Semi-circle physics body

Questions
1

Is it at all possible to create a physics body that has a flat bottom with a semi-circle top to it? I’m relatively new to physics programming. Thanks in advance.

2

@TheHam Yes. Use POLYGON and create the semi-circle with a bunch of vec2 values.

3

@TheHam Here’s an example of a semi-circle physics body.

displayMode(FULLSCREEN)

function setup()
    physics.continuous=true
    e1=physics.body(EDGE,vec2(0,0),vec2(WIDTH,0))
    e2=physics.body(EDGE,vec2(0,0),vec2(0,HEIGHT))
    e3=physics.body(EDGE,vec2(WIDTH,0),vec2(WIDTH,HEIGHT))
    e4=physics.body(EDGE,vec2(0,HEIGHT),vec2(WIDTH,HEIGHT))
    sim={}
    for z=0,180,1 do
        x=math.cos(math.rad(z))*100
        y=math.sin(math.rad(z))*100
        table.insert(sim,vec2(x,y))
    end
    s=physics.body(POLYGON,unpack(sim))
    s.x=300
    s.y=300
    s.restitution=1
    s.friction=0
    b=physics.body(CIRCLE,30)
    b.x=250
    b.y=HEIGHT-50
    b.restitution=1
    b.friction=0
    stroke(255)
    strokeWidth(2)
    fill(255)
end

function draw()
    background(40, 40, 50)
    pushMatrix()
    translate(s.x,s.y)
    rotate(s.angle)
    p=s.points
    j=#p
    for z=1,#p do
        line(p[j].x,p[j].y,p[z].x,p[z].y)
        j=z
    end
    popMatrix()
    ellipse(b.x,b.y,60)
end
4

I would increase the increment in the for loop to 5 or so: for z = 0,180,5 do. Gives Box2D and your draw loop a fifth the number of points to worry about.

5

Thanks guys, didn’t think of running a for loop, much appreciated.