Rigidbody.ClosestPointOnBounds

Наиболее близкая точка к предельной решетке присоединенных коллайдеров.

// Subtract damage from a character's hit points when an
// explosion occurs.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public float hitPoints = 10.0F;
    public Rigidbody rb;

    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    void ApplyDamage(Vector3 explosionPos, float radius)
    {
        Vector3 closestPoint = rb.ClosestPointOnBounds(explosionPos);
        float distance = Vector3.Distance(closestPoint, explosionPos);
        float damage = 1.0F - Mathf.Clamp01(distance / radius);
        damage *= 10;
        hitPoints -= damage;
    }
}