Introduction to Game Engines

Game Frameworks

Lecture 01: Introduction to Game Engines

Edirlei Soares de Lima

<edirlei.lima@universidadeeuropeia.pt>

What is a Game Framework?

•

A game engine, also known as game

framework, is a software designed for

people to create games.

–

Programming libraries vs complete frameworks

A game engine is extensible and can be

used as the foundation for developing

many different games without major

modification.

Examples:

–

Quake engine (1996), Unreal Engine (1998),

Source Engine (2004), CryENGINE (2004) ,

Microsoft XNA (2006), Unity (2005), Frostbite

Engine (2008), etc...

Examples of Game Engines

•

Unity

– https://unity.com/

Unreal Engine

–

https://www.unrealengine.com/

Examples of Game Engines

•

CryENGINE

– https://www.cryengine.com/

Godot

–

https://godotengine.org/

Examples of Game Engines

•

GameMaker

– https://www.yoyogames.com/g

amemaker

RPG Maker

–

https://www.rpgmakerweb.com

Game Engine Architecture

•

A game engine generally consists of a runtime component and

a tool suite.

Like most software systems, game engines are built in layers.

.

Digital Content Creation Tools

•

A game engine’s input data comes in a wide

variety of forms (3D mesh data, texture

bitmaps, animation data, audio files).

All of this source data must be created and

manipulated by artists.

Game Engine Architecture

•

A game engine’s tool suite may be architected in any number

of ways:

•

Stand-alone pieces of software;

•

Built on top of some of the lower

layers used by the runtime

engine;

•

Built into the game itself.

Low-Level Engine Systems

•

Low-level support systems:

–

Crucial tasks: starting up and shutting down the engine, managing the

engine’s memory usage, handling access to file systems, providing

access to a wide range of asset types, and providing debugging tools.

–

Example: Optimizing Dynamic Memory Allocation

Problem: Memory Fragmentation

Low-Level Engine Systems

•

Low-level support systems:

–

Example: Optimizing Dynamic Memory Allocation

Stack-Based Allocators

Double-Ended Stack Allocators

Low-Level Engine Systems

•

Low-level support systems:

–

Example: Optimizing Dynamic Memory Allocation

Low-Level Engine Systems

•

Low-level support systems:

–

Example: Optimizing Dynamic Memory Allocation

•

When differently sized objects are being allocated and freed in a random order,

neither a stack-based allocator nor a pool-based allocator can be used.

•

Solution: periodically defragmenting the heap

Low-Level Engine Systems

•

Low-level support systems:

–

Example: Game Loop

while (!quit)

{

updateCamera();

updateSceneElements();

renderScene();

swapBuffers();

}

•

A game is composed of many subsystems that require periodic servicing (updates)

while the game is running: device I/O, rendering, animation, collision detection,

rigid body simulation, multiplayer networking, audio, etc.

•

The rate at which these subsystems need to be serviced varies from subsystem to

subsystem.

Low-Level Engine Systems

•

Low-level support systems:

–

Example: Game Loop

• Multiprocessor Game Loops

Rendering Engine

•

One of the basic tasks of a game engine is rendering 2D or 3D

objects:

–

Taking a scene, or model, composed of many geometric objects arranged

in 3D space and producing a 2D image that shows the objects as viewed

from a particular viewpoint.

–

Rendering involves considering how each object contributes to each pixel.

Rendering Engine

•

Rendering Pipeline:

Rendering Engine

•

Example of problem: aliasing

Rendering Engine

•

Optimizations: handling large game worlds

–

Scene graphs: quadtrees, octrees, BSP trees, etc.

Animation Systems

•

The majority of modern games revolve around characters that

need to move in a fluid and organic way.

–

Sprite animation:

–

Skinned animation:

Animation Systems

•

Example of problem: animation blending

Physics Engine

•

Rigid body dynamics and collision detection.

–

Rigid body: infinitely hard and non-deformable solid object.

–

Dynamics: process of determining how rigid bodies move and interact

over time under the influence of forces.

Many game engines make use of a physics middleware:

–

PhysX: https://developer.nvidia.com/physx-sdk

Havok: https://www.havok.com/havok-physics/

ODE: http://www.ode.org/

Box2D: https://box2d.org/

Audio Engine

•

Games immerse the player in a realistic virtual environment

and audio is an important tool to accurately reproduce what

the player would actually hear if he were present in that

environment.

Audio Engine

•

As the rendering process, audio also can have a dedicated

pipeline.

Audio Engine

•

Context-Sensitive Dialog