Help to update vertices in Bodies.fromVertices without moving the position of the polygon

[Cesar89]

Hello, Im working in a videogame made with MatterJS,

Im using Bodies.fromVertices to create an irregular polygon.
Its vertices should be dynamic, so should change in time.
I already have the values of the new vertices in each frame, so I only need to set it to the polygon.
"Body.setVertices" didn't work for me, so the only way I found to do that was removing the polygon and creating another one with the new vertices, in the same position, for each frame.

All is working smoothly except for the position of the polygon.

The position is generated around the center of mass, but im not sure how that center is calculated, and its impossible to me to have the polygon always in the same position, it moves chaotically everywhere when I change the vertices.
I tryied by calculating the width/height of the polygon with the bounds.min/max/.x/.y, and move it but its now working, i think because the polygon can take any shape, you never know where will be positioned and how to compensate for that movement.

Do you know if there is another way to set the new vertices without remove/create the previous polygon, or if there is any way to get this work as it is?

This is the code where I remove the previous polygon, and I add the new one. The variable "vert" have new vertices each frame. "xPos" and "yPos" is where i want the polygon, this value never changes but the polygon is moving anyway.

Composite.remove(engine.world, groundFromVertices);
groundFromVertices = Bodies.fromVertices(xPos, yPos, vert, {isStatic : true, 
      render: {
           fillStyle: 'red',  
           strokeStyle: 'white',
           lineWidth: 5
      }}, false, 0, 0, 0, 0);
Composite.add(engine.world, groundFromVertices);

I think this is a question instead of an issue, but i dont know how to put it as a question, sorry about that.
Thank you so much in advice

[poakey1]

@Cesar89 I know it's late but hope this helps.
var centreOfMass = Vertices.centre(yourVertices);

[Cesar89]

@poakey1 Thank you so much. I managed to make the polygon to keeps its position, but now when some body interacts with it, the physics are not ok. Its like the body were floating above the polygon.

I reproduced it in this codepen:
https://codepen.io/himu89/pen/xxJdVyP

Thank you for your help