compsci-godot-arpg/ch01/lesson-11.org

Lesson 11: Creating the first enemy

• Links
• Notes
  • Create a New Sprite
    • add the nodes
    • add animations node
    • add sprite sheet
    • Reposition the Sprite
    • add to world map
  • make the sprite movable
    • func _ready
    • func changeDirection
    • func updateVelocity
    • full script
  • update the sprite-moving-script.gd
    • at beginning of script add: @onready var animations = $AnimatedSprite2D
    • func updateAnimation
  • set end position to world scene marker
    • add marker 2D node to sprite
    • add Marker2D to the sprite script
    • assign Marker2D to endpoint
    • in func _ready
• Video Contents

Links

• TOC - Godot Notes

Notes

Create a New Sprite

add the nodes

1. Make a new scene
2. Add a CharacterBody2D node
3. to the new characterbody node, add a AnimatedSprite2D node

add animations node

1. add the sprite sheet to the project ./art

2. go to AnimatedSprite2D node-> Animated Sprite2D -> Animation-> Sprite Frames

   1. click where it says empty, and select New Sprite Frames
   2. now click inside "New sprite Frames", this will open up the SpriteFrames editor at the bottom
   3. The options will be Animations and Animations Frames

add sprite sheet

1. click on 'default' in the animations section on the left side of the SpriteFrames editor

   
2. change name of the animation from 'default' to a name describing the animation

3. now click on the 'add frames from sprite sheet icon' in the Animations Frame panel of the Sprite Frame Editor

   
   • select the sprites you want to add and hit the Add button

   • elements of the add frames

     • horizontal and vertical determines rows and columns in spritesheet
     • size determines pixel sizes

4. click on the 'new animation' button to add another animation and repeat the process above

   

Reposition the Sprite

• this is important for y-sorting
• in the scene, select and move the sprite above the x-axis

see how the animation looks by going to AnimatedSprite2D-> Animation choose from the dropdown in Animation to pick which animation you want incrase or decrease the Frame number for the correct frame

add to world map

• save as whatever name you want
• switch to world scene
• add the sprite into the same layer area as the player

make the sprite movable

• add a new script on the root node of the sprite

  • erase everything in script except for extends CharacterBody2D at the top

func _ready

• Vector2(0, 3*16)

  • 16 is the height of the sprite
  • 3 is how many sprites spaces we move
• startPosition: where the sprite starts at
• endPosition: about 3 sprite lengths up

func changeDirection

• switch end and start positions
• this way it will regard as what was the end as the new start

func updateVelocity

• moveDirection: we compare where we have to go 'endPosition' to where we CURRENTLY ARE 'position'

  • compare current position to goal position
  • get difference
  • use the normalization of the difference to find the direction moveDirection.normalized
  • use the length of the difference to find if we hit the limit of how far we need to go moveDirection.length < limit
• moveDirection.length < limit: if so, change the direction as above

• velocity = moveDirection.normalized * speed:

  • normalize the moveDirection so we get the direction alone
  • multiple it by how far the sprite is expected to move at any given time

full script

extends CharacterBody2D

@export var speed = 20
@export var limit = 0.5

var startPosition
var endPosition

func _ready():
	startPosition = position
	endPosition = startPosition + Vector2(0, 3*16)

func changeDirection():
	var tempEnd = endPosition
	endPosition = startPosition
	startPosition = tempEnd

func updateVelocity():
	var moveDirection = (endPosition - position)

	if moveDirection.length() < limit:
		changeDirection()

	velocity = moveDirection.normalized() * speed

func _physics_process(delta: float) -> void:
	updateVelocity()
	move_and_slide()

update the sprite-moving-script.gd

at beginning of script add: @onready var animations = $AnimatedSprite2D

1. @onready

   • The @onready keyword tells Godot to initialize the variable after the node is added to the scene tree. Normally, if you try to access nodes in the scene tree during the script's initialization (before they're fully ready), you might get errors because those nodes don't exist yet.
   • With @onready, the variable animations will be initialized once the node and its children have been added to the scene tree, ensuring it's ready to be used when the scene starts running.

2. var animations

   • creates a variable named 'animations'

3. $AnimatedSprite2D

   • The $ symbol is a shortcut in Godot's GDScript to quickly reference child nodes in the scene tree. In this case, $AnimatedSprite2D accesses the AnimatedSprite2D node that is a child of the current node the script is attached to.
   • AnimatedSprite2D refers to the specific node in your scene that handles sprite animations. It has functionalities such as starting, stopping, and switching animations.

func updateAnimation

• create a variable to hold the name of the animation you decide to play

• change this value based on the velocity of the sprite

  • e.g. - if the velocity is greater than 0 set the animation to "walkDown"

• at the end of the function

  • refer to whatever variable is set to your $AnimatedSprite2D objct
  • call it's play function and pass the name of the animation you want to play
  • e.g. animations_node.play(animation_string_name)
• make sure to call this function from the physics process!!!

set end position to world scene marker

add marker 2D node to sprite

• go to world scene
• right click on sprite
• add a Marker2D node

• the marker pointer will be right on the sprite if you scroll in

  • grab the marker crosshair and move it to where you want

add Marker2D to the sprite script

• @export var endPoint: Marker2D
• add an export variable
• specify the type is Marker2D

assign Marker2D to endpoint

• the Sprite inspector will now show an EndPoint property

  • select the sprite

    

• go to world, and drag the Marker2D object to the EndPoint property in the inspector for sprite

  
• if you drag over the sprite object, then inspector will open up on that and you can move it over

in func _ready

• set endPosition to the global position of the endPoint marker

• global position is the actual position in the game

  • regular position is relative to teh nodes parents' position
• endPosition = endPoint.global_position

Video Contents

• 00:00 Introduction
• 00:19 enemy scene
• 00:59 AnimatedSprite2D
• 01:38 animations
• 03:15 add to world
• 04:13 pixel snap
• 04:32 enemy movement
• 07:26 change direction
• 08:27 update animation
• 09:05 adding variation
• 10:08 outro