within the bounds of realism.”

Physics simulation is generally considered a feature of simulation games such as the Gran Turismo series or Kerbal Space Programbut Winder points out that “it is present to some degree in almost every game we play, from Super Mario Bros. To Rocket League To Apex Legends.”

Video games can not only manipulate gravity to satisfy their needs, they can also simply ignore it if they want to – anything to feel good, said Jeremy Russo, game director at Velan Studios. His studio’s sports title Knockout City uses a gravity effect inspired by fighting games to enhance the gameplay. (Interestingly, Knockout CityThe gravitational constant follows a different approach than apex; it is about half of the gravity of the Earth.)

“We do this both for gameplay reasons and to improve the feel of the game by temporarily overriding normal gravity and character speed for certain abilities,” Russo explained. Knockout Citythe developer lets your character hover briefly while throwing the ball mid-jump. “The reason for this is that the throwing animation takes a few frames before the ball is released, so if we kept pushing the player’s full speed up or down, the ball would often get thrown into the geometry. It also just felt wrong, so we took a cue from some brawler and fighting games where players briefly hover in the air when performing a melee attack.”

Russo says, “To get it right, we reset the player’s speed when they went down, or set a new, slower speed when they went up, because even hovering at a certain height for multiple frames felt wrong.” His team applied the same method, with varying degrees of customization, to many skills like catching, sprinting and bunching.

“Gravity is a force that pulls things ‘down’ in every single frame of the game,” said Chris Mercado, technical designer at Velan. “The fun is deciding where ‘down’ is!” [We] can play around with size and direction as much as we want. Some games work with a constant universal down (Super Mario 64), others have a custom spherical gravity (Super Mario Bros.); ultimately, gravity works the way the developers need it to in order to make the game they want to make.”

These forces go beyond the expected ups and downs of jumping and falling, Winder said. Apex LegendsPlayers can use jump pads and gravity lifts to push themselves up (and then fall). The same physics-based approach also applies to things like grappling hooks.

“There’s a lot to do to make these elements move players, to make them feel fun and useful,” Winder said. “That might mean accurately simulating the real-world physics of a player being catapulted through the air or pulled by a grappling rope, while also allowing some less realistic inputs into that simulation to give players the control they expect.”

apexThe Legend Pathfinder has a grappling hook that pulls the player toward a grappling point, “but if you look to the side in a certain direction, a small force is applied so players can ‘roll’ the grappling hook in,” Winder explained.

Respawn is similarly spoofing another legend’s ability. “Horizon’s gravity lift applies an upward force to players, but also allows directional inputs to move in and out of the lift,” Winder said. “There’s also a hidden force that sometimes causes people to stay in the lift so they don’t accidentally fall out.”

This type of air control is familiar to players of many games. In the games Super Mario Bros. and Sonic the Hedgehog, you can apply a force to a jumping character to better control their jumps.

“As a developer, I find some things incredibly interesting that are invisible to most players that make platforming significantly more usable,” said Velan’s Jeremy Russo. “The most obvious is air control… in real life, you can’t change your lateral direction mid-air after a jump, but most games give you some degree of control.” Developers use similar tricks for jumps, Russo said, letting players jump a few frames after running off a ledge.

“The control the player has while in mid-jump is one of the most fun aspects to play around with,” said Doug Applewhite, a programmer and designer. “It’s surprisingly difficult to feel good and ‘right’ in this situation, and you have a lot of options to play with.”

“I think it’s important to recognize that jumping is often a player’s first connection with the physics of a game world,” said Hunter Bridges, game director at Penny’s big breakout Developer Evening Star. “The jump intuitively tells the player a lot about how the game works, often within the first few seconds of play.”

Explaining his studio’s approach to jumping in its 3D platform game, Bridges said that Evening Star wanted to ensure that the title character’s “jump occurs without any startup lag.”

“Penny leaves the ground in the first frame that the jump input is detected,” he said. “In some other games, it might be desirable to have a few frames of startup delay to illustrate the anticipation or otherwise better adjust the jump animation.”

Bridges, who also worked on 2D platform games Sonic Maniasaid that crafts jump in Penny’s big breakoutThe 3D space presents a completely different challenge than the classic, sideways platform game “Sonic the Hedgehog”.

“With 3D games, you always have to contend with the fact that the 3D scene is projected onto a 2D screen,” Bridges said. When a game’s 3D camera tilts or rotates, “it becomes difficult to perceive the distance along the camera’s direction due to foreshortening.” 2D platformers don’t have to worry about that.

Developers get around this foreshortening problem, Bridges explained, by making enemies bigger, making players’ jumps higher and making near-misses in 3D games more forgiving by manipulating collision detection and giving players recovery abilities. (“That’s the origin of Penny’s Ledge Pull move,” Bridges said.)

One of the most fascinating implementations of physics related to jumping and gravity is the space exploration game from Mobius Digital Outer Wilderness handles the simple act of jumping, taking into account not only the player’s movement, but also the physics of a small solar system.

“In video games [have] to keep the camera near the center of the world coordinate space, or […] everything starts to shake somehow,” explained Outer Wilderness Co-creator Alex Beachum in a 2020 documentary about the creation of the game. “So we have to keep the player close to the mathematical origin of the world. […] But because [in] We have everything moving relative to each other. What I ended up doing was this: every time we apply a force to the player, we simply apply an opposite force to every physical object in the world that is being simulated.

“So if you jump in Outer Wildernesstechnically every planet jumps out from under you and you more or less don’t move. It works,” Beachum said, “and we haven’t changed it.”

Beachum’s solution to solving a complicated mathematical problem by simulating jumping in Outer Wilderness was created out of necessity, but also serves a higher purpose: to have fun.

“[A] “The player’s intuition about how gravity should work is generally more important than reality,” Mercado said. “That’s why most space combat games have air friction and terminal velocities! Ultimately, we’re creating fun interactive media, so our physics should enable that fun.”