12. Navigation: NavMesh

• This section covers enemy navigation: NavMesh, NavMesh Agent, NavMesh Obstacle.

Navigation mesh

• To define surfaces on which an agent can move, create a plane covering the entire floor in the base, and enable the Navigation Static property in the Window > AI > Navigation > Object tab (with that GameObject selected).
• To define objects that agents can't go through, select all of them and in the Navigation window > Object tab enable the Navigation Static property and set Navigation Area to "Not Walkable" (so the surfaces on top of those objects are not defined as walkable areas).
• In the Navigation window > Bake tab, click on the Bake button. The navigation mesh should now be ready.

NavMesh Agent

• Add the "Nav Mesh Agent" component to the GameObject that will represent the enemy. Remove the RigidBody component from the enemy GameObject if there is one.
• Create a new C# script "EnemyNavigation" (below), and set its public variable "Move Position Transform" to the player GameObject, so the enemy follows the player.
• In the enemy GameObject's Nav Mesh Agent component, set the Base Offset so the enemy is on the floor.

using UnityEngine;
using UnityEngine.AI;

public class EnemyNavigation : MonoBehaviour
{
    public Transform movePositionTransform;

    private NavMeshAgent navMeshAgent;

    void Awake()
    {
        navMeshAgent = GetComponent<NavMeshAgent>();
    }

    void Update()
    {
        navMeshAgent.destination = movePositionTransform.position;
    }
}

NavMesh Obstacle

• To allow the agent to go through doors when they are open, use the NavMesh Obstacle component.
• Add the NavMesh Obstacle component to doors that can open.
  • By default, they are treated as a rigidbody, so the enemy will collide with the doors.
  • In the obstacle component, enable the "Carve" property (so the NavMesh updates when the doors change position, so the enemy doesn't try to collide with the closed doors).
• In the Navigation window > Object tab (with the door selected) disable the Navigation Static property (if it was enabled).
• In the Navigation window > Bake tab, Clear and then Bake the NavMesh again.
• You can add the obstacle component to barrels and broken wall pieces as well.
• You can disable the renderer and collider components in the plane GameObject you created for NavMesh (note: you can't bake the NavMesh while the plane's renderer is disabled).

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