getting_started/first_2d_game/04.creating_the_enemy

[giscus[bot]]

getting_started/first_2d_game/04.creating_the_enemy

Now it's time to make the enemies our player will have to dodge. Their behavior will not be very complex: mobs will spawn randomly at the edges of the screen, choose a random direction, and move in...

https://docs.godotengine.org/en/stable/getting_started/first_2d_game/04.creating_the_enemy.html

[ThomasCrane]

C# users must change the connections under the Node tab to C# nomenclature, not the default it provides you.

Change _on_visible_on_screen_notifier_2d_screen_exited to OnVisibleOnScreenNotifier2DScreenExited, or, if you've already created the script as guided, you can select the Pick button to the right of the text field when editing the connection, and then select the appropriate method.

[Wadahell]

I need help with the enemy animations.
They appear when i'm fitting the hitbox, but not when I run the scene

[Wadahell]

That's not the problem, it works on the 2d scene and dont on the game.
And also, it doesnt randomize, it only uses the last animation i edit, like if i click on Swim, he only shows the swimming mob on the game and without the animation
Also got a weird Break point in the line
$HUD.show_message("Get Ready")

my game doesnt run if this is in the code

[SeanSan06]

This is late but it could be because your running the player scene and not the mob scene

[oulfik]

I'm also late to the party: I had the exact same problem. In my case I forgot to attach the mob script to the node. You have to check this in the Inspector view at the bottom.

[IrwinKwan]

I had the same problem as well. I fixed it by enabling "Autoplay on load", which looks like an arrow with an "A" in it.

[AetherialAvenger]

Insert $AnimatedSprite2D.play() below $AnimatedSprite2D.animation = mob_types.pick_random()

$AnimatedSprite2D.animation = mob_types.pick_random() only tells the node to SET a specific animation

You still have to tell it to PLAY the animation with .play()

[PamProg]

When you say to "To align the shape with the image", not all sprites have the same size, but we only use 1 AnimatedSprite2D, shouldn't we use one for each ?

[BastardSeagull]

I just based it on the swimming one, but you probably could do a different one for each. I'm new to Godot, but I can't think of a way to do it without creating 3 separate mobs and updating on_mob_timer_timeout() to select one instead of having the selection in the mob script.

Might be a fun way to try to expand on the project!

[SolarLunix]

I created two 2D Collisions and called them Collision_WalkSwim and Collision_Fly I leave Collision_WalkSwim alone. Collision_Fly just goes around the legs.

func _ready() -> void:
	var mob_types = $AnimatedSprite2D.sprite_frames.get_animation_names()
	var mob_type = mob_types[randi() % mob_types.size()]
	$AnimatedSprite2D.play(mob_type)
	if mob_type == "fly":
		$Collision_Fly.disabled = false
	else:
		$Collision_Fly.disabled = true

Hopefully it works.

Edit: Appears to work just fine :D

[MoroAstray]

What does the Collision Mask mean? It just says to uncheck the 1 but it feels really random with no explanation

[BastardSeagull]

The collision mask is where it looks for what it's colliding with. So by unchecking 1, it's not bothering to check if it's touching anything.

[vmorris]

What do the other mask values do?

[Calinou]

What do the other mask values do?

By default, only the layer 1 is used. You can add objects to other layers to have more granular collision behavior (e.g. have the player collide with a certain object, but have enemies phase through this object instead).

Other mask values will only have a noticeable effect if you have at least one object on that layer.

[JoemanJ]

To expand a bit on this explanation, you can think of collision layers and mask this way:
If an object is active on LAYER 1, that means it can "hit" objects in layer 1;
If an object is active on MASK 1, that means it can "be hit by" objects in layer 1.

The way the collisions are configured in this tutorial basically means that "enemies can hit a player (because the enemies are active on LAYER 1 and the player is active on MASK 1) but an enemy can't hit another enemy (because the enemies aren't active in any MASK)"

[BytesBlade]

This explanation needs to be in the doc

[YoungBacC]

Make sure to set the collision shape 2D on the mob or else it will not work when it hits the player. I know this is obvious, but I forgot LOL.

[vmorris]

Connect the screen_exited() signal of the VisibleOnScreenNotifier2D node to the Mob and add this code:

This has me going :hmm:

I know you just explained how to do this in the previous section, but maybe you could give alittle more context?

[vmorris]

Like... what is "queue_free"?

[vmorris]

Answering my own question here.. maybe this was given in a previous section of the getting started?

Unlike with Object.free(), the node is not deleted instantly, and it can still be accessed before deletion. It is also safe to call queue_free() multiple times. Use Object.is_queued_for_deletion() to check if the node will be deleted at the end of the frame.

Note: The node will only be freed after all other deferred calls are finished. Using this method is not always the same as calling Object.free() through Object.call_deferred().

[Andrewjdesigner]

This part confused me too. For people like me, taking breaks between sections, screen_exited() is a signal built into the VisibleOnScreenNotifier2D node. Select VisibleOnScreenNotifier2D in the scene tree. Then, click the Node tab next to the Inspector. There you'll find the screen_exited() signal. Right-click and select connect to connect it to your Mob node.

[GalaxyBangBang]

Why do you use RigidBody2D as the root node of mob, but use Area2D as the root node of player? Are there any differences? Thanks for any responses.

[GalaxyBangBang]

I find a blog and it answers my problem, https://code.luasoftware.com/tutorials/godot/godot-area2d-vs-staticbody2d-ve-rigidbody2d-vs-kinematicbody2d. In short, you use force to control rigidbody but you use setPos to control area 2D.

[JoemanJ]

In general, you should choose the node type what will be "easier to control" for your objects.

In this case, because the way the enemies move (which is defined in the next section), it is easier to just "give them a push" in some direction and have them moving on their own (or rather, have the physics simulation move them for us) instead of update their positions ourselves like we did with the player, so we chose 'RigidBody2D' in their case.

You are correct in the idea that 'RigidBody2D' is to be "moved by aplying force" and that 'Area2D' is to be "positioned" (props to you for doing your own research and posting your answer to others btw). You can think of an 'RigidBody2D' object's movement as a ball being pushed around, while a 'Area2D' object's movements would be more like the same ball being grabbed and moved

[kjosh]

In these examples I often see repeated uses of $AnimatedSprite2D. As far as I understand it this is syntactic sugar as an alias for get_node("AnimatedSprite2D").

In real projects, is it worth it to assign the node to a variable and reuse that instead of repeatedly calling get_node in a hot code path, or is the call so cheap that I shouldn't usually bother and prefer the better readability?

[Calinou]

In real projects, is it worth it to assign the node to a variable and reuse that instead of repeatedly calling get_node in a hot code path, or is the call so cheap that I shouldn't usually bother and prefer the better readability?

Yes, the get_node() call is cheap but it's not free. Also, assigning it to a variable makes it easier to benefit from static typing, which can provide further performance benefits thanks to typed instructions:

# NOTE: The type must be mentioned explicitly.
# Type inference (`:=`) cannot be used for a precise type hint (unless casting with `as`).
# Otherwise, it will just be a Node type hint.
var sprite: AnimatedSprite2D = $AnimatedSprite2D

[madddmadd]

I set my gravity scale to 0 on the rigid body and the enemy still falls and i cant seem to figure out why

[jeroenriess]

The _on_body_entered function is never being called. I followed this tutorial closely.
Here's information about my setup which I think is important for collisions:

• Player is type Area2D
• Player has CollisionShape2D drawn around the entire body
• Player has collision layer 1, mask 1
• Mob is of type RigidBody2D
• Mob also has a CollisionShape2D drawn around entire body
• Mob has collision layer 1, and no mask

I set "Debug > Visible collision shapes" so that I can clearly see the shapes overlapping.
I have a print statement in the _on_body_entered, and nothing is printing, so this function is clearly not running.
The _on_body_entered function seems to be linked correctly to the signal.
I am even printing "body_entered.is_connected(_on_body_entered)" at every cycle and get true as output.

Any other ideas to debug this issue? Thanks.

[jeroenriess]

I found my issue...
In the Player start() function, I wrote: $CollisionShape2D.disabled = true instead of false.

[PaulRS747]

When I type extends Rigidbody2D in mob, if it already has extends Area2D then it generates an error, but if I change the extends Area2D to Rigidbody2D it makes the same change also in player. I do not know how to proceed.

[kotsaris]

Keep in mind that the OnVisibleOnScreenNotifier2DScreenExited method has to be public for the Pick button to work on the Connect dialog. If you have it Private, like in the Tutorial above, it won't be detected.

[somebarcode]

For some reason the enemy Mobs collide and bounce off each other's Mobs.

How can the Mobs fly around without crashing next to the other ones? Not sure where I've caused them to collide.

[stefangorneanu97]

Make sure you Select "RigidBody2D" > Collision > Click on Mask (1) so it is NOT highlighted. This prevents them from colliding with each other.

[ElectricZax]

In CollisionObject2D we disable "Mask 1", so that the enemies can go through one another, correct?
The "Mask 1" is enabled on the Player, so that it gets hit...
How can I specify or differentiate from hits from Mask 1 or Mask 2, so I can create different actions for different situations?

For example something like _on_body_entered.mask_1() ?

[ElectricZax]

I tried to switch up things a bit, but have a problem...
Since the Mob scene (RigidBody2D) has "body_entered" as signal, I tried to setup the body entered signal in Mob instead of in Player. But it doesn't work. It looks like the "body_entered" is ignored and nothing happens. Any ideas why?

[FunkyToc]

Note that the "%" means "modulo operator" (and not a specific/weird keyword thing)

randi() % mob_types.size()

So, you can read this as:

• randi() take a random interger between 0 and 2^32
• % modulo (math operator, like * / + -)
• mob_types.size() size of our array

You could use this as an equivalent without using modulo:
randi_range(0, mob_types.size() - 1)

[RockyKev]

The demo project and the tutorial has different code and it should be synced.

In the tutorial:

func _ready() -> void:
	var mob_types = $AnimatedSprite2D.sprite_frames.get_animation_names()
	$AnimatedSprite2D.play(mob_types[randi() % mob_types.size()])

Where the demo project's mob.gd is:

func _ready():
	$AnimatedSprite2D.play()
	var mob_types = Array($AnimatedSprite2D.sprite_frames.get_animation_names())
	$AnimatedSprite2D.animation = mob_types.pick_random()

[Selenestica]

A .gif showing how the mobs should behave at the end of this part of the tutorial would be super helpful. When I run this script, I have one mob in the upper left corner of the screen doing it's animation. I'm not sure if this is correct or not.

[Crysteier]

Edit for I gave the worng anser before:
the mob will not behave like anything. In this module you just setup how the mob will behave in the next section of this tutorial. Just keep on going and you will see it.

[kjenney]

In addition, under the CollisionObject2D section just beneath the RigidBody2D section, expand the Collision group and uncheck the 1 inside the Mask property. This will ensure the mobs do not collide with each other.

This took me a little bit to figure out because I had already named RigidBody2D to Mob.

[jpkloess]

I'm running into a roadblock with this tutorial in Godot 4.3. I'm actually on the following step of the tutorial (The main game scene), and my game is crashing every time I run it with the error: "Invalid call. Nonexistent function 'get_animation_names' in base 'AnimatedSprite2D'."

The mobs do not spawn along my path or anywhere else, and the game just crashes. Is there a new getter I need to make this work?

[jpkloess]

Edit: I can confirm the issue is the animation. If I comment out the code in "func _ready()" the mobs spawn as intended. No idea why the animation get is not working though.

[boertv]

Did you forget sprite_frames maybe? Like this $AnimatedSprite2D.sprite_frames.get_animation_names()

[phicar2]

I had the same error...and my mistake was that I missed the 's' in 'names'
I had: $AnimatedSprite2D.sprite_frames.get_animation_name()
instead of: $AnimatedSprite2D.sprite_frames.get_animation_names()

[feihuan1]

extends RigidBody2D

func _ready() -> void:
	var mob_types = $AnimatedSprite2D.sprite_frames.get_animation_names()
	$AnimatedSprite2D.play(mob_types[randi() % mob_types.size()])

func _on_visible_on_screen_notifier_2d_screen_exited() -> void:
	$CollisionShape2D.set_deferred("disabled", true)
	queue_free()

is it neccesary use set_deffered here?

[Calinou]

Yes: https://docs.godotengine.org/en/latest/classes/class_collisionshape2d.html#class-collisionshape2d-property-disabled

(This is also the case in 3D.)

[TheLongCorgi]

For anyone else looking for why the animation isn't playing: You need to add

$AnimatedSprite2D.play()

under

func _ready():

It should look like:

func _ready():
	$AnimatedSprite2D.play()
	var mob_types = Array($AnimatedSprite2D.sprite_frames.get_animation_names()) #sets an array called "mob_types" with a list of items that are the names of the animations
	$AnimatedSprite2D.animation = mob_types.pick_random() #picks a random mod type from the array

[Calinou]

This was added to the documentation in godotengine/godot-docs#10752, but it hasn't been cherry-picked to stable yet.

[atollk]

As an alternative, enable "Autoplay On Load" on the animation frames.

[atollk]

I feel like this guide is missing a step to resize the VisibleOnScreenNotifier2D node. When I created it, it was like a 10x10 rectangle which caused the the mobs to despawn at the edge of the screen while still visible. The node rect has to be resized to include the entire mob sprite.

[droy117]

Shouldn't we add $AnimatedSprite2D.play() here? Without this the mob is not animating in my Main scene.

func _ready():
var mob_types = Array($AnimatedSprite2D.sprite_frames.get_animation_names())
$AnimatedSprite2D.animation = mob_types.pick_random()
$AnimatedSprite2D.play()

[Calinou]

This was already discussed above: #82 (comment)

[droy117]

Yes sorry, I missed it.

[TheDeadMeasure]

I'm trying to set up my mob nodes, and to make the children unselectable (per "Don't forget to set the children so they can't be selected, like you did with the Player scene."), but I don't have that icon (or any icons) showing up beside the mob root node. I didn't have a problem with setting up the Player scene. I can't figure out how to get that icon to show up, or to find it in options somewhere.

[TheDeadMeasure]

I continued on, and when I moved the AnimatedSprite2D away from the other nodes (because I hadn't grouped them), then hit control z to bring the sprite back on top of the rest, the icon finally showed up in the window bar. I'm not sure if I did something wrong to begin with.

[zancorin]

Hmm, the CollisionShape2D can be aligned nicely with the swim and walk sprite animations, but not with the fly one... I guess since this is an earlier tutorial, I shouldn't worry about accuracy too much?

[Nowell5]

So my mob is using the animation in the game, but the mob is just flying across the screen. What's up with that? The mob is not going through it's animation cycle properly and as soon as it enters the area it instantly falls and does not go across the screen as intended.

[Nowell5]

Alright so I fixed it, I went into project settings went to physics, clicked on 2D and set my default gravity to 0.0. It was set at 980 that is why my mobs were instantly dropping to the ground as soon as they spawn into the map !