how to combine meshes and get click location with respect to main parent in c# using unity

Question

Let's say I have a 3D tower in Unity. The tower is structured such that a Transform parent has children where each child represents a floor of the tower. The children themselves are an empty game object (only component is a Transform) and they are the parent of many (custom) meshes (each grandchild is a separate custom mesh). How do I combine those meshes so that I can click somewhere on a floor of the tower and then get the coordinates of that click with respect to the tower as a whole/local position in the tower?

Answer 1

I would have a dedicated class on the root like

public class Tower : MonoBehaviour { }

then you can have a MeshCollider (or any Collider but of course you will get the position on the collider not the displayed mesh) on all children and do

// Get a ray of your click position
var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
// Shoot a raycast
if(Physics.Raycast(ray, out var hit))
{
    // Try to get the Tower component of the parent
    // bubbles up until it finds according component or returns null
    var tower = hit.gameObject.GetComponentInParent<Tower>();
    // Are we clicking at any child under a Tower component?
    if(tower)
    {
        // get the hit point in world space
        var worldPoint = hit.point;
        // Get the hit point relative to the tower's pivot
        var relativePoint = tower.transform.InverseTransformPoint(worldPoint);

        Debug.Log($"You have hit tower at {relativePoint.ToString("G9")}");     
    }
}

See

• Camera.main
• Camera.ScreenPointToRay
• Physics.Raycast
• GameObject.GetComponentInParent
• RaycastHit.point
• Transform.InverseTransformPoint