Löve and Luabased on

http://nova-fusion.com/2011/06/14/a-guide-to-getting-started-with-love2d/

Löve

•2D game framework

•simple to use

•free

Game Structure•a folder with main.lua, other files

• to distribute, just create a zip file of the directory contents, and give the zip file a .love extension:

• cd humpy

• zip -r ../humpy.love *

• ... then you can double click the .love file to run it

Löve’s API• the “love” module is a Lua table, containing

• the various other modules (also tables)

• audio,image,graphics,mouse, keyboard,physics,etc.

• many modules contain classes, eg Image

• callbacks are defined in the love module

• let your program handle events, draw, update,etc

• you don’t have to define all of them, just the ones you need (exist default versions of each (most do nothing))

callbacks in love module

•love.load() -- one-time setup

•love.draw() -- to render the frame

•love.update() -- to update simulation

•love.mousepressed(), love.mousereleased()

•love.run() -- main loop

function love.load() player={} player.vx = 10 player.vy = -30 player.x = 320 player.y = 240 image = love.graphics.newImage("masonic-eye.jpg")end

function love.update(dt) player.x = player.x + player.vx * dt player.y = player.y + player.vy * dtend

function love.draw() love.graphics.print( tostring(player.vx), 300,200 ) love.graphics.print( tostring(player.vy), 350,200 ) love.graphics.draw ( image, player.x, player.y)end

function love.mousepressed ( x, y, button ) if button == 'l' then player.x = x player.y = y endend

~tebo/4849/Love/simple

•for drawing lines, shapes, text

•Image and Drawable objects

•reading images and fonts

•managing framebuffer

•special objects like particle systems

love.graphics

screen coordinates

Points

•love.graphics.point ( x, y ) --draws a point

•love.graphics.setPointSize ( size )

•love.graphics.setPointStyle ( style )

function love.load() stars = {} max_stars = 100 for i=1, max_stars do local x = math.random( 5, love.graphics.getWidth()-5) local y = math.random( 5, love.graphics.getHeight()-5) stars[i] = {x, y} end love.graphics.setPointSize ( 3 ) love.graphics.setPointStyle ( "smooth" )endfunction love.draw() for i=1, #stars do -- loop through all of our stars love.graphics.point( stars[i][1], stars[i][2]) -- draw each point endend

~tebo/4849/Love/stars

•love.graphics.line ( x1,y1, x2, y2, ... )

•love.graphics.line (table_of_points)

•love.graphics.setLineWidth ( w )

•love.graphics.setLineStyle ( style )

Lines

~tebo/4849/Code/Love/lines

function love.load() points = { 0, 0 }endfunction love.draw() x, y = love.mouse.getPosition() love.graphics.setColor ( 255, 0, 0 ) love.graphics.line ( 320, 240, x, y ) points[#points + 1] = x points[#points + 1] = y love.graphics.setColor ( 0, 255, 0 ) love.graphics.line ( points )end

Drawables

• drawable = love.graphics.newImage ( “filename” )

• drawable = love.graphics.newParticleSystem ()

• love.graphics.draw( drawable, x, y, r, sx, sy, ox, oy )

~tebo/4849/Code/Love/flyeye

function love.load() skyeye = love.graphics.newImage("masonic-eye.jpg") width = skyeye:getWidth() height = skyeye:getHeight() angle = 0 rotvel = 10end

function love.update(dt) angle = angle + rotvel * dtend

function love.draw() love.graphics.draw( skyeye, 100, 100, math.rad(angle), 1, 1, width / 2, height / 2)end

love.audio

•‘Source’ object -- can be played

•use OpenAL (directional sources, listener)

•(not working on mac???)

•sounds are “static” (in RAM) or “stream”

noisyfunction love.load() love.graphics.setBackgroundColor ( 255,255,255 ) music = love.audio.newSource("overbeated.ogg") -- if "static" is omitted, LÖVE will stream the file from disk, good for longer music tracks music:play() listener={} listener.listenerImage = love.graphics.newImage ( "listener.png" ) listener.w = listener.listenerImage:getWidth() listener.h = listener.listenerImage:getHeight() listener.x = 320 listener.y = 240 listener.angle = 0 sound = love.audio.newSource("bing.wav", "static") -- the "static" tells LÖVE to load the file into memory, good for short sound effects sound:setDirection( 0, 1, 0 ) -- "down" -- setup listener (not working on macosx at least) love.audio.setOrientation ( 0,-1,0, 0,0,1 ) -- forward and up vectors love.audio.setPosition ( listener.x, listener.y, 0 ) love.audio.setVelocity ( 0, 100, 0 )end

function love.mousepressed( x, y, button ) sound:stop() -- set source position (doesn't seem to work on macosx?) sound:setPosition ( x, y, 0 ) sound:setPitch ( y / 240.0 ) sound:setVolume ( x / 320.0 ) sound:play()end

function love.draw() love.graphics.setColorMode("replace") love.graphics.draw(listener.listenerImage, listener.x, listener.y, math.rad(listener.angle), 1, 1, listener.w/2, listener.h/2)end

Lua

•can run under embedding application (Love)

•can run standalone (lua)

•good for experimenting, learning

chunks• sequence of lua statements

• needs no separator between consecutive statements

• line breaks ignored

• can be read from interactive console

• can be read from a file

• both: lua -i filename

• starts up console after running chunk from filename

identifiers• string of letters, digits, underscores

• starts with letter or underscore

• dont’ use names like _VERSION

• case sensitive

• dont use reserved words:

• and end break in repeat while false local return do for nil then else function not true elseif if or until

comments•single line comment: starts with -- (2

hyphens)

•block comments

• --[[

• --]]

• (disable by adding a hyphen at front of opening comment ---[[ is just a single line comment)

Types and Values• Lua is dynamically typed

• no type definitions

• each value carries a type

• 8 basic types:

• nil, boolean, number, string, userdata, function, thread, table

• the type() function returns a string with the type’s name

• print( type(“Hello World”) )

• print ( type(10.4*3))

Nil•a type with a single value, nil

•a “non-value” meaning “no useful value”

•different from every other value

•globals are nil by default (before assignment)

•delete a variable by assigning nil to it

•return nil

Booleans

•two values: true and false

•conditionals consider nil and false as false

•anything else (including 0, “”) is true

Numbers

•double-precision floating-point

•no rounding errors with integers < 10^14

•ex) 4 3.1543 6.25e23 100e-3

Strings• sequence of characters

• can contain any embedded code, incl zero

• immutable - can’t change strings, just create new ones with changes

• a = “one string”

• b = string.gsub(a, “one”, “another”0

• print (a)

• print (b)

• can use single or double quotes

• can include C-like escape sequences (\n, \t, etc)

• can also use [[ and ]] to delimit multi-line strings

strings• any numeric operation applied to a string tries to convert the string

to a number

• print (“10” + 1) -- prints 11

• if a number is given when a string is expected, lua tries to convert it

• print(10 .. 20 ) -- prints 1020

• .. operator is string concatenation

• best to do explicit coercion

• tonumber(string)

• tostring(number)

• get string length with the length operator, #

• a = “hello”

• print(#a)

Tables

•associative arrays -- indexed with any value except nil

•the ONLY data structure in lua

•used for arrays, sets, records, queues, etc.

•tables are objects

table examplesa = {} -- creates an empty table

k = “x”

a[k] = 10

a[20] = “cool”

print(a[“x”]) --> 10

k = 20

print(a[k]) --> “cool”

a[“x”] = a[“x”] + 1

print(a[“x”]) --> 11

tables• tables grow as needed to hold new values

• a.name is syntactic sugar for a[“name”]

• not a[name] !!!

• lua convention: arrays start at 1!

• # gives last index (size) of table (doesn’t count holes...)

for i = 1,#a do

print (a[i])

end

functions

•first-class values

•can store in variables,

•can pass as arguments to other functions

•can be returned from functions

•“proper lexical scoping” of nested functions

userdata and threads

•userdata - for arbitrary C data in lua variables

•threads - coroutines(?)