godot-physics

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Physics Systems for Godot 4.x

Comprehensive patterns for physics, collisions, and movement in Godot 4.x.

Collision Layers and Masks (Godot 4.x Typed System)

Godot 4.x uses bit-based collision layer/mask system for efficient spatial queries.

Configuring Collision Layers

Set layers in the editor via Inspector > CollisionShape3D > Collision Layer (bits 1-32).

gdscript

# Recommended layer layout
const LAYER_PLAYER = 0x1
const LAYER_ENEMIES = 0x2
const LAYER_PROJECTILES = 0x4
const LAYER_ENVIRONMENT = 0x8
const LAYER_PICKUPS = 0x10
const LAYER_TRIGGERS = 0x20

collision_layer = LAYER_PLAYER
collision_mask = LAYER_ENVIRONMENT | LAYER_PICKUPS

Layer Design Best Practices

Layer	Bit	Use Case
1	`0x1`	Player characters
2	`0x2`	Enemies and NPCs
4	`0x4`	Projectiles and weapons
8	`0x8`	Environment / terrain
16	`0x10`	Pickups and collectibles
32	`0x20`	Triggers (Area-only)

Typed Collision Queries

gdscript

var ray_query := PhysicsRayQueryParameters3D.new()
ray_query.from = camera.global_position
ray_query.to = global_position + forward * range
ray_query.collision_mask = LAYER_ENVIRONMENT
ray_query.exclude = [self]

var result = get_world_3d().direct_space.intersect_ray(ray_query)
if result:
    var collider = result.get("collider")
    print("Hit: ", collider.get_name())

Rigid Body Dynamics

Basic Rigid Body Setup

gdscript

class_name PlayerRigidBody extends CharacterBody3D

@export var gravity_scale: float = 1.0
@export var jump_force: float = 8.0
@export var move_speed: float = 5.0

var velocity := Vector3.ZERO

func _physics_process(delta: float) -> void:
    velocity.y -= 9.8 * gravity_scale * delta
    var input_dir := Input.get_vector("move_left", "move_right", "move_up", "move_down")
    velocity.x = input_dir.x * move_speed
    velocity.z = input_dir.y * move_speed
    move_and_slide()
    if is_on_floor() and Input.is_action_just_pressed("jump"):
        velocity.y = jump_force

Physics Material

gdscript

var bouncy_material := PhysicsMaterial.new()
bouncy_material.bounce = 0.8
bouncy_material.friction = 0.2
collision_shape.shape.material = bouncy_material

Rigid Body with Forces

gdscript

class_name Projectile extends RigidBody3D

@export var lifetime: float = 3.0
@export var damage: int = 10

func _ready() -> void:
    linear_velocity = transform.basis.z * 20.0
    get_tree().create_timer(lifetime).timeout.connect(queue_free)

func _on_body_entered(body: Node3D) -> void:
    if body is Enemy:
        body.take_damage(damage)
        queue_free()

Character Controllers

CharacterBody3D Movement Pattern

gdscript

class_name ThirdPersonController extends CharacterBody3D

@export var walk_speed: float = 4.0
@export var run_speed: float = 8.0
@export var jump_velocity: float = 4.5
@export var gravity_amount: float = 9.8
@export var sprint_factor: float = 2.0

var _is_sprinting := false

func _physics_process(delta: float) -> void:
    if not is_on_floor():
        velocity.y -= gravity_amount * delta
    if is_on_floor() and Input.is_action_just_pressed("jump"):
        velocity.y = jump_velocity
    var input_dir := Vector2.ZERO
    input_dir = Vector2(
        Input.get_axis("move_left", "move_right"),
        Input.get_axis("move_up", "move_down")
    )
    _is_sprinting = Input.is_action_pressed("sprint")
    var direction := (transform.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()
    if direction:
        var spd = run_speed * sprint_factor if _is_sprinting else walk_speed
        velocity.x = direction.x * spd
        velocity.z = direction.z * spd
    else:
        velocity.x = move_toward(velocity.x, 0, walk_speed)
        velocity.z = move_toward(velocity.z, 0, walk_speed)
    move_and_slide()

CharacterBody2D Platformer Pattern

gdscript

class_name PlatformerCharacter extends CharacterBody2D

@export var speed: float = 200.0
@export var jump_force: float = -450.0
@export var gravity: float = 1200.0
@export var max_fall_speed: float = 700.0
@export var acceleration: float = 800.0
@export var friction: float = 600.0

func _physics_process(delta: float) -> void:
    if not is_on_floor():
        velocity.y += gravity * delta
        velocity.y = min(velocity.y, max_fall_speed)
    if is_on_floor() and Input.is_action_just_pressed("jump"):
        velocity.y = jump_force
    var move_input := Input.get_axis("move_left", "move_right")
    if move_input:
        velocity.x = move_toward(velocity.x, move_input * speed, acceleration * delta)
    else:
        velocity.x = move_toward(velocity.x, 0, friction * delta)
    move_and_slide()

Area Nodes for Triggers and Detection

Basic Pickup Zone

gdscript

class_name PickupZone extends Area3D

@export var pickup_scene: PackedScene
@export var min_items: int = 1
@export var max_items: int = 3
var _has_been_activated := false

func _ready() -> void:
    body_entered.connect(_on_body_entered)

func _on_body_entered(body: Node3D) -> void:
    if _has_been_activated: return
    if body is CharacterBody3D:
        _spawn_items()
        _has_been_activated = true
        queue_free()

func _spawn_items() -> void:
    var count = randi() % (max_items - min_items + 1) + min_items
    for i in range(count):
        var item = pickup_scene.instantiate()
        item.position = global_position + Vector3(randf() * 2 - 1, 0.5, randf() * 2 - 1)
        get_tree().root.add_child(item)

Enemy Detection Sensor

gdscript

class_name EnemySensor extends Area3D

signal player_detected(player: CharacterBody3D)
signal player_lost(player: CharacterBody3D)

@export var detection_radius: float = 10.0
@export var detection_layers: int = 0x1

func _ready() -> void:
    body_entered.connect(_on_body_entered)
    body_exited.connect(_on_body_exited)
    var sphere := SphereShape3D.new()
    sphere.radius = detection_radius
    $CollisionShape3D.shape = sphere
    collision_mask = detection_layers

func _on_body_entered(body: Node3D) -> void:
    if body is CharacterBody3D:
        player_detected.emit(body)

func _on_body_exited(body: Node3D) -> void:
    if body is CharacterBody3D:
        player_lost.emit(body)

Physics Interpolation (Godot 4.x Feature)

Godot 4.x supports physics interpolation for smooth rendering between physics ticks.

Enabling Physics Interpolation

Enable in Project Settings > Rendering > Other > Physics Interpolation set to "Interpolate". The engine automatically interpolates transforms between physics ticks when rendering. No extra code needed for standard nodes.

For custom rendering, use the built-in interpolation factor available through the rendering pipeline.

Performance: Bulk Physics Queries

Space State Batched Queries

gdscript

func get_all_collisions_in_area(origin: Vector3, radius: float, mask: int) -> Array:
    var query := PhysicsShapeQueryParameters3D.new()
    var sphere := SphereShape3D.new()
    sphere.radius = radius
    query.shape = sphere
    query.transform = Transform3D.IDENTITY.translated(origin)
    query.collision_mask = mask
    query.exclude = [self]
    var space = get_world_3d().direct_space
    return space.intersect_shape(query)

func aoe_attack(center: Vector3, radius: float, damage: int) -> void:
    var hits := get_all_collisions_in_area(center, radius, LAYER_ENEMIES | LAYER_PROJECTILES)
    for hit in hits:
        var collider = hit.get("collider")
        if collider is Enemy:
            collider.take_damage(damage)

Collision Layer Optimization

Only check layers you need — avoid collision_mask = 0xFFFFFFFF
Use NavigationServer3D for pathfinding queries
Use small-radius Area3D nodes for proximity checks
Avoid querying the entire world every frame

Godot 4.7 Physics Notes

Physics interpolation is more robust with improved accuracy
Use AreaLight3D for dynamic light casting on visible surfaces
Test physics performance with Perfetto tracing on mobile targets

Quick Reference: Movement Methods

Method	Use Case	Returns
`move_and_slide()`	Standard character movement	SlideFlags
`move_and_collide()`	When you need collision info	CollisionData or null
`move_and_snap()`	Platformer with snap-to-floor	SlideFlags
`move_teleport()`	Teleportation (no sliding)	CollisionData or null

MCP Bridge Tools (Optional — Live Editor Integration)

When the MCP bridge is running (Phase 2), these tools enhance physics debugging:

`physics_debug_draw` — Toggle collision shape visualization in editor
`physics_query_shape` — Run shape queries from any position without placing nodes
`rigid_body_apply_force` — Apply forces to rigid bodies for testing
`physics_stats` — View active physics bodies, sleep count, and frame cost

Note: MCP tools require the Godot editor to be running with the MCP plugin enabled. Skills work independently without the bridge.

Physics Systems for Godot 4.x

Collision Layers and Masks (Godot 4.x Typed System)

Configuring Collision Layers

Layer Design Best Practices

Typed Collision Queries

Rigid Body Dynamics

Basic Rigid Body Setup

Physics Material

Rigid Body with Forces

Character Controllers

CharacterBody3D Movement Pattern

CharacterBody2D Platformer Pattern

Area Nodes for Triggers and Detection

Basic Pickup Zone

Enemy Detection Sensor

Physics Interpolation (Godot 4.x Feature)

Enabling Physics Interpolation

Performance: Bulk Physics Queries

Space State Batched Queries

Collision Layer Optimization

Godot 4.7 Physics Notes

Quick Reference: Movement Methods

MCP Bridge Tools (Optional — Live Editor Integration)

References

関連する Skills

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