Smart missile that detects terrain

Hi
I have the script below to fly a missile towards my plane and destroy it. That's great. But.. the missile flies directly into the terrain if there is a hill in the way. How can I make it smart and have it smoothly fly over terrain mountains to get to the target. It would also need to rotate on its axis when going up a mountain for eg.
I was going to use something like this..

terrainHeightWhereWeAre = Terrain.activeTerrain.SampleHeight( transform.position );
if (terrainHeightWhereWeAre > transform.position.y) {
transform.position = new Vector3 (transform.position.x,
terrainHeightWhereWeAre,
transform.position.z);

But for some reason transform.position.y is 0 when i read it's value ?

any help would be great.
Thanks!




using UnityEngine;
using System.Collections;

public class missile_follow: MonoBehaviour {


public float hover = 0.0f;
public float terrainHeightWhereWeAre = 0.0f;
public string searchTag;
private GameObject closetMissle;
private Transform target;
public GameObject missileExpObject;

void Start()
{
closetMissle = FindClosestEnemy();

if(closetMissle)
target = closetMissle.transform;
}

void Update()
{

if(target == null)
{
closetMissle = FindClosestEnemy();

if(closetMissle)
{
target = closetMissle.transform;
}
}


transform.LookAt(target);
transform.Translate(Vector3.forward * 280.0f * Time.deltaTime);
}

GameObject FindClosestEnemy()
{
GameObject[] gos;
gos = GameObject.FindGameObjectsWithTag(searchTag);

GameObject closest = null;
float distance = Mathf.Infinity;


// terrainHeightWhereWeAre = Terrain.activeTerrain.SampleHeight( transform.position );




Vector3 position = transform.position ;


terrainHeightWhereWeAre = transform.position.y;

foreach(GameObject go in gos)
{
Vector3 diff = go.transform.position - position ;
float curDistance = diff.sqrMagnitude;

if(curDistance < distance)
{
closest = go;
distance = curDistance;
}
}

return closest;
}
void OnTriggerStay(Collider otherObject)
{
if(otherObject.tag == "Enemy") //&& playerEntered)
{

var expPrefab = Instantiate(missileExpObject, this.transform.position, Quaternion.identity);
Destroy (this.gameObject);
Destroy(otherObject.gameObject);
//Player.Score +=100;
print ("explode enemy");
}


}

}

 

Try Raycasting in front the direction it is heading and if it sees the terrain, have it adjust it's path up

 

Thanks mate, that put me on the right track

 

Take a look at navmesh. Or A* pathfinding plugin (which is free)