RoamBetweenPoints.cs

using UnityEngine;
using System.Collections;

public class RoamBetweenPoints : MonoBehaviour {

	public Transform[] targets;
	public LayerMask groundLayer;

	private Transform target;
	private NavMeshAgent agent;

	private Quaternion smoothTilt;

	void Start () {
		agent = GetComponent<NavMeshAgent>();
		smoothTilt = new Quaternion();
	}

	void Update () {
		float distanceToTarget = 0;

		if(target != null){
			distanceToTarget = Vector3.Distance(transform.position, target.position);
		}

		if(distanceToTarget < 5){
			int randomIndex = Random.Range(0,(targets.Length));
			target = targets[randomIndex];
			agent.SetDestination(target.position);
		}

		RaycastHit rcHit;
		Vector3 theRay = transform.TransformDirection(Vector3.down);
		
		if (Physics.Raycast(transform.position, theRay, out rcHit, groundLayer))
		{
			float GroundDis = rcHit.distance;
			Quaternion grndTilt = Quaternion.FromToRotation(Vector3.up, rcHit.normal);

			smoothTilt = Quaternion.Slerp(smoothTilt, grndTilt, Time.deltaTime * 2.0f);

			Quaternion newRot = new Quaternion();
			Vector3 vec = new Vector3();
			vec.x = smoothTilt.eulerAngles.x;
			vec.y = transform.rotation.eulerAngles.y;
			vec.z = smoothTilt.eulerAngles.z;
			newRot.eulerAngles = vec;

			transform.rotation = newRot;

			Vector3 locPos = transform.localPosition;
			locPos.y = (transform.localPosition.y - GroundDis);
			transform.localPosition = locPos;
		}
	}
}