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Using NavigationAgents

NavigationsAgents are helper nodes to facilitate common calls to the NavigationServer API on behalf of the parent actor node in a more convenient manner for beginners.

2D and 3D version of NavigationAgents are available as NavigationAgent2D and NavigationAgent3D respectively.

NavigationsAgents are entirely optional for navigation pathfinding. The functionality of NavigationsAgents can be recreated with scripts and direct calls to the NavigationServer API. If the default NavigationsAgent does not do what you want for your game feel free to design your own NavigationsAgent with scripts.

Warning

NavigationsAgent nodes and NavigationServer agents are not the same. The later is an RVO avoidance agent and solely used for avoidance. RVO avoidance agents are not involved in regular pathfinding.

NavigationAgent Pathfinding

To use NavigationAgents for pathfinding, place a NavigationAgent2D/3D Node below a Node2D/3D inheriting parent node.

To have the agent query a path to a target position use the set_target_position() method. Once the target has been set, the next position to follow in the path can be retrieved with the get_next_path_position() function. Move the parent actor node to this position with your own movement code. On the next physics_frame, call get_next_path_position() again for the next position and repeat this until the path ends.

NavigationAgents have their own internal logic to proceed with the current path and call for updates. NavigationAgents recognize by distance when a path point or the final target is reached. NavigationAgents refresh a path automatically when too far away from the current pathpoint. The important updates are all triggered with the get_next_path_position() function when called in _physics_process().

Be careful calling other NavigationAgent functions not required for path movement while the actor is following a path, as many function trigger a full path refresh.

Note

New NavigationAgents will automatically join the default navigation map for their 2D/3D dimension.

Warning

Resetting the path every frame (by accident) might get the actor to stutter or spin around in place.

NavigationAgents were designed with _physics_process() in mind to keep in sync with both NavigationServer3D and PhysicsServer3D.

They work well out of the box with CharacterBody2D and CharacterBody3D as well as any rigid bodies.

Warning

The important restriction for non-physics characters is that the NavigationAgent node only accepts a single update each physics_frame as further updates will be blocked.

Warning

If a NavigationAgent is used with _process() at high framerate make sure to accumulate the values of multiple frames and call the NavigationAgent function only once each physics_frame.

NavigationAgent Avoidance

This section explains how to use the built-in avoidance specific to NavigationAgent nodes. For general avoidance use and more technical details on RVO avoidance see Using Agent Avoidance.

In order for NavigationAgents to use the avoidance feature the enable_avoidance property must be set to true.

../../_images/agent_avoidance_enabled.png

Note

Only other agents on the same map that are registered for avoidance themself will be considered in the avoidance calculation.

The following NavigationAgent properties are relevant for avoidance:

  • The property radius controls the size of the avoidance circle around the agent. This area describes the agents body and not the avoidance maneuver distance.

  • The property neighbor_distance controls the search radius of the agent when searching for other agents that should be avoided. A lower value reduces processing cost.

  • The property max_neighbors controls how many other agents are considered in the avoidance calculation if they all have overlapping radius. A lower value reduces processing cost but a too low value may result in agents ignoring the avoidance.

  • The property time_horizion controls the avoidance maneuver start and end distance. How early and for how long an agents reacts to other agents within the neighbor_distance radius to correct its own velocity. A lower value results in avoidance kicking in with a very intense velocity change at a short distance while a high value results in very early but small velocity changes.

  • The property max_speed controls the maximum velocity assumed for the agents avoidance calculation. If the agents parents moves faster than this value the avoidance safe_velocity might not be accurate enough to avoid collision.

The velocity_computed signal of the agent node must be connected to receive the safe_velocity calculation result.

../../_images/agent_safevelocity_signal.png

Additional the current velocity of the agents parent must be set for the agent in _physics_process() with set_velocity().

After a short wait for processing the avoidance (still in the same frame) the safe_velocity vector will be received with the signal. This velocity vector should be used to move the NavigationAgent’s parent node in order to avoidance collision with other avoidance registered agents in proximity.

RVO exists in its own space and has no information from navigation meshes or physics collision. Behind the scene avoidance agents are just circles with different radius on a flat plane. In narrow places obstructed with collision objects, the avoidance maneuver radius needs to be reduced considerably or disabled else the avoidance velocity will get actors stuck on collision easily.

Note

Avoidance should be seen as a last resort option for constantly moving objects that cannot be re(baked) to a navigationmesh efficiently in order to move around them.

Warning

Actors that move according to their avoidance agent velocity will not move at full speed, can leave the navigation mesh bounds and can make movement pauses when the avoidance simulation becomes unsolvable.

Using the NavigationAgent enable_avoidance property is the preferred option to toggle avoidance but the following scripts for NavigationAgents can be used to create or delete avoidance callbacks for the agent RID.

GDScript

  1. extends NavigationAgent2D
  3. var agent: RID = get_rid()
  4. # Create avoidance callback
  5. NavigationServer2D.agent_set_callback(agent, Callable(self, "_avoidance_done"))
  7. # Delete avoidance callback
  8. NavigationServer2D.agent_set_callback(agent, Callable())

GDScript

  1. extends NavigationAgent3D
  3. var agent: RID = get_rid()
  4. # Create avoidance callback
  5. NavigationServer3D.agent_set_callback(agent, Callable(self, "_avoidance_done"))
  7. # Delete avoidance callback
  8. NavigationServer3D.agent_set_callback(agent, Callable())

NavigationAgent Script Templates

The following sections provides script templates for nodes commonly used with NavigationAgents.

Actor as Node3D

This script adds basic navigation movement to a Node3D with a NavigationAgent3D child node.

GDScript

  1. extends Node3D
  3. @export var movement_speed: float = 4.0
  4. @onready var navigation_agent: NavigationAgent3D = get_node("NavigationAgent3D")
  5. var movement_delta: float
  7. func _ready() -> void:
  8.     navigation_agent.velocity_computed.connect(Callable(_on_velocity_computed))
  10. func set_movement_target(movement_target: Vector3):
  11.     navigation_agent.set_target_position(movement_target)
  13. func _physics_process(delta):
  14.     if navigation_agent.is_navigation_finished():
  15.         return
  17.     movement_delta = movement_speed * delta
  18.     var next_path_position: Vector3 = navigation_agent.get_next_path_position()
  19.     var current_agent_position: Vector3 = global_position
  20.     var new_velocity: Vector3 = (next_path_position - current_agent_position).normalized() * movement_delta
  21.     if navigation_agent.avoidance_enabled:
  22.         navigation_agent.set_velocity(new_velocity)
  23.     else:
  24.         _on_velocity_computed(new_velocity)
  26. func _on_velocity_computed(safe_velocity: Vector3) -> void:
  27.     global_position = global_position.move_toward(global_position + safe_velocity, movement_delta)

Actor as CharacterBody3D

This script adds basic navigation movement to a CharacterBody3D with a NavigationAgent3D child node.

GDScript

  1. extends CharacterBody3D
  3. @export var movement_speed: float = 4.0
  4. @onready var navigation_agent: NavigationAgent3D = get_node("NavigationAgent3D")
  6. func _ready() -> void:
  7.     navigation_agent.velocity_computed.connect(Callable(_on_velocity_computed))
  9. func set_movement_target(movement_target: Vector3):
  10.     navigation_agent.set_target_position(movement_target)
  12. func _physics_process(delta):
  13.     if navigation_agent.is_navigation_finished():
  14.         return
  16.     var next_path_position: Vector3 = navigation_agent.get_next_path_position()
  17.     var current_agent_position: Vector3 = global_position
  18.     var new_velocity: Vector3 = (next_path_position - current_agent_position).normalized() * movement_speed
  19.     if navigation_agent.avoidance_enabled:
  20.         navigation_agent.set_velocity(new_velocity)
  21.     else:
  22.         _on_velocity_computed(new_velocity)
  24. func _on_velocity_computed(safe_velocity: Vector3):
  25.     velocity = safe_velocity
  26.     move_and_slide()

Actor as RigidBody3D

This script adds basic navigation movement to a RigidBody3D with a NavigationAgent3D child node.

GDScript

  1. extends RigidBody3D
  3. @export var movement_speed: float = 4.0
  4. @onready var navigation_agent: NavigationAgent3D = get_node("NavigationAgent3D")
  6. func _ready() -> void:
  7.     navigation_agent.velocity_computed.connect(Callable(_on_velocity_computed))
  9. func set_movement_target(movement_target: Vector3):
  10.     navigation_agent.set_target_position(movement_target)
  12. func _physics_process(delta):
  13.     if navigation_agent.is_navigation_finished():
  14.         return
  16.     var next_path_position: Vector3 = navigation_agent.get_next_path_position()
  17.     var current_agent_position: Vector3 = global_position
  18.     var new_velocity: Vector3 = (next_path_position - current_agent_position).normalized() * movement_speed
  19.     if navigation_agent.avoidance_enabled:
  20.         navigation_agent.set_velocity(new_velocity)
  21.     else:
  22.         _on_velocity_computed(new_velocity)
  24. func _on_velocity_computed(safe_velocity: Vector3):
  25.     linear_velocity = safe_velocity