Minecraft in 500 lines of Python

Richard Donkin@rdonkin

cloudfindhq.com

http://xkcd.com/353/

Why Python?

Easy to write

Great community

Fast enough Compilers (Cython)JIT (PyPy)

3D and Game Libraries

http://xkcd.com/353/

Demo

github.com/fogleman/Minecraft - Michael Fogleman

Early version:

Minecraft Essentials

Objects are blocks, in 3D grid

OperationsMove: W, S, A, DLook around: move mouseAdd or remove blocks: click mouse

Textures

How Pyglet Helps3D gaming library - pyglet.org

Simple wrapper for OpenGLPure PythonLibrary not a framework

This is a quick Minecraft code walkthrough, not a Pyglet tutorial

Tutorial based on Asteroids: steveasleep.com

Overview of Structure

Window classSubclass of Pyglet window classUser interaction, movement, rendering

Model classModels the world as blocks in 3D grid

“The Whole World is an (x, y, z) Dictionary”Dictionary world[position]

Where position is tuple (x, y, z)Each entry contains texture such as

Window & Startup Code

Building stuff

Mouse locking, sight vector, hit testing

Remove Block – STONE is special

Look around

Motion matters (dx, dy), not absolute position

Get ‘look vector’ rotation (as x, y degrees) & add proportion of motion

Mouse left/right is x (look left/right)

And forward/back is y (look up/down) – max ±90°

Highlighting ‘target block’

Hit-test from player position to target block

Draw line around visible edges of block, using Pyglet

Model

Adding a Block

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

Set texture for this block at position

Update sectors (16x16 2D grid) to record this block

Enables speedup by only rendering some sectors

Show the block, and check if any neighbours now visible

1100 commits later…

github.com/boskee/Minecraft

Major fork

8,000 lines

19 contributors

Multi-player

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/

Wrap Up

Concise, elegant code

You can do a lot in 500 lines!

Thank YouDownload slides:

https://www.slideshare.net/rdonkin/minecraft-in-500-lines-with-pyglet-pycon-

uk

Richard 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()