How to get the 2d Poisition (in camera) of the mesh vertices

From each camera you should calculate the projection of the point on the screen using Camera.WorldToScreenPoint.

For intance:

 Vector3 ProjectFromCam1 = Camera1.WorldToScreenPoint(target.position);
 Vector3 ProjectFromCam2 = Camera2.WorldToScreenPoint(target.position);
 Vector3 ProjectFromCam3 = Camera3.WorldToScreenPoint(target.position);
 Vector3 ProjectFromCam4 = Camera4.WorldToScreenPoint(target.position);

After reading your question for the 5th time i guess all you want is:

• Transform.TransformPoint for converting the vertex positions into world space

• Camera.WorldToScreenPoint for projecting the world space positions into screenspace.

So a script like this should do what you want:

 // C#
 using UnityEngine;
 using System.Collections;
 
 public class MeshVertexPositions : MonoBehaviour
 {
     public Vector2[] Calculate2DPositions(Camera aCam)
     {
         Mesh m = null;
         var MF = Getcomponent<MeshFilter>();
         if (MF != null)
             m = MF.sharedMesh;
         var SMR = GetComponent<SkinnedMeshRenderer>():
         if (SMR != null) 
             m = SMR.sharedMesh;
         if (m == null)
             return null;
         Transform obj = transform;
         Vector3[] verts = m.vertices;
         Vector2[] result = new Vector2[verts.Length];
         for(int i = 0; i < verts.Length; +ii)
         {
             result[i] = aCam.WorldToScreenPoint(obj.TransformPoint(verts[i]));
         }
         return result;
     }
 }

If your character is made up of several meshes you have to do this for everyone.

Thanks for your replay and sorry for not being clear a lot, i'll try to be more clear - My object is a 3d human body - Suppose that i use only one camera (positionned in the scene to get the frontal picture) - I want to have the exact 2d positions (pixels) in this image that matches with the object vertices (to simplify, i say the 2d projection of all vertices in the screenshot). - i use the main camera with the default view (perspective) - i tried to use WorldToScreenPoint an print the 2d position i get on the picture, but the problem is that it dont give me the projection i wanted - the camera gives me this screenshot (picture1) - and when i print the vertices projection that i get like that Vector3 screenpose = Camera.main.WorldToScreenPoint(vertices[l])
it gives me the (picture2) - as you can see the 2d projection are not in the correct place thanks in advance