I’ve been playing around with the physics.joint commands and have a problem. I can’t get the DISTANCE joint to work properly. Here is an example showing what I ran into. The rectangle is locked into a PRISMATIC joint with a point in the center of the screen and can only move right or left. The circle is KINEMATIC and able to move up, down, left, or right. The circle and rectangle are locked together with the DISTANCE joint. So as the circle moves right or left, it either pushes or pulls the rectangle with it because of the joint between them. But if the circle moves up or down, strange thing happen. What I think should happen is, as the circle moves up or down the connecting point of the rectangle should move left so it’s either directly above or below the circle as the DISTANCE joint gets stretched. When the circle moves down, the rectangle starts to move correctly to the left, but after awhile it moves right and starts to oscillate. When the circle goes up, the rectangle moves right and starts to oscillate. Press a button to make the circle move in a direction. Restart the program between key presses. @Simeon, can you look at this. Is there a problem with the joint or am I doing something wrong.

EDIT: The DISTANCE joint requires 4 parameters. I originally had it as REVOLUTE and changed it to DISTANCE without realizing I needed to add another parameter. The below code was updated and now works correctly.

```
displayMode(FULLSCREEN)
function setup()
rectMode(CENTER)
dx=0
dy=0
-- center point
c1=physics.body(CIRCLE,0)
c1.x=WIDTH/2
c1.y=HEIGHT/2
c1.type=STATIC
-- moving circle
c2=physics.body(CIRCLE,0)
c2.x=WIDTH/2-200
c2.y=HEIGHT/2
c2.type=KINEMATIC
-- rectangle
s2=physics.body(POLYGON,vec2(0,-15),vec2(0,15),
vec2(100,15),vec2(100,-15),vec2(0,-15))
s2.x=WIDTH/2
s2.y=HEIGHT/2
-- joint to lock rectangle into right or left movement with c1 point
j1=physics.joint(PRISMATIC,c1,s2,c1.position,vec2(1,0))
-- joint to lock moving circle c2 and rectangle s2 together
j2=physics.joint(DISTANCE,c2,s2,c2.position,s2.position)
end
function draw()
background(40, 40, 50)
noFill()
stroke(255)
strokeWidth(2)
-- draw point, circle and rectangle
ellipse(c1.x,c1.y,5)
ellipse(c2.x,c2.y,20)
drawPoints(s2)
-- draw connection between c2 and s2
line(j2.bodyA.x,j2.bodyA.y,j2.bodyB.x,j2.bodyB.y)
-- change velocity of c2
c2.linearVelocity = vec2(dx,dy)
-- draw buttons
rect(WIDTH/2,HEIGHT-200,100,50)
rect(WIDTH/2,200,100,50)
rect(100,HEIGHT/2,100,50)
rect(WIDTH-100,HEIGHT/2,100,50)
fill(255,0,0)
text("UP",WIDTH/2,HEIGHT-200)
text("DOWN",WIDTH/2,200)
text("LEFT",100,HEIGHT/2)
text("RIGHT",WIDTH-100,HEIGHT/2)
end
function drawPoints(s)
-- draw lines for rectangle
for z=2,#s.points do
line(s.x+s.points[z-1].x,s.y+s.points[z-1].y,
s.x+s.points[z].x,s.y+s.points[z].y)
end
end
function touched(t)
if t.state==BEGAN then
dx=0
dy=0
-- check which button was pressed
if t.x>WIDTH-150 and t.x<WIDTH-50 and
t.y>HEIGHT/2-25 and t.y<HEIGHT/2+25 then
dx=30
end
if t.x>50 and t.x<150 and
t.y>HEIGHT/2-25 and t.y<HEIGHT/2+25 then
dx=-30
end
if t.x>WIDTH/2-50 and t.x<WIDTH/2+50 and
t.y>150 and t.y<250 then
dy=-30
end
if t.x>WIDTH/2-50 and t.x<WIDTH/2+50 and
t.y>HEIGHT-225 and t.y< HEIGHT-175 then
dy=30
end
end
end
```