mark nelson [email protected] what are game engines? fall 2013
TRANSCRIPT
What’s a game engine? Try #1
Real-time graphics engine? Maybe w/ physics?
Possible features Realistic water Shadows Reflections Destructible terrain
What’s a game engine? Try #2
Integrated game builder?
Possible features IDE Level editor 3d modeling Asset pipeline Debugging Scripting
Engines are lots of things
Libraries Frameworks Collaboration/integration architectures Generic game shells Tools
No engine
In the olden days, you might code a game by: Writing code that implements the game
Engine as library
It’s sometimes nice to reuse code
Collision detection Physics Sprite blitting AI
Engine as library
Engine as library
Bottom-up game-engine development
Write a game, then another one An engine is whatever you can reuse
Can you package that up into a library (or middleware)?
Engine as library
Engine as way of outsourcing complex but modular stuff
What do you need that is hard to implement, but could be plugged in if you had it?
AI, fancy graphics, advanced simulations, advanced physics
Engine as framework
Libraries let us reuse stuff we call out to
Can we reuse some of the structure, too? Check input Update positions Calculate dynamics Redraw screen Manage memory Sync network state
Engine as library v. framework
Defining feature of frameworks is inversion of control And, they’re opinionated about it
Your game Your game
LibraryLibrary
Framework Framework
Your gameYour game
Engine as framework
Defines classes of stuff, and you plug in the specifics
Sprites, objects, levels, events, behaviors
Customize by extending or overriding classes
Instead of bottom-up abstraction, pattern-matching abstraction
In-class exercise
You are a 1-person programming team wanting to make a small-budget game. Do you code from scratch? Use an existing engine? If it depends, what does it depend on?
You are a 50-person team with a large budget. What about now?
[take 5 minutes to discuss]
Engine as collaboration/integration arch.
A lot of people work on a modern game They produce a lot of different stuff
Level designer Dialog-tree writer 3d modeler Graphics programmer AI programmer Network programmer NPC behavior scripter
Engine as collaboration/integration arch.
How do we plug all this stuff together?
An engine architecture provides modularity and interfaces
Asset pipelines Required functionality Dependencies Division of responsibilities
Engine as collaboration/integration arch.
One big boundary: code v. non-code
Architecturally: code v. data
Socially: programmers v. non-programmers
(Lots of other boundaries and interfaces.)
Engine as generic game
Codification of genre conventions
”A Zelda-style engine” ”A platformer engine”
Everything but the game
A very opinionated framework
“Final Fantasy engine”
“Quake 3 engine”
Platformer engine
“Civ 5 engine” ?
Spectrum of engine genericity
Many engines are a mix of ’engine’ and ’game’
Cleaner separation in more established genres
Cleaner separation from game content than dynamics
Engine as game-development tool
Unity as a game-development environment Library, framework, editor, tools
Most engines have an associated toolchain Some 3rd party, e.g. Maya Some custom, e.g. level editor
Spectrum of wizardry RPG Builder, Game Maker Unity UDK
Exercise for next week
Choose an existing game and think about what engine features would make it easy to program similar games An existing engine? Something new? Was the game already built on an engine (if known)? How generalizable is the game?
(I’ll ask in class next week, but you won’t be graded or need to hand the exercise in.)