Game engines can seem intimidating for aspiring game developers. But making your own simple game engine can be a fun learning experience and empower you to create the games you want. In this comprehensive guide, you'll learn the key aspects on How to make a game engine from scratch.
While commercial engines like Unity and Unreal Engine provide awesome tools for game development, making your own engine allows for limitless customization and control. With your own engine, you can tailor every aspect to fit your game's unique needs. Building an engine also helps you deeply understand how game engines work under the hood. This knowledge will make you a better game programmer down the road.
Some other benefits of making your own game engine include:
So if you want full creative freedom and a great programming challenge, building an engine from scratch may be for you. Just be ready to invest significant development time.
To build a game engine, you'll need:
Many engine components can be built separately as libraries, like renderers, resource managers, etc. This modular approach lets you swap out parts of the engine as needed.
Now let's break down the major components that go into a game engine:
The rendering engine is responsible for drawing and displaying graphics each frame. It communicates with the GPU (graphics processing unit) to turn 3D models and environments into 2D images on the screen.
The key tasks of a rendering engine include:
For beginners, start by rendering simple 2D sprites, shapes and images. This will teach fundamentals like submitting geometry to the GPU, configuring shaders, managing render state and displaying outputs.
Slowly add support for features like animated 3D models, environment maps, normal/bump mapping, shadow mapping, and different lighting techniques. Aim to have sufficient rendering capabilities for simple 3D scenes before expanding the engine's feature set.
Some key graphics APIs to use for rendering include OpenGL, Direct3D, Vulkan, and Metal.
The windowing system creates and manages application windows to display graphics on screen. The input system detects and responds to user input from devices like keyboard, mouse and gamepad.
Windowing
The windowing system handles tasks like:
Popular cross-platform windowing libraries:
| Library | Description |
|---|---|
| SDL | Simple windowing capabilities with OpenGL support |
| GLFW | Focused on OpenGL context creation |
| SFML | Simple windowing as part of broader framework |
Input
The input system detects and processes different input events:
Input APIs like SDL, GLFW and SFML provide cross-platform input event handling.
Prioritizing keyboard/mouse input early on is recommended, along with basic gamepad support. Multi-touch can be added later as needed.
The resource management system loads game assets like textures, 3D models, audio clips, and other data for use during gameplay. Resources are identified by unique string IDs rather than directly using file paths.
Key Responsibilities
Typical Game Resources
| Resource Type | File Formats |
|---|---|
| Textures | PNG, JPG, TGA, DDS |
| 3D Models | FBX, OBJ, DAE, GLTF |
| Audio | WAV, MP3, OGG |
| Shaders | GLSL, Cg, HLSL |
| Game Data | JSON, XML, custom formats |
Resource Manager Design
The resource manager can be designed as a centralized singleton system that handles asynchronous loading requests from other engine systems and game code.
thread can be dedicated to streaming resources from disk or networked sources to minimize load hitches.
A cache stores loaded resources for fast access based on string IDs. The manager unloads resources based on configurable caching policies, like a Least Recently Used (LRU) scheme.
The game loop is the central engine component that drives all gameplay and rendering. It runs continuously to process input, update game logic, render scenes, and handle events.
Typical Game Loop Steps
On each loop iteration, the game loop performs this sequence of operations:
This loop runs at the target frame rate, often 60 times per second, to provide smooth real-time interaction.
Variable Timestep
Rather than fixed timesteps, it's better to support variable delta times based on actual frame duration:
This ensures consistent gameplay independently of frame rate.
Game Loop Architecture
The game loop can be implemented as its own class or module. It encapsulates the core real-time gameplay architecture.
Other engine systems hook into the game loop by registering update functions to be called each frame. The loop itself is platform-agnostic.
Scenes represent levels or areas in the game world. They contain game objects like characters, items, terrain, etc. The scene system organizes game objects for efficient rendering and simulation.
Scene Graph
A scene is structured as a graph or tree of game object nodes:
This allows complex object hierarchies to be built and manipulated efficiently.
Typical Scene Nodes
| Node Type | Description |
|---|---|
| StaticMesh | A complex mesh object that does not move |
| SkeletalMesh | An animated character model |
| Camera | A viewpoint from which the scene is rendered |
| Light | A light source like a point or directional light |
| ParticleSystem | A simulated particle effect like smoke |
Game Object Implementation
Game objects encapsulate data like meshes, materials, physics bodies, and behaviors. They expose functionality through interfaces like:
This separates object capabilities from their specific implementations.
Scenes and game objects are core engine components that enable efficient scene management and rendering.
The physics engine simulates Newtonian physics for realistic object interactions including collisions, dynamics and constraints. This brings the game world to life.
Key Physics Areas
Rigid Body Physics
The physics engine treats objects like rigid bodies that respond to forces and torque over time:
Integrating these values simulates realistic movement and collisions.
Popular Physics Engines
| Engine | Description |
|---|---|
| Box2D | 2D physics for games |
| Bullet | Real-time 3D physics |
| PhysX | Robust 3D physics from Nvidia |
| Havok | Cross-platform physics SDK |
Box2D is a great choice for 2D games. Integrating a dedicated physics engine offloads thousands of lines of complex code.
Optimization
Complex physics are expensive to simulate. Techniques like spatial partitioning, sleeping inactive objects, and avoiding unnecessary work are key for optimal performance.
Physics brings key aspects of real-world physical behavior to games, like collisions, gravity, mass, friction, springs, joints and fluid dynamics. This vastly expands the potential for interesting mechanics and gameplay.
Spatial partitioning refers to dividing game world space into regions and layers to organize objects for efficient operations like culling and queries.
Types of Spatial Partitions
| Type | Description |
|---|---|
| Grids | Divide world into grid cells like cubes |
| BSP Trees | Binary space partitioning tree |
| Octrees | Recursively subdivide space into octants |
| Quadtrees | Recursively subdivide space into quadrants (2D) |
Benefits
Grid Implementation
A simple grid divides world space into equal cube cells like 10 x 10 x 10. Game objects are grouped into whatever cell their position falls inside.
Cells outside camera view can be quickly skipped. Neighboring cells are checked for proximity queries.
BSP Trees
Binary space partitioning recursively subdivides space with splitting planes. This builds a tree structure useful for segmentation, culling and queries.
BSP trees have fast query times but rebuilding the tree with dynamic data is expensive.
Octrees
Octrees recursively subdivide cubes into eight octants until a size threshold is met. Octrees are common in 3D games for view frustum culling and proximity queries.
Spatial partitioning tailors data access patterns around 3D spatial locality. This brings huge performance gains.
The animation system brings game models to life by controlling their motions, blending animations, and allowing for dynamic effects during gameplay.
Animation Types
| Type | Description |
|---|---|
| Skeletal | Bones and skins attached to models |
| Vertex | Animating individual mesh vertices |
| Morph Target | Blending between predefined vertex positions |
Skeletal Animation
Most common. Skinned model has internal bone skeleton animated by changing bone orientations over time. Smooth transitions between animations are achieved by blending.
Controls
Animations can be triggered based on game logic and input:
State Machines
Manage blending between animation states like idle, walking, attacking. Popular for controlling character movement.
Animation Data
Stored in formats like FBX, COLLADA, glTF. Provides bone hierarchies, pivot points, and keyframe position/rotation data.
Animation systems bring characters and models to life with natural, dynamic motion. This immensely expands the expressive potential of games.
The audio system plays sound effects and background music to heighten immersion during gameplay.
Key Features
Audio APIs
| API | Description |
|---|---|
| OpenAL | Cross-platform 3D audio |
| FMOD | Robust audio engine and authoring tool |
| XAudio2 | Low-level audio on Windows |
Sound Resource Formats
Implementation
The audio system interfaces with a backend API to handle playback. Sounds are triggered from game code and can be positioned in 3D space. Background music loops seamlessly.
Optimizations like object pooling minimize latency. Streaming large audio files avoids hogging memory.
Immersive audio expands the sensory experience dramatically. Engine audio brings environments and gameplay to life.
Scripting provides a framework for implementing game mechanics, behaviors and logic without hard-coding everything into the engine.
Benefits of Scripting
Lua
A popular embedded scripting language. Easy to interface with C/C++.
Typical Gameplay Scripts
| Script | Description |
|---|---|
| CharacterController | Handles player movement and actions |
| AIController | Manages AI behavior and decision making |
| DialogManager | Controls dialog sequences and branching |
| QuestManager | Manages quest objectives and states |
| UIManager | Updates UI elements and handles events |
Implementation
The scripting system allows code scripts to be attached to game objects. Scripts expose functions the engine can call like Start(), Update(), OnCollision(), etc.
Script state is maintained securely between engine updates. Some overhead occurs when crossing the native/scripting language barrier.
Combined with other engines systems, scripting provides the framework for implementing all gameplay elements like game modes, rules, sequences, UI, and more that make your game unique.
Building a full-featured game engine is a massive undertaking. Scope creep can quickly sabotage your progress. That's why it's smart to start small and simple.
Aim to make a basic 2D engine first. Get a window opening, sprites rendering, and basic input working. Expand the engine piece by piece after that, like adding a physics engine or 3D renderer.
Some helpful starting points:
Choosing a clear subset of features to tackle first will get your engine off the ground smoothly. Resist adding everything at once. Focus on core functionality before polish.
Don't reinvent the wheel unnecessarily. Many excellent open source libraries exist for common tasks like audio, input, image loading, networking, GUI, etc. Integrate established libraries into your engine to avoid writing boilerplate code.
Some popular C++ libraries used by game engines include:
Do some research to find libraries that suit your engine requirements. They will provide helpful building blocks.
Performance is critical for good gameplay. A sluggish framerate ruins immersion. Here are some tips for optimizing engine speed:
The key is only doing work that contributes directly to better visuals or gameplay. Constantly measure frame times and aim for 60+ FPS.
To recap, here are some key takeaways:
While creating a game engine from scratch is challenging, doing so can teach you an immense amount about real-time graphics, physics, gameplay programming, and more. Apply an iterative approach to build your skills progressively. Before long, you'll have your own custom engine powering the games you've always wanted to create!
Building your own game engine from the ground up is a challenging but rewarding endeavor.
While existing engines like Unity provide plenty of power out of the box, creating your own engine enables complete customization and control for your specific game. Start with a minimal prototype, leverage helpful libraries, focus on core functionality first, and expand the engine incrementally.
Optimization and rapid iteration are key. With perseverance and incremental progress, you'll gain deep knowledge of real-time graphics, physics, gameplay programming, and more. Before you know it, your custom engine will be powering the games you’ve dreamed of making. The journey to create your own game engine teaches you invaluable skills along the way.
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A: Game engine development refers to the process of creating a software framework that is used to build, develop, and run video games. It involves writing code, designing systems, and implementing various features that are necessary for creating a functioning game.
A: Making your own game engine can be a rewarding experience for several reasons. It allows you to have full control over the development process, customize the engine to fit your specific needs, and gain a deeper understanding of the inner workings of game development.
A: While having programming knowledge certainly helps, you don't need to be an expert to create a game engine. However, a basic understanding of programming concepts, such as variables, loops, and functions, is necessary to start the process.
A: Game engine development involves various aspects, including rendering graphics, handling user input, managing game assets, implementing physics simulations, and creating an efficient game loop. These are some of the key components that need to be considered when building a game engine.
A: Absolutely! Using an existing game engine, such as Unity or Unreal Engine, can save you a lot of time and effort. These game engines come with built-in tools and features that make game development easier for developers of all skill levels.
A: Some popular game engines that you can use for developing your games include Unity, Unreal Engine, Godot, and SDL. Each of these engines has its own set of features and benefits, so it's important to choose one that aligns with your specific needs and goals.
A: The time it takes to create a game engine can vary depending on the complexity of the engine and the skill level of the developer. It can take anywhere from several months to several years to develop a fully functional game engine.
A: Some commonly used programming languages for game engine development include C++, C#, Java, and Python. These languages offer robust capabilities and are widely supported in the game development community.
A: Yes, you can create a game engine specifically tailored for a certain type of game, such as a 2D game. By focusing on the requirements and unique aspects of the game genre, you can develop a game engine that optimizes performance and provides the necessary tools for creating immersive gameplay.
A: Yes, there are resources available that can help you learn how to make a game engine. Online tutorials, books, forums, and online communities dedicated to game development are great options for gaining knowledge and guidance throughout the process.
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