Physiycs.body EDGE .position?

Questions
1

Hello. Im confused about what .position does for an EDGE physics body. Its a vec2 and not a vec4 which seems odd especially when you set the original pos in 2 vec2s. Can someone please alleviate my confusion?

2

@Goatboy76 - I’m guessing position doesn’t do anything for an EDGE, and you should just ignore it.

3

@Goatboy76 take the position as an average of both vec2s?

4

@Ignatz I know that it does soemthing because when I set it the EDGE is not where it used to be vs if I dont set the position.

5

@Goatboy76 - maybe that’s true, but why on earth are you setting position for EDGE? Just ignore it. It’s meant to be used by other physics objects like circles.

6

@Luatee That would work to get that pos, but to set it? Why not let the user average it instead of bottle necking it there.

7

@Ignatz Im probley using the wrong type. EDGEs aren’t meant to be moved? I wanting to have a “wall” that moves along a set path. Would chain be better?

8

Use a thin rectangle polygon instead of an edge to move it

9

@Coder Good idea

10

I tried to wright an example of @Coder 's idea, but I’ve hit the same speed bump as before.
I cant find a way to get the pos of the rect. I feel like I’ve been down this road before but I probley deleted my example.

The block stops at -461 which makes me think that it is hitting the “floor” at the bottom of the screen and the starting pos for drawing it is wrong. But when I translate the drawing to the startingPos and it doesn’t quite line up.
Can someone please explain what is going on?

function setup()
    f1 = vec2(0,0)
    f2 = vec2(WIDTH,0)
    floor = physics.body(EDGE,f1,f2)
    
    rw1 = vec2(WIDTH,0)
    rw2 = vec2(WIDTH,HEIGHT)
    rw = physics.body(EDGE,rw1, rw2)
    
    lw1 = vec2(0,0)
    lw2 = vec2(0,HEIGHT)
    lw = physics.body(EDGE,lw1, lw2)
    
    c1 = vec2(WIDTH, HEIGHT)
    c2 = vec2(0,HEIGHT)
    c = physics.body(EDGE,c1, c2)
    
    w = 100
    local pos = vec2(WIDTH/2, HEIGHT/2)
    rec = physics.body(POLYGON, vec2(pos.x - w/2, pos.y - w/2), vec2(pos.x + w/2, pos.y - w/2),
                                vec2(pos.x - w/2, pos.y + w/2), vec2(pos.x + w/2,pos.y + w/2))
    rec.type = DYNAMIC
    
    -- rec.type = STATIC
    -- rec.position = vec2(pos.x, pos.y)
    print(rec.position)

end


function draw()
    print(rec.position)
    background(40, 40, 50)
    
    fill(224, 26, 26, 255)
    local pos = rec.position
    --  translate(startPos.x, startPos.y)
    rect(pos.x, pos.y, w, w)

end
11

Add WIDTH/2 and HEIGHT/2 to the pos in rect()

12

@Luatee Do you know why the rect stops short of the bottom and kind gitters when it stops?

13

@Goatboy76 Try this.


function setup()
    rectMode(CENTER)
    f1 = vec2(0,0)
    f2 = vec2(WIDTH,0)
    floor = physics.body(EDGE,f1,f2)

    rw1 = vec2(WIDTH,0)
    rw2 = vec2(WIDTH,HEIGHT)
    rw = physics.body(EDGE,rw1, rw2)

    lw1 = vec2(0,0)
    lw2 = vec2(0,HEIGHT)
    lw = physics.body(EDGE,lw1, lw2)

    c1 = vec2(WIDTH, HEIGHT)
    c2 = vec2(0,HEIGHT)
    c = physics.body(EDGE,c1, c2)

    w = 100
    local pos = vec2(WIDTH/2, HEIGHT/2)
    rec = physics.body(POLYGON, vec2(-w/2,-w/2),vec2(w/2,-w/2),
                                vec2(w/2,w/2), vec2(-w/2,w/2))
    
    rec.x=300
    rec.y=600
end


function draw()
    print(rec.position)
    background(40, 40, 50)

    fill(224, 26, 26, 255)
    --local pos = rec.position
    --  translate(startPos.x, startPos.y)
    rect(rec.x,rec.y, w, w)
end
14

@dave1707 Thanks for your help. My mistake was not knowing you set the points with the origin at the pos. Thanks eveyone!

15

@Goatboy76 Depending on whether you want the reference at a corner or the center of the rect, it’s easier do it using the origin.