godot-navigation-pathfinding

What this skill does

# Navigation & Pathfinding

NavigationServer-powered pathfinding with avoidance and dynamic obstacles define robust AI movement.

## Available Scripts

### [dynamic_nav_manager.gd](scripts/dynamic_nav_manager.gd)
Expert runtime navigation mesh updates for moving platforms.

### [server_navigation_setup.gd](scripts/server_navigation_setup.gd)
Low-level `NavigationServer3D` usage (bypassing nodes). Creates maps, regions, and registers navmeshes entirely via RID for maximum performance.

### [async_dynamic_baking.gd](scripts/async_dynamic_baking.gd)
Expert logic for `bake_from_source_geometry_data_async`. Parses geometry on main thread then bakes in background to prevent procedural-gen stutters.

### [memory_optimized_queries.gd](scripts/memory_optimized_queries.gd)
Pattern for reusing `NavigationPathQueryParameters3D` and `NavigationPathQueryResult3D` objects to prevent frame-by-frame GC allocations.

### [terrain_cost_manager.gd](scripts/terrain_cost_manager.gd)
Controlling pathfinding logic using `region_set_enter_cost` and `region_set_travel_cost` to define high-penalty areas (mud, fire, water).

### [low_level_avoidance.gd](scripts/low_level_avoidance.gd)
Direct RVO (Reciprocal Velocity Obstacles) registration using server-side agents. Uses `NavigationServer3D.agent_set_avoidance_callback` for high-performance avoidance.

### [moving_obstacle_server.gd](scripts/moving_obstacle_server.gd)
Dynamic obstacle registration (e.g. for projectiles or rolling hazards) that push RVO agents away without full navmesh baking.

### [nav_link_traversal.gd](scripts/nav_link_traversal.gd)
Advanced handling of `NavigationLink3D` for jumps, teleports, and elevators. Detects link traversal and overrides standard movement.

### [layer_mask_navigation.gd](scripts/layer_mask_navigation.gd)
Architecture for multi-type navigation (e.g. Flying vs Walking vs Swimming) using 32-bit navigation layers and bitmasks.

### [agent_stuck_detection.gd](scripts/agent_stuck_detection.gd)
Robust AI recovery logic. Detects distance-over-time stalls and triggers jitter recovery or path recalculation.

### [group_avoidance_formations.gd](scripts/group_avoidance_formations.gd)
Coordinating crowd behavior. Strategies for avoiding individual agent clumping by using leader-relative target offsets.

## NEVER Do in Navigation & Pathfinding

- **NEVER set `target_position` before awaiting physics frame** — NavigationServer not ready in `_ready()`? Path fails silently. MUST `call_deferred()` then `await get_tree().physics_frame`.
- **NEVER use `NavigationRegion2D.bake_navigation_polygon()` at runtime** — Synchronous baking freezes game for 100+ ms. Use `NavigationServer.bake_from_source_geometry_data_async()` for stutter-free updates.
- **NEVER forget to check `is_navigation_finished()`** — Calling `get_next_path_position()` after reaching target = stale path, AI walks to old position.
- **NEVER use `avoidance_enabled` without setting radius** — Default radius = 0, agent passes through others. Set `nav_agent.radius = collision_shape.radius` for proper avoidance.
- **NEVER poll `target_position` every frame for chase AI** — Setting target 60x/sec = path recalculation spam. Use timer (0.2s intervals) or distance threshold for updates.
- **NEVER assume path exists** — Target unreachable (blocked by walls)? `get_next_path_position()` returns invalid. Check `is_target_reachable()` or validate path length.
- **NEVER use heavy node-based navigation for thousands of simple entities** — Use `NavigationServer3D/2D` RIDs directly to bypass node overhead.
- **NEVER call `get_path()` every frame** — Use `query_path()` with reused `NavigationPathQueryResult` objects to prevent massive heap allocation and GC pressure.
- **NEVER leave 'enter_cost' at 0 for high-penalty areas** — Use costs to make AI prefer logical paths (roads over water) instead of just shortest geometric distance.
- **NEVER ignore `agent_set_avoidance_callback`** — Always use the callback for safe velocity computation to avoid synchronization issues and "jittery" movement.

---

### 2D Navigation

```gdscript
# Scene structure:
# Node2D (Level)
#   ├─ NavigationRegion2D
#   │    └─ Polygon2D (draw walkable area)
#   └─ CharacterBody2D (Enemy)
#        └─ NavigationAgent2D
```

**Setup NavigationRegion2D:**
1. Add `NavigationRegion2D` node
2. Create **New NavigationPolygon**
3. Click "Edit" → Draw walkable area
4. Bake navigation mesh

### Basic AI Movement

```gdscript
extends CharacterBody2D

@onready var nav_agent := $NavigationAgent2D
@export var speed := 200.0

var target_position: Vector2

func _ready() -> void:
    # Wait for navigation to be ready
    call_deferred("setup_navigation")

func setup_navigation() -> void:
    await get_tree().physics_frame
    nav_agent.target_position = target_position

func _physics_process(delta: float) -> void:
    if nav_agent.is_navigation_finished():
        return
    
    var next_position := nav_agent.get_next_path_position()
    var direction := (next_position - global_position).normalized()
    
    velocity = direction * speed
    move_and_slide()

func set_target(pos: Vector2) -> void:
    target_position = pos
    nav_agent.target_position = pos
```

## NavigationAgent Properties

```gdscript
# Path recalculation
nav_agent.path_desired_distance = 10.0
nav_agent.target_desired_distance = 10.0

# Avoidance
nav_agent.radius = 20.0
nav_agent.avoidance_enabled = true

# Performance
nav_agent.path_max_distance = 500.0
```

## Advanced Patterns

### Chase Player

```gdscript
extends CharacterBody2D

@onready var nav_agent := $NavigationAgent2D
@export var speed := 150.0
@export var chase_range := 300.0

var player: Node2D

func _physics_process(delta: float) -> void:
    if not player:
        return
    
    var distance := global_position.distance_to(player.global_position)
    
    if distance <= chase_range:
        nav_agent.target_position = player.global_position
        
        if not nav_agent.is_navigation_finished():
            var next_pos := nav_agent.get_next_path_position()
            var direction := (next_pos - global_position).normalized()
            velocity = direction * speed
            move_and_slide()
```

### Patrol Points

```gdscript
extends CharacterBody2D

@onready var nav_agent := $NavigationAgent2D
@export var patrol_points: Array[Vector2] = []
@export var speed := 100.0

var current_point_index := 0

func _ready() -> void:
    if patrol_points.size() > 0:
        nav_agent.target_position = patrol_points[0]

func _physics_process(delta: float) -> void:
    if nav_agent.is_navigation_finished():
        _go_to_next_patrol_point()
        return
    
    var next_pos := nav_agent.get_next_path_position()
    var direction := (next_pos - global_position).normalized()
    velocity = direction * speed
    move_and_slide()

func _go_to_next_patrol_point() -> void:
    current_point_index = (current_point_index + 1) % patrol_points.size()
    nav_agent.target_position = patrol_points[current_point_index]
```

## 3D Navigation

```gdscript
extends CharacterBody3D

@onready var nav_agent := $NavigationAgent3D
@export var speed := 5.0

func _physics_process(delta: float) -> void:
    if nav_agent.is_navigation_finished():
        return
    
    var next_position := nav_agent.get_next_path_position()
    var direction := (next_position - global_position).normalized()
    
    velocity = direction * speed
    move_and_slide()
```

## Dynamic Obstacles

```gdscript
# Add NavigationObstacle2D to moving objects
# Scene:
# CharacterBody2D (MovingPlatform)
#   └─ NavigationObstacle2D

# Navigation automatically updates around it
```

## Signals

```gdscript
func _ready() -> void:
    nav_agent.velocity_computed.connect(_on_velocity_computed)
    nav_agent.navigation_finished.connect(_on_navigation_finished)

func _on_velocity_computed(safe_velocity: Vector2) -> void:
    velocity = safe_velocity
    move_and_slide()

func _on_navigation_finished() -> void:
    print("Reached des