Collider.ClosestPointOnBounds  

function ClosestPointOnBounds (position : Vector3) : Vector3

Description

The closest point to the bounding box of the attached collider.

This can be used to calculate hit points when applying explosion damage.

var hitPoints : float = 100.0;
function ApplyHitPoints (explosionPos : Vector3, radius : float) {
    // The distance from the explosion position to the surface of the rigidbody
    var closestPoint : Vector3 = collider.ClosestPointOnBounds(explosionPos);
    var distance : float = Vector3.Distance(closestPoint, explosionPos);

    // The hit points we apply fall decrease with distance from the hit point
    var hitPoints : float = 1.0 - Mathf.Clamp01(distance / radius);
    
    // This is the final hitpoints we want to apply. 10 at maximum
    hitPoints *= 10;
}