How do I use physics.joint?

Questions
1

I was playing with balls (http://codea.io/talk/discussion/6714/playing-with-balls) using physics and wanted to use joints on them like the one on physics lab. I tried to look up on how they work but I understood none so far. I also tried playing around with them but it doesn’t work. :frowning:

2

Here’s a simple example of 2 joints.

supportedOrientations(PORTRAIT_ANY)
displayMode(FULLSCREEN)

function setup()
    speed=470
    c1 = physics.body(CIRCLE,0)
    c1.x = 400
    c1.y = 900
    c1.restitution = 1
    c1.type = STATIC    
    c2 = physics.body(CIRCLE,25)
    c2.x = 400
    c2.y = 600
    c2.restitution = 1      
    c3 = physics.body(CIRCLE, 25)
    c3.x = 400
    c3.y = 800
    c3.linearVelocity=vec2(speed,0)
    c3.restitution = 1      
    joint1 = physics.joint(REVOLUTE,c1,c2,c1.position)
    joint2 = physics.joint(REVOLUTE, c2, c3,c2.position)   
end

function draw()
    background(40, 40, 50)
    fill(255)
    noFill()     
    stroke(255)
    strokeWidth(2)
    line(c1.x,c1.y,c2.x,c2.y)
    line(c2.x,c2.y,c3.x,c3.y) 
    ellipse(c1.x,c1.y,2)        
    ellipse(c2.x,c2.y,c2.radius*2)     
    ellipse(c3.x,c3.y,c3.radius*2) 
end
3

@xvine Here’s a stripped down version of the above code. I removed all the code that wasn’t needed. This should be easier to understand joints.

supportedOrientations(PORTRAIT_ANY)
displayMode(FULLSCREEN)

function setup()
    c1 = physics.body(CIRCLE,0)
    c1.x = 400
    c1.y = 1000
    c1.type = STATIC    
    c2 = physics.body(CIRCLE,25)
    c2.x = 700
    c2.y = 700
    c3 = physics.body(CIRCLE, 25)
    c3.x = 600
    c3.y = 900
    joint1 = physics.joint(REVOLUTE,c1,c2,c1.position)
    joint2 = physics.joint(REVOLUTE, c2, c3,c2.position)   
end

function draw()
    background(40, 40, 50)
    noFill()     
    stroke(255)
    strokeWidth(2)
    line(c1.x,c1.y,c2.x,c2.y)
    line(c2.x,c2.y,c3.x,c3.y) 
    ellipse(c2.x,c2.y,c2.radius*2)     
    ellipse(c3.x,c3.y,c3.radius*2) 
end
4

Thanks @dave1707, it helped me a lot :slight_smile: