tools-unity-navmesh

Unity NavMesh Pathfinding

Overview

NavMesh provides AI pathfinding in Unity. This skill covers safe usage patterns to prevent the 30K+ pathfinding errors seen in production.

When to Use

• AI movement and navigation
• Enemy patrolling and chasing
• NPC pathfinding
• Dynamic obstacle avoidance
• Multi-agent navigation

Critical Safety Patterns

Graph Validation Before Query

using Pathfinding;

public class SafePathfinder
{
    private readonly Seeker _seeker;
    
    public bool TryCalculatePath(Vector3 start, Vector3 end, out Path path)
    {
        path = null;
        
        // CRITICAL: Check graph exists
        if (AstarPath.active == null)
        {
            Debug.LogError("No AstarPath instance active");
            return false;
        }
        
        if (AstarPath.active.graphs == null || AstarPath.active.graphs.Length == 0)
        {
            Debug.LogError("No graphs available");
            return false;
        }
        
        // Check if position is on navmesh
        var startNode = AstarPath.active.GetNearest(start).node;
        var endNode = AstarPath.active.GetNearest(end).node;
        
        if (startNode == null || !startNode.Walkable)
        {
            Debug.LogWarning($"Start position {start} not on walkable navmesh");
            return false;
        }
        
        if (endNode == null || !endNode.Walkable)
        {
            Debug.LogWarning($"End position {end} not on walkable navmesh");
            return false;
        }
        
        // Safe to calculate path
        _seeker.StartPath(start, end, OnPathComplete);
        return true;
    }
    
    private void OnPathComplete(Path p)
    {
        if (p.error)
        {
            Debug.LogWarning($"Path failed: {p.errorLog}");
            return;
        }
        
        // Use path
    }
}

Null Graph Guard (Critical Fix for 30K errors)

public class PathfindingGuard
{
    public static bool IsPathfindingReady()
    {
        // Check 1: AstarPath singleton exists
        if (AstarPath.active == null)
            return false;
        
        // Check 2: Data is loaded
        if (AstarPath.active.data == null)
            return false;
        
        // Check 3: Graphs exist
        if (AstarPath.active.data.graphs == null)
            return false;
        
        // Check 4: At least one graph is scanned
        foreach (var graph in AstarPath.active.data.graphs)
        {
            if (graph != null && graph.CountNodes() > 0)
                return true;
        }
        
        return false;
    }
}

// Usage in AI
public class EnemyAI : MonoBehaviour
{
    private void RequestPath()
    {
        if (!PathfindingGuard.IsPathfindingReady())
        {
            // Defer pathfinding or use fallback behavior
            StartCoroutine(WaitForPathfinding());
            return;
        }
        
        _seeker.StartPath(transform.position, _target.position);
    }
    
    private IEnumerator WaitForPathfinding()
    {
        while (!PathfindingGuard.IsPathfindingReady())
        {
            yield return new WaitForSeconds(0.5f);
        }
        
        RequestPath();
    }
}