is_on_wall and on_Area2D_body_entered in conflict?

trevbot

Hello!

I am presently trying to create a destructible box in a 2D platformer.

Up to this point, I have a projectile object which, when it hits a piece of terrain with is_on_wall (or is_on_floor, or is_on_ceiling) it destroys itself.

Now I want to have the "destructible box" object detect the projectile, and the recommended method for doing this seems to be to create an Area2D and use on_Area2D_body_entered.

However, what seems to be happening is that the projectile destroys itself before the body enters the Area2D (which makes sense). What surprises me is that I can't just extend the Area2D by a single pixel and have the detection register, and instead have to stretch it out by a whole 4 pixels, which means the projectile is pretty far away from the box when damage/destruction is registered.

I'm assuming the answer to this is that "is_on_wall isn't great" and I should be using something else to detect terrain blocks for my projectile. But since the built-in function seems very convenient so far, I was hoping there might be another solution that wouldn't require me to code custom detection. In particular, I was hoping I could detect the collision (rather than the "entered area") to trigger the damage/destruction of the box, but I haven't found anything like that.

Relevant code:

# PROJECTILE
func _ready():
	projectileVelocity.x = PROJECTILE_VELOCITY * projectileDirection
	$Sprite.play("default")

func _physics_process(delta):
	if(stuckCheck == position.x):
		queue_free()
	stuckCheck = position.x
	if(is_on_wall() || is_on_floor() || is_on_ceiling()):
		queue_free()
	
	projectileVelocity = move_and_slide(projectileVelocity, Vector2.UP)

# DESTRUCTIBLE BOX
func _on_Area2D_body_entered(body):	
	print("colliding") # Obvious placeholder is obvious.

(Apologies for the lack of tabbing, I don't quite understand why the code is formatting this way.)

Megalomaniak

trevbot (Apologies for the lack of tabbing, I don't quite understand why the code is formatting this way.)

Because you were tagging each part individually, but also you used two ` rather than the 3 needed for a code block as so ```. one of these three on a line preceding and one after the code block. for inline code like so you would use one ` in front of the code on the same line and one after it on the same line.

Megalomaniak

Have you tried using call_deferred() on the queue_free()?

trevbot

Because you were tagging each part individually, but also you used two ` rather than the 3 needed for a code block

Now that you say it, it seems obvious. I feel dumb, but educated. 😃

Have you tried using call_deferred() on the queue_free()?

I have not! I'll have to read up on that. Thank you!

Also, a follow-up question: does is_on_wall ignore mask layers? It seems like it triggers even when the projectile touches objects on layers that aren't enabled for interaction.

Megalomaniak

trevbot does is_on_wall ignore mask layers?

Never even thought about it before but I would expect so, since it's sole purpose is to determine if a surface would count as wall as opposed to counting as a floor for an example.

trevbot So call_deferred didn't seem to do the trick, but I altered the projectile code to hide the sprite and start a timer for 10 steps before running queue_free which seems to give it time to trigger the code on the box.

Not sure if just hard-coding a timer is the most elegant/memory-respecting solution, but it's working for now.

If it works, it works. Unless real issues stem from it I'd say it's valid.

trevbot

So call_deferred didn't seem to do the trick, but I altered the projectile code to hide the sprite and start a timer for 10 steps before running queue_free which seems to give it time to trigger the code on the box.

Not sure if just hard-coding a timer is the most elegant/memory-respecting solution, but it's working for now.

Current projectile code:

func _ready():
	projectileVelocity.x = PROJECTILE_VELOCITY * projectileDirection
	$Sprite.play("default")
	selfTerminateTime = SELF_TERMINATE_TIME

func _physics_process(delta):
	if(selfTerminateActive):
		if(selfTerminateTime > 0):
			selfTerminateTime -= 1
		else:
			queue_free()
	if(stuckCheck == position.x):
		queue_free()
	stuckCheck = position.x
	if(is_on_wall() || is_on_floor() || is_on_ceiling()):		
		queue_free()
	
	projectileVelocity = move_and_slide(projectileVelocity, Vector2.UP)

func _on_Area2D_body_entered(body): # Area2D in this case is the destructible box
	print("projectile collide")
	setSelfTerminate()


func setSelfTerminate():
	$Sprite.queue_free()
	selfTerminateTime = SELF_TERMINATE_TIME
	selfTerminateActive = true