Minecraft in 500 lines of Python

Richard Donkin@rdonkin

cloudfindhq.com

github.com/fogleman/MinecraftEarly version:

http://xkcd.com/353/

Why Python?Easy to write

Great community

Fast enough Can use compilers (Cython etc) or JIT (PyPy)Or use a spare GPU …

Libraries, broad usage

Raspberry Pi to scientific computing to cloud apps

http://xkcd.com/353/

Pyglet3D gaming library - pyglet.org

Simple to learnDoesn’t mandate program structureWraps OpenGLCan use py2exe / py2app

This is a quick Minecraft code walkthrough, not a tutorial

Tutorial based on Asteroids: steveasleep.com

Minecraft Essentials

Objects are blocks, in 3D grid

OperationsMove: W, S, A, D – and Tab to flyMouse to look (or fly)Mouse to add or remove blocks

Textures

OverviewWindow class

Subclass of Pyglet window classUser interaction, movement, rendering

Model classModels the world as blocks in 3D grid

Dictionary world[position]

where position is tuple (x, y, z)Contains texture such as

Window & Startup Code

Model

Look around

X axis is horizontal (look left/right)

Y axis is vertical (look up/down) – max ±90°

Only motion matters, not absolute position

Python tuple assignment

Building stuff

Mouse locking, sight vector

Hit testing, block add/remove

Adding a Block

Remove any existing block at (x, y, z) position from the ‘world dictionary’

Set texture for this block at position

Create or update sector (16x16 2D grid) in which this block resides – enables speedup by only rendering some sectors

Show the block, and check if any neighbours now visible

Highlighting ‘target block’

Hit-test from player position to target block

Draw line around visible edges of block, using Pyglet

1100 commits later…

github.com/boskee/Minecraft

Major fork

8,000 lines

19 contributors

Multi-player

Optionally, compile to C via Cython

Pyglet and More2D game toolkits:

Cocos2D: http://cocos2d.org/ - uses PygletFife: http://www.fifengine.net/ - esp. RTSs and RPGs

Add-on libraries that can work with Pyglet:Rabbyt – sprites: http://arcticpaint.com/projects/rabbyt/ Pymunk – physics: http://pymunk.org

Alternative frameworks:Pygame – larger community, more game-specific, open source book at http://inventwithpython.com/

Summary

Concise, elegant code

Choose the right framework

Small games to get started

Write your own!Try pyweek.org challenges

Thank YouRichard Donkin

@rdonkin cloudfindhq.com

Sect0rization

Technique used to speed up rendering of world – only render nearby sectors

Sector = 16x16 2D region of world In Model, dictionary sectors[sector] maps from sector to list of positions in that sectorTrack player position in sectorIf player moves between sectors, determine which adjacent sectors to show – see change_sectors()