unity - how to make a 2D canvas follow NPC in 3D world space?

Question

I'm trying to create an emoji balloon like this:

My NPC is walking at a 3D world space, but the canvas should be a 2D fixed image, following above characters head. In my case I need it to be clickable.

Should I use some specific kind of Camera Overlay or screen spaces?

I'm using Ortographic camera.

Answer 1

As mentioned you could either use a world space Canvas and then parent it and make it always face the camera (billboard).

---

Or you could also stay in Screenspace Overlay and just make your object follow the NPC using Camera.WorldToScreenPoint

public enum OffsetType
{
    Screenspace,
    Worldspace
}

public class FollowTargetInScreenSpace : MonoBehavior 
{
    public Transform Target;

    [SerializeField] private Camera camera;

    public OffsetType OffsetType;

    public Vector3 Offset;

    private void Awake()
    {
        if(!camera) camera = Camera.main;
    }

    private void Update()
    {
        if(!Target) return;

        var worldPosition = Target.position;

        Vector2 screenPoisition;

        switch(OffsetType)
        {
            case OffsetType.Screenspace:
                screenPoisition = camera.WorldToScreenPoint(worldPosition) + (Vector2) Offset;
                break;

             case OffsetType.Worldspace:
                 screenPoisition = camera.WorldToScreenPoint(worldPosition + Offset);
                 break;

             default:
                 throw new ArgumentOutOfRangeException(nameof(OffsetType));         
        }

        transform.position = screenPoisition;
    }
}