Playing with balls

Code Sharing
1

This is the first project I have worked on in Codea. It’s a simple project that shows balls and stuff. :>


--# Main
-- Ball Test 3 (complete)

function setup()
    
    parameter.boolean("add", false) -- For adding balls
    parameter.boolean("stat",true)  -- Makes a newly made ball move
    parameter.boolean("pchange",true)   -- Set to false if you don't want to change the ball you want to move
    parameter.boolean("psize",false)    -- Set to true if you want to change the size your ball
    parameter.integer("pspeed",0,10,1)  -- The amount of force exerted on your ball is multiplied by this value + 1
    parameter.integer("size",1,100,30)  -- Sets the size of a newly made ball or your ball
    parameter.action("Stop Player Movement", function() -- Stops the movement of your ball
        for k,v in pairs(b) do
            if v.player then
                v.linearVelocity = vec2(0,0)
            end
        end
    end)
    parameter.action("Stop all ball movement", function() -- Stops the movement of all balls
        for k,v in pairs(b) do
            v.linearVelocity = vec2(0,0)
        end
    end)
    
    b = {}  -- Store all the bodies here
    
    -- Walls
    local floor = physics.body( EDGE, vec2(0, 0), vec2(WIDTH, 0))
    floor.restitution = 1.1
    
    local left = physics.body( EDGE, vec2(0, 0), vec2(0, HEIGHT))
    left.restitution =  1.1
    
    local right = physics.body( EDGE, vec2(WIDTH, 0), vec2(WIDTH, HEIGHT))
    right.restitution = 1.1
    
    local ceiling = physics.body( EDGE, vec2(0, HEIGHT), vec2(WIDTH, HEIGHT))
    ceiling.restitution = 1.1
    
    physics.gravity(0,0)    -- Tabletop physics
    physics.continuous = true   -- Balls don't pass through walls if they get too fast
    
    table.insert(b,floor)
    table.insert(b,left)
    table.insert(b,right)
    table.insert(b,ceiling)
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
    strokeWidth(2)
    
    -- Do your drawing here
    for k,v in pairs(b) do  -- Draws the balls
        drawBodies(v)
        if v.player and psize then  -- Changes the size of your ball if psize
            v.radius = size
        end
    end
    
    if explode then -- Shows the last contact / Nice effects
        sprite("Space Art:Red Explosion", exp.x, exp.y, exps, exps) -- exps is the energy of the impact
    end
end

function touched(touch)
    t = vec2(touch.x, touch.y)
    if touch.state == BEGAN then
        if add then -- Makes a ball if add
            makeCirc(t.x,t.y)
        else
            for k,v in pairs(b) do
                if v.shapeType == CIRCLE and not pcheck(v) and v.player then
                    v:applyForce((t-v.position)*(pspeed+1)) -- Applies force
                end
            end
        end
    end
end

function collide(contact)
    if contact.state == BEGAN then
        exp = contact.position
        exps = contact.normalImpulse
        explode = true
        tween.delay(0.1, function()
            explode = false
        end)
        sound(DATA, "ZgNAFQBJQEBAQEBAAAAAAAAAAAC5ZIg+AABAf0BAQEBAQHJx")
    end
end

function makeCirc(x,y)
    local a = physics.body(CIRCLE,size)
    a.x, a.y = x, y
    a.restitution = 1
    a.interpolate = true
    a.player = false
    if not stat then
        a:applyForce(vec2(math.random(-1000,1000),math.random(-1000,1000)))
    end
    table.insert(b, a)
end

function drawBodies(obj)
    pushStyle()
    fill(255, 0, 0, 0)
    stroke(25, 255, 0, 165)
    if obj.shapeType == EDGE then
        line(obj.points[1][1],obj.points[1][2],
        obj.points[2][1],obj.points[2][2])
    elseif obj.shapeType == CIRCLE and obj.player then
        pushStyle()
        noStroke()
        fill(0, 255, 180, 255)
        ellipse(obj.x,obj.y,obj.radius*2)
        popStyle()
    elseif obj.shapeType == CIRCLE then
        ellipse(obj.x,obj.y,obj.radius*2)
    end
    popStyle()
end

function pcheck(obj)    -- Checks if a tap is inside a ball
    if pchange and t:dist(obj.position)<=obj.radius then
        for k,v in pairs(b) do
            v.player = false
        end
        obj.player = true
        return true
    else
        return false
    end
end
2

Please show ways to make it better. :slight_smile:

3

Nice work for a first project

--instead of 
if tx >= obj.x - obj.radius and tx <= obj.x + obj.radius 
    and ty >= obj.y - obj.radius and ty <= obj.y + obj.radius 
    and pchange == true then

--try this
--dist is the distance between two vectors (points)
if pchange and vec2(tx,ty):dist(obj)<=obj.radius then
4

It’s actually the 3rd version of the project. The first project only has the creation of balls and the second one is just a fancier version of the first.

I don’t understand the code you just posted.
By the way, your ebook helped me a lot :slight_smile:

Edit:
I understood it but it gives me an error.

Edit2:
Eureka! Apparently, it doesn’t work when you just put obj inside.

    if pchange and vec2(tx,ty):dist( vec2(obj.x, obj.y) )<=obj.radius then

Just updated the code.

5

ah, yes, I overlooked that obj wasn’t a vec2

it’s worth looking at the other vector functions in Codea, they can be very helpful. If you make your position variables vec2’s, then it makes using those functions a little easier (and your code a little tidier)

--if your position is t [=vec2(x,y)], instead of tx,ty
--and your object position is obj.pos instead of obj.x and obj.y
--and both of those are vec2, then you have
if pchange and t:dist(obj.pos) )<=obj.radius then

and your “apply force” line

v:applyForce(vec2((tx-v.x)*(pspeed+1), (ty-v.y)*(pspeed+1)))
--can be written as
v:applyForce((t-v)*(pspeed+1))

(PS thanks for the kind words about the ebook).

6

Actually

if tx >= obj.x - obj.radius and tx <= obj.x + obj.radius 
    and ty >= obj.y - obj.radius and ty <= obj.y + obj.radius 
    and pchange == true then

and

if pchange and vec2(tx,ty):dist(obj)<=obj.radius then

are not equivalent. (But the second is probably what you want anyway.)

7

Thanks @Ignatz, I looked at the touched function and noticed that I could shorten the if statements into one if statement. I also made tx and ty into a vec2 in order to shorten other parts of my code.

@LoopSpace I don’t understand why they are not equivalent, could you please explain why

8

They are not equivalent because my code assumes your objects are circular, whereas your original code worked for squares.

But I thought you probably wanted circles (and even if you have squares, it is close enough, since we have fat fingers that don’t touch accurately).

9

Thanks, I get it now. (Fat fingers :)))

I also noticed that instead of putting “== true”, you could just write the variable/function. It also works with “== false” by putting “not” before the variable/function.

if var == true then

-- Just write
if var then


-- Instead of
if var == false then

-- Just write
if not var then
10

That’s right.

A very good trick is using or to set defaults for variables, eg in a function like this

function ABC(a,b)
   --if a is nil or not provided, use 10
   a = a or 10 
   --if b is nil or not provided, use 0.15
   b = b or 0.15 
    return a,b
end

--then 
ABC() --> returns 10, 0.15
ABC(3) --> returns 3, 0.15
ABC(nil,2) --> returns 10, 2
11

@Ignatz Thanks for the info :smiley:
I also thank you very much for your ebooks, I started reading the lua ebook before I even knew about Codea and it helped me a ton. :smiley: