Generating a random position on Navmesh.

I am making a open-world game where i'll have NPCs wandering around the city. I wonder if there is any way to generate a random position that never is off the Navmesh. Thanks for your help.

 

Hi,

NavMesh.RayCast, NavMesh.SamplePosition and NavMesh.CalculatePath may help

 

Thanks. Do you have any ideas on how to implement this?

 

I'm putting waypoint on a map, then I select random waypoint to follow.
Pre-made waypoint doesn't mean they cannot be created thought script or any other tools.

 

Thanks very much, once again, but i need ideas on what code to use. Would that be okay?

 

Hi, here some pseudocode how to select new waypoint

Code (CSharp):

1. private GameObject[] viewpoints;
2. waypoints = GameObject.FindGameObjectsWithTag("Sidewalk Objective");          
3. .....
4. if (waypoint)
5. {
6.   var v2tmp = transform.position - waypoint.transform.position;
7.   if (v2tmp.sqrMagnitude < TargetTolerance)
8.   {
9.     waypoint = null;
10.   }
11. }
12. if (!waypoint)
13. {
14.   var len = viewpoints.Length-1;
15.   var pos = UnityEngine.Random.Range(0, len);
16.   waypoint = viewpoints[pos];
17.   Agent.SetDestination(waypoint.transform.position);
18. }

 

I dunno if it'll help you or not, but in my game I select random locations on my NavMesh and spawn a bunch of people and they walk around to random destinations, when reaching those destinations they choose another random one and keep doing that. It's not perfectly random but it's pretty decent, IMO.

Here's some relevant code I have. The ObjectRandomizer is just a free Unity asset that allows you to put a bunch of objects in a list and easily grab random ones.

Code (CSharp):

1.  
2. private List<GameObject> spawnedPeople;
3. public int TotalNumberOfPeopleToSpawn;
4.  
5. void Start()
6.     {
7.         spawnedPeople = new List<GameObject>();
8.  
9.         SpawnAllPeople();
10.     }
11.  
12. private void SpawnAllPeople()
13.     {
14.         ObjectRandomizer objectRandomizer = GetComponent<ObjectRandomizer>();
15.  
16.         // spawn all people
17.         for (int personIndex = 0; personIndex < TotalNumberOfPeopleToSpawn; personIndex += 1)
18.         {
19.             // get a game location on the board
20.             Vector3 randomBoardLocation = GetRandomGameBoardLocation();
21.  
22.             // spawn a random person prefab at that location
23.             GameObject spawnedPerson = SpawnPersonAtLocation(randomBoardLocation, objectRandomizer);
24.  
25.             //Debug.Log("Spawned " + spawnedPerson.name + " at " + randomBoardLocation);
26.          
27.             // add the spawned person to our collection
28.             spawnedPeople.Add(spawnedPerson);
29.         }
30.     }
31.  
32.     /// <summary>
33.     /// Spawns a random person at the given spawn point.
34.     /// </summary>
35.     /// <param name="spawnPosition">The position to spawn the person at.</param>
36.     /// <param name="objectRandomizer">ObjectRandomizer that spawns people.</param>
37.     /// <returns>The newly spawned person.</returns>
38.     private GameObject SpawnPersonAtLocation(Vector3 spawnPosition, ObjectRandomizer objectRandomizer)
39.     {
40.         // get a random person prefab to spawn
41.         GameObject randomPersonPrefab = (GameObject)objectRandomizer.RandomObject();
42.  
43.         // spawn the person at the current spawn point
44.         GameObject personGameObject = Instantiate(randomPersonPrefab, spawnPosition, Quaternion.identity);
45.  
46.         Vector3 randomDestination = GetRandomGameBoardLocation();
47.         Person person = personGameObject.GetComponent<Person>();
48.         person.CurrentDestination = randomDestination;
49.  
50.         Debug.Log("Assigned CurrentDestination to " + person.name);
51.  
52.         //Debug.Log("Random dest: " + randomDestination);
53.      
54.         personGameObject.name = person.name + "_" + spawnPosition.x + "_" + spawnPosition.y + "_" + spawnPosition.z;
55.         return personGameObject;
56.     }
57.  
58.     /// <summary>
59.     /// Selects a random point on the game board (NavMesh).
60.     /// </summary>
61.     /// <returns>Vector3 of the random location.</returns>
62.     private Vector3 GetRandomGameBoardLocation()
63.     {
64.         NavMeshTriangulation navMeshData = NavMesh.CalculateTriangulation();
65.  
66.         int maxIndices = navMeshData.indices.Length - 3;
67.  
68.         // pick the first indice of a random triangle in the nav mesh
69.         int firstVertexSelected = UnityEngine.Random.Range(0, maxIndices);
70.         int secondVertexSelected = UnityEngine.Random.Range(0, maxIndices);
71.  
72.         // spawn on verticies
73.         Vector3 point = navMeshData.vertices[navMeshData.indices[firstVertexSelected]];
74.  
75.         Vector3 firstVertexPosition = navMeshData.vertices[navMeshData.indices[firstVertexSelected]];
76.         Vector3 secondVertexPosition = navMeshData.vertices[navMeshData.indices[secondVertexSelected]];
77.  
78.         // eliminate points that share a similar X or Z position to stop spawining in square grid line formations
79.         if ((int)firstVertexPosition.x == (int)secondVertexPosition.x || (int)firstVertexPosition.z == (int)secondVertexPosition.z)
80.         {
81.             point = GetRandomGameBoardLocation(); // re-roll a position - I'm not happy with this recursion it could be better
82.         }
83.         else
84.         {
85.             // select a random point on it
86.             point = Vector3.Lerp(firstVertexPosition, secondVertexPosition, UnityEngine.Random.Range(0.05f, 0.95f));
87.         }
88.  
89.         return point;
90.     }

 

Thanks

 

Thank you very much, that's exactly what I was looking for!

 

Weighting each triangle by their area should more evenly spread the points, but otherwise It won't get much better than using the mesh triangulation data

 

I have a large rolling terrain - 5000 by 5000. I have trees with colliders on them and use a NavMesh. I have a deer having a NavMeshAgent that I would like to roam around this terrain to random locations. Since the terrain has various heights, I don't know how to program it to do this. I have included a method that first checks to see if there is a gameobject at a specific random location before I tell it to move there. I don't know if this will work. I know I need to put the movement into the update method using Time.Deltatime along with the running of the animation. I'm just wondering if this routine will work. I would appreciate any modifications you can suggest.
void MoveTo()
{
xPoint = Random.Range(-2600, 2300);
zPoint = Random.Range(-5700, 700);
targetPos = new Vector3(xPoint, 0, zPoint);
Collider[] intersecting = Physics.OverlapSphere(targetPos, 0.01f);
if (intersecting.Length == 0)
{
// can move to this destination
navMeshAgent.SetDestination(targetPos);
}
}