compsci_godot_albert/_subsections/sec03/lesson-30.org

Section 03 - Lesson 30 | Section Review

• Links
• Notes
  • paddle scene
    • node composition
    • script view: paddle.gd
      • use @export to create speed variable
      • override _process function
  • gem scene
    • node composition
    • script view: gem.gd
      • set class name
      • set a signal property
      • set export property
    • modify _process
      • determine if the gem has gone out of bounds
      • if gem went out of bounds
        • emit signal
        • stop the gem and remove it from the node tree
  • Game scene
    • preload assets
    • add a PackedScene variable
    • use onready to add nodes in tree scene
    • spawn gem at _ready
    • stop all function
    • turn off audio
    • whenever timer times out spawn a gem
    • when the paddle gets hit by a gem

Links

• TOC - Godot Notes
• S03:L42.30 - Section Review

Notes

paddle scene

node composition

• root: Area2D
• Sprite2D
• CollisionShape2D

script view: paddle.gd

• extends Area2D

use @export to create speed variable

• can be modified in Inspector
• give default value

override _process function

• check if Input.is_action_pressed

  • is 'left'
  • is 'right'

• move paddle

  • get the Node2D.position property

    • multiply speed by delta and add or subtract it from position.x
    • delta is number of seconds that elapsed since the previous frame

gem scene

node composition

• root: Area2D
• Sprite2D
• CollisionShape2D

script view: gem.gd

• extends Area2D

set class name

• class_name Gem
• this allows us to instantiate Gem objects in scripts

set a signal property

• signal on_gem_off_screen
• allows us to attach listeners who will be notified when we emit a signal

set export property

• @export var speed
• lets us set the speed in the Inspector

modify _process

determine if the gem has gone out of bounds

• this is going to be the edge of the viewport

• check position property against the viewport rect property

  if position.y > get_viewport_rect().size.y

if gem went out of bounds

emit signal

on_gem_off_screen.emit()

stop the gem and remove it from the node tree

• stop going through the process function
• delete node at the end of the current frame

set_process(false)
queue_free()

Game scene

preload assets

• using const to set builtin preload function

   const EXPLOSDE = preload("res://assets/explode.wav")

add a PackedScene variable

• allows us to instantiate gem scenes

• export allows us to drag and drop the scene we want into the inspector

  @export var gem_scene: PackedScene
  
   # when time comes to use it
   gem_scene.instantiate()
   add_child(gem_scene)

• otherwise we would have to preload it

   gem_scene = preload("res://somescene.tscn").instantiate()
   add_child(gem_scene)

use onready to add nodes in tree scene

@onready var label: Label = $Label
@onready var timer: Timer = $Timer
@onready var audio_stream_player_2d: AudioStreamPlayer2D = $AudioStreamPlayer2D

• these are all scenes in the Game tree
• use onready to attach them to variables for use in game script
• onready makes sure it's available so we dont end up with a null reference

spawn gem at _ready

• in the ready function immediately call spawn_gem
• spawn Gem instantiates a gem scene and type casts it to a Gem class
• connect any signals
• set it's position

• add it as a child

  var new_gem: Gem = gem_scene.instantiate()
  new_gem.on_gem_off_screen.connect(game_over)
  new_gem.position = Vector2(xpos, ypos)
  add_child(new_gem)

stop all function

• stop the timer

• run through all children and set process to false

  timer.stop()
  for child in get_children():
   child.set_process(false)

turn off audio

• get references to audio and call 'stop' function
• you can also set another sound for ending and play that

 audio_stream_player_2d.stop()
 audio_stream_player_2d.stream = EXPLODE
 audio_stream_player_2d.play()

whenever timer times out spawn a gem

• we attached the timer to a signal to call a function that calls spawn gem

when the paddle gets hit by a gem

• increase score
• set the position of where the paddle got hit to the audio and play a sound
• free up the hit object (the gem)

func _on_padd_area_entered(area: Area2D) -> void:
	_score += 1
	label.text = "%05d" % _score
	audio_stream_player_2d.position = area.position
	audio_stream_player_2d.play()
	area.queue_free()