Distance based item interaction

Question

I'm having an odd issue in my implementation of distance based object interaction in Unity. Basically it's a simple "Press [key] to [search/pickup/open/etc]" function which requires the player to be within a certain distance of the object before interaction is allowed (via mouse over). In my scene I have 2 test objects which I have set up as similarly as possible, but they are acting differently and I cannot seem to work out why. * http://imgur.com/a/hoAIH * http://imgur.com/a/HbvrO These are the setups, and the script which is on both parent objects is as follows:

public class DisplayUI : MonoBehaviour
{
    public string itemName;
    bool isSelected;
    bool isNear;

    void OnTriggerEnter(Collider col)
    {
        isNear = true;
    }

    void OnTriggerExit(Collider col)
    {
        isNear = false;
    }

    void OnMouseOver()
    {
        if (isNear)
            isSelected = true;
        else
            isSelected = false;
    }

    void OnMouseExit()
    {
        isSelected = false;
    }

    void OnGUI()
    {
        if(isSelected == true)
        {
            GUI.Label(new Rect(Screen.width / 2, Screen.height / 2, 200, 20), "Press E to search " + itemName);
        }
    }
}

For some reason the sphere/cube game object is acting as desired where the mouseover detects the edge of each mesh perfectly, and relies on the distance (within the trigger collider) too, creating the gui label as coded. The trash can however seems to think the main trigger collider is the edge of the mesh so even when the mouse is way outside the physical mesh, the gui label is showing. Where am I going wrong with this?

Answer 1

Your object Trash1 has two non-triggering colliders attached to it: A Box Collider and a Mesh Collider. The OnMouseOver and OnMouseExit events will take both of them into account. So the OnMouseOver event gets fired when the mouse is over the BoxCollider which surrounds the model.

Your Sphere1 also has two colliders, but in this case they are a Sphere Collider and a Mesh Collider which have almost the same shape, so the problem is not noticeable. But it's still a slight performance hook (not noticeable in such a simple scene but it could become problematic when you have a lot of these).

I don't know why you attached two colliders to your objects, but it seems to me like one for each of them would suffice. In general you should prefer the "Geometric Object" colliders over Mesh Colliders because they are far more performance-friendly (especially when the mesh colliders are directly derived from high-polygon models and not based on simplified versions). But in the case of the trash can you have no choice because there is no optimized "Cylinder Collider" in Unity.

Answer 2

You could use a vector 3 to check if the object is near.

Example:

if (Vector3.Distance ( "Put your player here".transform.position, "Put object to check for here".position) < 5) 
{
    "Block of code here"
}