navmesh and raycast obstacle avoidance

Hi all,

Ok so I ran up against this one and couldn't find any good/quick answers, so I cobbled something together. Figured I'd share (if for no better reason, than if I lose this, I can Google it again )

Basically, when you set the target (manually or through another script), Unity NavMeshAgent takes care of the usual navigation. If something gets hit by the raycast, a simple obstacle avoidance takes over. Once the obstacle is behind the character, the Unity NavMesh is switched back on.

Hope this helps someone else:

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5.  
6. /*
7.  * This script will use the Unity navmesh tools in combination with a simple
8.  * obstacle avoidance to navigate a map.  There is a lot of room for improvement,
9.  * but this does work.
10.  */
11. public class BaseCharacterwNav : MonoBehaviour {
12.     public Transform target; // where we're going
13.     private NavMeshAgent nma; // Unity nav agent
14.     public float probeRange = 1.0f; // how far the character can "see"
15.     private bool obstacleAvoid = false; // internal var
16.     public float turnSpeed = 50f; // how fast to turn
17.    
18.     // create empty game objects and place them appropriately infront, to the left and right of our object
19.     // This creates a little buffer around the character, and I had some trouble with never raycasting
20.     // outside the character rigidbody/collider
21.     public Transform probePoint; // forward probe point
22.     public Transform leftR; // left probe point
23.     public Transform rightR; // right probe point
24.    
25.     private Transform obstacleInPath; // we found something!  
26.    
27.     // Use this for initialization
28.     void Start () {
29.         nma = this.GetComponent<NavMeshAgent>();
30.         nma.SetDestination(target.position);
31.         if(probePoint == null)
32.             probePoint = transform;
33.         if(leftR == null) {
34.             leftR = transform;         
35.         }
36.         if(rightR == null)
37.             rightR = transform;        
38.     }
39.    
40.  
41.     void Update () {
42.        
43.         RaycastHit hit;
44.         Vector3 dir = (target.position - transform.position).normalized;
45. //     
46.         bool previousCastMissed = true; // no need to keep testing if something already hit
47.         // this is the main forward raycast
48.         if(Physics.Raycast(probePoint.position, transform.forward, out hit, probeRange)){
49.             if(obstacleInPath != target.transform) { // ignore our target
50.                 Debug.Log("Found an object in path! - " + gameObject.name);
51.                 Debug.DrawLine(transform.position, hit.point, Color.green);
52.                 previousCastMissed = false;
53.                 obstacleAvoid = true;
54.                 nma.Stop(true);
55.                 nma.ResetPath();
56.                 if(hit.transform != transform) {                 
57.                     obstacleInPath = hit.transform;
58.                     Debug.Log("I hit: " + hit.transform.gameObject.name);              
59.                     dir += hit.normal * turnSpeed;
60.                    
61.                     Debug.Log("moving around an object - " + gameObject.name);
62.                    
63.                 }
64.             }
65.         }
66.         // if we did see something before, but now the forward raycast is turned out of range, check the sides
67.         // without this, the character bumps into the object and sort of bounces (usually) until it gets
68.         // past.  This is a better approach :)
69.         if(obstacleAvoid  previousCastMissed  Physics.Raycast(leftR.position, transform.forward,out hit, probeRange)) {
70.             if(obstacleInPath != target.transform) { // ignore our target
71.                 Debug.DrawLine(leftR.position, hit.point, Color.red);
72.                 obstacleAvoid = true;
73.                 nma.Stop();
74.                 if(hit.transform != transform) {
75.                     obstacleInPath = hit.transform;
76.                     previousCastMissed = false;
77.                     //Debug.Log("moving around an object");
78.                     dir += hit.normal * turnSpeed;             
79.                 }
80.             }
81.         }
82.         // check the other side :)
83.         if(obstacleAvoid  previousCastMissed  Physics.Raycast(rightR.position, transform.forward,out hit, probeRange)) {
84.             if(obstacleInPath != target.transform) { // ignore our target
85.                 Debug.DrawLine(rightR.position, hit.point, Color.green);
86.                 obstacleAvoid = true;
87.                 nma.Stop();
88.                 if(hit.transform != transform) {
89.                     obstacleInPath = hit.transform;
90.                     dir += hit.normal * turnSpeed;
91.                 }
92.             }
93.         }
94.        
95.         // turn Nav back on when obstacle is behind the character!!
96.          if (obstacleInPath != null) {
97.             Vector3 forward = transform.TransformDirection(Vector3.forward);
98.             Vector3 toOther = obstacleInPath.position - transform.position;
99.             if (Vector3.Dot(forward, toOther) < 0) {
100.                 //print("The other transform is behind me!");
101.                 Debug.Log("Back on Navigation! unit - " + gameObject.name);
102.                 obstacleAvoid = false; // don't let Unity nav and our avoidance nav fight, character does odd things
103.                 obstacleInPath = null; // Hakuna Matata
104.                 nma.ResetPath();
105.                 nma.SetDestination(target.position);
106.                 nma.Resume(); // Unity nav can resume movement control
107.             }
108.            
109.         }
110. //     
111.         // this is what actually moves the character when under avoidance control
112.         if(obstacleAvoid) {
113.             Quaternion rot = Quaternion.LookRotation(dir);
114.             transform.rotation = Quaternion.Slerp(transform.rotation, rot, Time.deltaTime);
115.             transform.position += transform.forward * nma.speed * Time.deltaTime;
116.         }      
117.     }
118.    
119.     public void SetTarget(Transform tIn) {
120.         target = tIn;  
121.     }    
122. }
123.  

Cheers,

Galen

 

This sounds great, thanks for sharing!

 

Thanks, A lot, I know It's been 8 years still... you saved me from a great deal of frustration + time.

 

i got error in this line
if (obstacleAvoid previousCastMissed Physics.Raycast(leftR.position, transform.forward, out hit, probeRange)) {

 

place && between like:
obstacleAvoid && previousCastMissed && Physics.Raycast