Physics Engines in Gaming: How They Bring Virtual Worlds to Life

In the world of video games, the experience of immersion and realism often hinges on how well the game world behaves according to the laws of physics.

From the arc of a thrown object to the precise simulation of gravity, friction, and collisions, physics engines are the unsung heroes that make virtual worlds feel lifelike.

These computational systems are responsible for ensuring that objects within a game interact with one another and their environment in ways that are believable and consistent with the real world—or, in some cases, delightfully not.

This article dives into the role of physics engines in modern gaming, exploring how they work, how they shape gameplay experiences, and how developers push the boundaries of physics simulation to create immersive, dynamic, and reactive worlds.

What is a Physics Engine?

A physics engine is a software framework designed to simulate physical laws in a video game environment.

It allows developers to simulate interactions like collisions, gravity, momentum, friction, and fluid dynamics without manually programming each individual object’s behaviour.

Instead, the engine uses algorithms to calculate and apply forces based on the game's physics model, making it possible for virtual objects to interact in ways that mimic real-world physics—or intentionally break those rules for fun and creativity.

Physics engines can be divided into two broad categories:

2DPhysics Engines:

Typically used in side-scrolling games or simple platformers, these engines simulate basic interactions in a two-dimensional space.

3DPhysics Engines:

These engines are more complex and are used in open-world, first-person shooters, and other 3D environments to simulate the full spectrum of physics interactions.

Popular physics engines in gaming include Havok, PhysX (by NVIDIA), Bullet, Unreal Engine’s Chaos Physics, and Unity’s built-in physics engine.

How Do Physics Engines Work?

At their core, physics engines rely on mathematical equations to model the physical world.

These equations govern the forces that act on objects, their movement, and how they interact with each other.

Some of the key principles and calculations involved in physics engines include:

Newtonian Physics (Classical Mechanics)

Most physics engines use Newtonian mechanics as a foundation, which is based on three key laws:

1. An object in motion will remain in motion unless acted upon by an external force.

   
   

2. Force equals mass times acceleration (F = ma).

   
   

   This equation helps calculate how objects move in response to forces.

   
   

3. For every action, there is an equal and opposite reaction, which is important for simulating interactions like collisions.

These laws govern how objects move and collide within the game.

When you throw a grenade, for example, the physics engine will calculate the projectile's velocity, the force of gravity acting on it, and how it will arc through the air before hitting the ground and exploding.

Collisions and Rigid Body Dynamics

One of the most important roles of a physics engine is simulating rigid body dynamics, which determines how solid objects react when they collide.

This includes calculating things like:

Impact:

When two objects collide, the engine calculates their velocity, angle of impact, and the material properties of each object (e.g., hardness, elasticity) to determine how they will respond.

A bouncy ball will rebound differently from a metal object.

Friction and Sliding:

When an object moves across a surface, friction influences its motion, slowing it down.

The engine calculates the frictional force, which is determined by the surface properties and the object’s velocity.

Momentum:

When objects collide, momentum is transferred from one object to another based on their mass and velocity.

In games, this is key for simulating realistic car crashes, explosions, or even a simple rock falling down a hill.

Soft Body Dynamics

While rigid body dynamics involves hard, non-deformable objects, soft body dynamics simulates materials that can deform or change shape, such as rubber, cloth, and liquids.

These simulations require complex algorithms that model the way materials stretch, bend, or flow in response to forces.

Cloth Simulation:

In games like The Witcher 3 or Red Dead Redemption 2, you can see characters’ clothing and flags realistically respond to wind, motion, and physics.

This is accomplished through soft body simulations, where the clothing’s individual fibres and vertices are simulated.

Liquid and Gas Simulation:

Games like Subnautica use fluid dynamics to simulate water and gases, with objects floating, sinking, or moving based on the density of the fluid and its buoyancy properties.

Gravity and Forces

Gravity is a fundamental force in most games, affecting how objects fall, bounce, and stay grounded.

In a game like Minecraft, gravity pulls blocks down when they are unsupported.

In more realistic games like Kerbal Space Program, gravity governs the orbits of planets and the trajectory of rockets.

Physics engines use Newton’s law of gravitation to calculate the force exerted by planets or other celestial bodies, affecting how objects move within the game world.

For example, when you jump in Grand Theft Auto V, the physics engine calculates your jump based on gravity, your velocity, and air resistance.

How Physics Engines Enhance Gameplay

Realism and Immersion

Physics engines contribute heavily to immersion by making the virtual world behave in a way that matches our expectations of how the real world works.

For example, in a game like The Last of Us Part II, realistic physics ensures that objects and characters interact naturally with their environment.

When you throw a bottle, it flies in an arc, bounces off surfaces, and falls to the ground in a way that feels intuitive.

Environmental Interactions:

Physics engines also allow objects to react dynamically to changes in the environment.

In Half-Life 2, for instance, players can use the physics-based gravity gun to pick up, throw, and manipulate objects, solving puzzles and creating new interactions in the game world.

Destruction:

Games like Battlefield V and Red Faction: Guerrilla use physics engines to simulate real-time destruction of buildings and environments.

Explosions tear through walls, buildings collapse, and structures deform based on the physical properties of the materials involved.

Dynamic Interactions

One of the exciting possibilities that physics engines bring to games is dynamic interaction.

This is when objects in the world interact with each other in real time, often creating unexpected or emergent behaviour.

For example, in Grand Theft Auto V, you can shoot tires to make cars crash, or in Portal 2, you use momentum and gravity to solve puzzles.

Emergent Gameplay:

Because physics simulations are based on algorithms and not scripted events, they can lead to emergent gameplay where the player can create solutions or chaos that wasn’t explicitly designed by the developers.

The interaction between physics, objects, and the player can result in an almost infinite variety of outcomes.

Player Control and Puzzle Solving

Physics engines are also essential in games that involve puzzle-solving mechanics based on real-world physics.

In The Talos Principle or Portal, the player must use the laws of physics—like gravity, momentum, and energy transfer—to solve complex puzzles.

Realistic Simulations:

In Kerbal Space Program, players need to understand and apply principles of orbital mechanics to launch rockets, explore other planets, and survive in space.

The game’s highly realistic physics engine makes it a fun and challenging way to learn real-world physics concepts.

Customization and Creativity

Games that allow for user-generated content or open-world creativity benefit greatly from the use of physics engines.

In Garry’s Mod or Minecraft, players can manipulate objects, create machines, or engage in physics-driven experiments using the game’s physics engine.

Whether it's stacking blocks to build a house or creating elaborate Rube Goldberg machines, physics engines make this creativity possible and fun.

Sandbox Games:

In sandbox games like Besiege or Human: Fall Flat, the entire gameplay revolves around using the physics engine to solve puzzles or create chaos.

These games let players use objects, materials, and forces in the game world to interact in creative ways, often resulting in unexpected, humorous, or chaotic outcomes.

The Backbone of Virtual Worlds

Physics engines have come a long way since the early days of gaming, transforming from simple simulations of gravity and movement into complex systems that govern every aspect of virtual worlds.

Whether they're simulating gravity on distant planets, making objects fall and collide, or allowing for realistic vehicle handling, physics engines help make games feel more immersive, interactive, and alive.

As gaming technology continues to evolve, physics engines are likely to become even more sophisticated, offering deeper levels of realism or even more creative, fantastical interpretations of physics.

Whether it’s enhancing the realism of a first-person shooter or providing a playground for player-driven experimentation in sandbox games, physics engines are an essential part of modern game development and play a major role in shaping the experiences of gamers worldwide.