NavMeshPathGizmo.cs

// Draws the agent's path as Gizmo.
using UnityEngine;
using UnityEngine.AI;

namespace uMMORPG
{
    [RequireComponent(typeof(NavMeshAgent))]
    public class NavMeshPathGizmo : MonoBehaviour
    {
        void OnDrawGizmos()
        {
            // can't cache agent because reloading script sometimes clears cached
            NavMeshAgent agent = GetComponent<NavMeshAgent>();

            // get path
            NavMeshPath path = agent.path;

            // color depends on status
            Color color = Color.white;
            switch (path.status)
            {
                case NavMeshPathStatus.PathComplete: color = Color.white; break;
                case NavMeshPathStatus.PathInvalid: color = Color.red; break;
                case NavMeshPathStatus.PathPartial: color = Color.yellow; break;
            }

            // draw the path
            for (int i = 1; i < path.corners.Length; ++i)
                Debug.DrawLine(path.corners[i-1], path.corners[i], color);

            // draw velocity
            Debug.DrawLine(transform.position, transform.position + agent.velocity, Color.blue, 0, false);
        }
    }
}