Game Programming Foundations & Game Engine Architecture

87 Pages·2015·3.53 MB·English

Game Programming Foundations
& Game Engine Architecture
Guillaume Bouyer, Adrien Allard
[e-mail]
www.ensiie.fr/~bouyer/
[e-mail]
Objectives and schedule http://www.ensiie.fr/~bouyer/JIN
Office 111 @ ENSIIE
Understand the theoretical and technical components of game engines
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Be aware of the technical problems and existing solutions that underpin the
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development of a video game (among others to succeed as well as possible in the
project team)
Operate a high-level but relatively closed game engine (Unity). Being able to create
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a project that looks like a game

Monday afternoon: Course Part. 1
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(cid:1) Homework: Install Unity 4 or 5, read Unity course and finish introduction tutorial (from
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ENSIIE-2A IRV)
Tuesday morning : Course Part. 1 + Tutorial Part. 1
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(cid:1) Homework: Continue tutorial
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Thursday: Course Part. 2 + Tutorial Part. 2
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(cid:1) Homework: Finish tutorial
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Friday: Adrien Allard, Amplitude Studios, Talk + Tutorial Part. 3
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(cid:1) Homework: Finish tutorial
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Main Reference
Game Engine Architecture, Jason Gregory
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Published: June 15, 2009 by A K Peters/CRC Press
http://www.gameenginebook.com/

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Outline
Part 1 Part 2

1. Introduction 7. Game World & Game Flow Management
Game, gameplay, game engine & game team 8. Tools for development and debug
Components of a game engine (runtime engine 9. Low and mid-level engine features
architecture)
Configuration
2. Gameplay, game world, game objects
Startup and shutdown
Gameworld
Memory management
Game objects & models
Containers
World editor
Strings
Assets & tools
File system
3. Real-time simulation
Resource manager : off-line & runtime
Game loop
10. Collisions & Rigid body dynamics
Time management
Physics in a game
4. Game objects management
Collision detection
Game Object Architectures and IDs Rigid body dynamics
Real-time object updating
5. Events system
6. Scripts
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1. Introduction
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Video Game?
A Theory of Fun for Game Design, Raph Koster: “An interactive experience that
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provides the player with an increasingly challenging sequence of patterns which he
learns and eventually masters”
Game Engine Architecture, Jason Gregory: "Soft real-time interactive agent-based
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computer simulations"
Simulation
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Approximated and simplified mathematical (numerical) model of the game world
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Game loop: during each iteration, various game systems (artificial intelligence, game logic, physics
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simulations…) calculate or update their state for the next discrete time step
Rendering of the result by displaying graphics, sound, and possibly other outputs
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Soft: missed "deadlines" (rendering, physics, audio…) are not catastrophic
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Real-time: dynamic game world model
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Agents: distinct entities or objects in interaction
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Interactive: must respond to unpredictable human input
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Artistic content designed to entertain players
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Gameplay?
Interactive experience of the player(s)
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"Game Mechanics"
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Rules of interactions between the entities
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Objectives, criteria for success and failure
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Player character’s abilities
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Number and types of non-player entities in the virtual
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world
Overall flow of the gaming experience
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More crucial to define a game more than its
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technology
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Game Engine?
Mid-1990s: some games architected with a separation between
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Core software components (3D graphics rendering system, collision
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detection system, or audio system)
Art assets, game worlds, and rules of play that made the gaming
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experience
Ex: Doom (id Software)
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=> Create new games with new contents & minimal changes
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to reusable core software
=> Mod community
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=> Engine licensing as a viable secondary revenue stream
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Game Engine?
Software that is extensible and can be used as the foundation
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for different games without major modification
Trade-off’s between generality and optimality
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The more general-purpose a game engine or middleware component
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=> the less optimal for running a particular game / particular platform
Assumptions about how the software will be used and/or about the
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target hardware on which it will run
Sets of tools + runtime components
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Data-driven architecture
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Typical Game Team
Engineers (= programmers)
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Runtime programmers: engine and game
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Single engine system: rendering, AI, physics…
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Low level: memory, network…
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Gameplay (3C : Character-Controls-Camera)
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Tools programmers: off-line tools for the team
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=> Lead engineers (+ management), technical directors (high level),…
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chief technical officer (for the entire studio)
Artists Produce visual and audio content
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Concept artists, 3D modeler, Animators, Texture & lighting artists,
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Actors (mocap, voice), Sound designers & composers…
=> Lead artists, art directors
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Typical Game Team
Game designers Design the gameplay
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Macro level
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Story arc, overall sequence of levels, high-level objectives of the player
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Individual levels or geographical areas within the game world
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Static background geometry, enemies spawning, items placement, puzzle elements…
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Technical level
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Close with gameplay engineers and/or writing code (high-level scripting language)
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=> Game director
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Producers
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Manage the schedule, the human resources, link between the dev. and the
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business units…
Publishers
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Marketing, manufacture and distribution (usually not handled by the studio)
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Data-Driven Game Engine
Game team must efficiently produce very large
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amounts of contents
Data-driven engine permits designers and artists to
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Create content
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Control, in whole or in part, the behavior of the game
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Directly by data rather than exclusively by engineering
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programming
Benefits and risks
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Improved iteration times
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Heavy cost to develop appropriate runtime code and
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robust and usable tools
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Engine Differences Across Genres
Particular technological requirements for each genre => Game engines have traditionally differed from
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genre to genre
First-Person Shooters (FPS)
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efficient rendering of large 3D virtual worlds (optimized for a particular type of environment)
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responsive camera control/aiming mechanic
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forgiving player character motion and collision model (“floaty”)
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high-fidelity animations of the player’s virtual arms and weapons
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wide range of hand-held weaponry and pickable items
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high-fidelity animations and AI for the non-player characters (enemies and allies)
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small-scale online multiplayer capabilities (ex. 64), “death match” gameplay mode…
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Platformers and other Third-Person games
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~FPS
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emphasis is placed on the main character’s abilities and locomotion modes
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high-fidelity full-body character animations for the player’s avatar
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interesting locomotion modes: moving platforms, ladders, ropes…
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puzzle-like environmental elements
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third-person “follow camera” focused on the player character + complex camera collision system
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Engine Differences Across Genres
Fighting games
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typically 2 players
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rich set of high-fidelity fighting character animations
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high-definition character graphics (realistic skin, sweat effects…)
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physics-based cloth and hair simulations
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accurate hit detection
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user input system capable of detecting complex button and joystick combinations
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relatively static backgrounds (crowds)
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Racing games
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usually focus all graphic detail on the vehicles, track, and immediate surroundings
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various “tricks” to optimize rendering (distant background elements…) and aid AI (path finding for
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non-human-controlled vehicles…)
follow camera (3rd-person) or inside the cockpit (FPS)
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realistic physics (tires, materials…) and audio
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Engine Differences Across Genres
Real-Time Strategy (RTS)
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typically oblique top-down camera, restrictions allow to optimize the rendering
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grid-layout system to aid align units and buildings
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units relatively low-res, to support large numbers on-screen
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height-field terrain
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user interaction: single-click and area-based selection of units, menus or toolbars containing
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commands, equipment, unit types, building types…
Massively Multiplayer Online Games (MMOG)
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powerful battery of servers to maintain the authoritative state of the game world, manage users
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signing in and out of the game, provide inter-user chat or VoIP services…
central server to handle the billing and micro-transactions
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graphics fidelity almost always lower than non-massively multiplayer counterparts, as a result of the
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huge world sizes and extremely large numbers of users supported.
Technological overlap between genres, especially within the context of a single hardware
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platform
More and more powerful hardware => differences between genres are decreasing
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=> increasingly possible to reuse the same engine technology across disparate genres, and
even across disparate hardware platforms 15
Game Engine Examples
Quake Family (Id Software)
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Castle Wolfenstein 3D (92), Doom, Quake I II III, Medal of Honor…
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Unreal Family (Epic Games)
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Unreal (98), Unreal Tournament 2004, Gears of War…
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Source Engine (Valve)
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Half-life 2, Team Fortress, Portal…
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Microsoft’s XNA Game Studio
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Unity 3D
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Proprietary in-House Engines
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Open Source Engines
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Ogre 3D, Panda3D, Yake, Crystal Space, Torque, Irrlicht…
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Runtime Engine Game-Specific Subsystems
Game-Specific Player Game Camera AI
Rendering Mechanics
Architecture
Gameplay Foundations
Front End

Game Game
Events Scripting
Objects Flow
Visual Effects
Skeletal Online
Audio
Scene-graph / Culling Animation Multiplayer
Optimizations
Human
Profiling & Collision &
Low-Level Renderer Interface
Debugging Physics
Devices
Resources Resources / Assets Manager
/ Assets
Core systems
Platform Independence Layer
3rd Party SDKs
OS
Drivers
Hardware
Runtime Engine Architecture
Target hardware
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Drivers
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Low-level software components provided by the OS or hardware vendor
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Manage hardware resources and shield the operating system and upper engine layers
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from the details of communicating with all the variants of hardware devices available
Operating System (OS)
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PC
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OS runs all the time
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Orchestrates the execution of multiple programs, including the game
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Pre-emptive multitasking: time-sliced approach to sharing the hardware
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Console
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Previously a thin library layer compiled into the game executable: game "owns" the machine
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Now can interrupt the execution of the game, or take over certain system resources, in order to
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display online messages, or to allow the player to pause the game and bring up the dashboard
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Runtime Engine Architecture
Third-Party SDKs and Middleware
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Data Structures and Algorithms
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STL, STLport, Boost…
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Memory allocation performance vs. convenience?
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Graphics
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OpenGL, DirectX, libgcm (PS3), Edge (Naughty Dog)…
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Collision and Physics
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Havok, PhysX, ODE, I-Collide, V-Collide, RAPID…
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Character Animation
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Granny, Havok Animation, Edge…
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Artificial Intelligence
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Kynapse…
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Biomechanical Character Models
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Endorphin and Euphoria
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Platform Independence Layer
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Wrap or replace the most commonly used standard C library functions, OS calls, and other foundational APIs
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Shields the rest of the engine from the majority of knowledge of the underlying platform
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Runtime Engine Architecture
Core Systems: useful software utilities
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Assertions, unit testing…
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Memory allocation
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Math library, random number generator
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Custom data structures and algorithms
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Resource Manager
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Interfaces for accessing game assets and other engine input data (3D model, texture, material, font,
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skeleton, collision, map…)
Unified or suite of tools
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Profiling and Debugging Tools
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Profile performance and analyze memory in order to optimize
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In-game debugging facilities
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Record and play-back gameplay
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Config, stats…
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Commercial or custom
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