# Kangaroo object are solved but appear to be moving because of one vector

I have an assembly of random object that are grouped by some springs and rigid bodies and a custom goal for lines keeping them parallel. Without my goal the simulations solves in around 700 iterations but when I use it it solves also fast but then starts floating in space. I think its because it could not converge for some of the vectors I used in my goal:

So my question is how do I compensate for this behaviour? Because it solves for all lines in the end do I have to set some kind of threshold that would deem the solution as successful? I tried with a simple counter but doesnâ€™t seem to be reasonable.

``````      b1 = b2 = b3 = true;
var angle = Math.Abs(Lim) * Math.PI / 180;

//var c1 = Vector3d.CrossProduct(mVV1, mV1);
var a1 = Vector3d.VectorAngle(mVV1, mV1);
if (Math.Abs(a1) > angle )
{
Move[6] = m12 - m2;
Weighting[6] = Strength;
}
else
{
Move[6] = Vector3d.Zero;
Weighting[6] = 0.0;
b1 = false;
}

var a2 = Vector3d.VectorAngle(mVV2, mV2);
if (Math.Abs(a2)  > angle)
{
Move[8] = m32 - m4;
Weighting[8] = Strength;
}
else
{
Move[8] = Vector3d.Zero;
Weighting[8] = 0.0;
b2 = false;
}

var a3 = Vector3d.VectorAngle(mVV3, mV3);
if (Math.Abs(a3) > angle)
{
Move[10] = m52 - m6;
Weighting[10] = Strength;
}
else
{
Move[10] = Vector3d.Zero;
Weighting[10] = 0.0;
b3 = false;
}

if (b1 == false && (b2 == false & b3 == false))
if (b1 == _b1 && (b2 == _b2 && b3 == _b3))
counter++;

//      if (counter > 20)
//      {
//        Move[10] = Move[8] = Move[6] = Vector3d.Zero;
//        Weighting[10] = Weighting[8] = Weighting[6] = 0.0;
//      }

_b1 = b1;
_b2 = b2;
_b3 = b3;
``````

Hi @ankere
I canâ€™t figure out whatâ€™s happening here from this bit of code.
If you want to post the definition (or send it to me if you donâ€™t want to post it here) Iâ€™ll take a look.
Also - if what is needed is to keep pairs of lines parallel, you can use the Angle component with an angle of 0. (the segments do not need to share a point)

1 Like

Hello @DanielPiker

I would prefer to use a PM if you are OK with it? I will send a message with two of my papers that are not open access yet as it can clarify things up. I will attach a definition as well. Message title is â€śTriangle definition questionâ€ť.

The angle goal did not work for me or at least I could not make it work because one of the lines must be defined and change during the steps of the solution.