Scenes inside node

Create the laser scene

So far, we created scenes in the editor

But this isn't always possible in a game! For example, the lasers are also a scene but one that is dynamically generated

We need to create a scene
We need to create an instance of the scene
We need to add the scene to the node tree

Only use the simpliest node possible In case of the laser, we will use Area2D

For 2. & 3. we need to preload the scene and use add_child() method

extends Node2D

var laser_scene: PackedScene = preload("res://scenes/projectiles/laser.tscn")

func _on_player_shoot_lazer():
	var laser = laser_scene.instantiate()
	# 1. update the laser position
	# 2. we have to move the laser
	# 3. I want to add the laser instance to a Node2D
    add_child(laser)

So now how we are supposed to update the laser position ?

Laser position

We can determine a random position for the laser, so add 3 marker2D on the gun and use them to determine the position of the laser

Laser position


	if Input.is_action_pressed("primary action") and can_laser:
		var laser_markers = $LaserStartPositions.get_children()
		var selected_laser = laser_markers[randi() % laser_markers.size()]
		# emit the position we selected
		shoot_lazer.emit(selected_laser.global_position)

How to have a random number ?

var random_number = numbers[randi() % numbers.size()]

We have use global_position because the laser is a child of the gun, so the position is relative to the gun Before we use only position so far is a local position: They are relative to the parent.

Global positions are an exact pixel coordinate that is independent from any parent

Imagine you are in your house: You have some relative position to the center of the house (your local position) but you still have a specific GPS location (global position)

You can add a Node2D with an offset of x:100 and y:200 and give it a child on the same position. The child will have a local position of x:0 and y:0 but a global position of x:100 and y:200

Laser movement

Simple, just add a script and add a process that move the laser

extends Area2D

@export var speed: int = 1000
var direction: Vector2 = Vector2.UP

func _process(delta):
	position += direction * speed * delta

To expose a class variable into the inspector, you need to add the export keyword

@export var speed = 100

Laser cleaner visibility

When you launch the game and select the remote vue you can see on each action, a new Laser node is added to the scene tree. It's not a problem for the game but it's not clean. To correct that, we added a Node2D projectiles inside the scene and we add the laser inside this node.


func _on_player_shoot_lazer(pos):
	var laser = laser_scene.instantiate()
	laser.position = pos
	# 3. I want to add the laser instance to a Node2D
	$Projectiles.add_child(laser)