Quick Physics Example

Examples
1

Hello all,
Fooling around on a long car ride today, I came up with this:


--# addRect
addRect = class()

function addRect:init(x,y,endX,endY)
    -- you can accept and set parameters here
    local w,h = endX-x,endY-y
    self.body = physics.body(POLYGON,vec2(w/2,h/2),vec2(w/2,-h/2),vec2(-w/2,-h/2),vec2(-w/2,h/2))
    self.body.x = (x + endX)/2
    self.body.y = (y + endY)/2
    self.m = mesh()
    self.m.vertices = triangulate(self.body.points)
    self.m:setColors(255,255,255)
    self.body.fixedRotation = false
    self.body.friction = 0.2
    self.body.restitution = 0.0
    self.body.angle = 0
end

function addRect:draw()
    -- Codea does not automatically call this method
    pushMatrix()
    translate(self.body.x,self.body.y)
    rotate(self.body.angle)
    self.m:draw()
    popMatrix()
end

function addRect:touched(touch)
    -- Codea does not automatically call this method
end

--# Main
-- Creations testing

-- Use this function to perform your initial setup
function setup()
    print("Hello World!")
    objects = {}
    local a = generateWorld()
    m = mesh()
    m.vertices = triangulate(a)
    m:setColors(0,255,0)
    ground = physics.body(CHAIN,loop,unpack(a))
    touches = {}
    tId = nil
    initPos = nil
    noSmooth()
    frame = 1
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(40, 40, 50)

    -- This sets the line thickness
    noStroke()
    fill(255)

    -- Do your drawing here
    m:draw()
    if tId then
        if touches[tId].state==ENDED then
        objects[#objects+1] = addRect(initPos.x,initPos.y,touches[tId].x,touches[tId].y)
        tId = nil
        initPos = nil
        else
            rect(initPos.x,initPos.y,touches[tId].x-initPos.x,touches[tId].y-initPos.y)
        end
    end
    for i,v in pairs(objects) do
        v:draw()
    end
    text(math.floor(1/DeltaTime),WIDTH-10,HEIGHT-10)
    frame = frame + 1
end

function generateWorld()
    local verts = {}
    local control = math.random(0,100)
    for x=0,WIDTH, 5 do
        verts[#verts+1] = vec2(x,noise(x/100,control)*100+100)
    end
    verts[#verts+1] = vec2(WIDTH,verts[#verts].y)
    verts[#verts+1] = vec2(WIDTH,0)
    verts[#verts+1] = vec2(0,0)
    return verts
end

function touched(t)
    if not initPos and t.state==BEGAN then
        initPos = vec2(t.x,t.y)
        tId = t.id
    end
    touches[t.id] = t
end

Just a quick little example of using physics bodies, nothing too complicated. Sorry no documentation-I really should get around to that.
Psst-set friction to 100 and fixedRotation to true to have some fun :slight_smile:

2

@TheSolderKing Nice job. It doesn’t take much code to make interesting physics programs.

3

Thanks @dave1707! No it doesn’t indeed…Im thinking about making a game where you create vehicles and fight them against each other for the game jam–this is just a start of that. It’ll be multiplayer as well so that’ll be fun.

4

@TheSolderKing that’s pretty fun to play with

5

Thanks @Simeon! I had a great deal of fun making it and playing it. I was trying ot work on textures but oddly I cannot get them to work right now, but Ill keep at it and if I succeed Ill post the code above.

6

Looking forward to your game jam entry!

7

This is so cool!