Area2D detects a frame late

[jtw789]

Godot Version

4.6.stable

Question

I have this game that has a ‘mouse placement‘ node. It follows the mouse and previews where a tile will be if you place it. It has an area, and when that area is inside a ‘placeable tile‘ area it shows, but when it’s not, it hides.

The problem though, is that it hides a frame late:

Here’s the code:

func _process(_delta: float) -> void:
	mouse_placement.position = (round((get_global_mouse_position() - Vector2(25,25)) / Vector2(50,50))) * Vector2(50,50) + Vector2(25,25)
	mouse_placement.hide()
	
	if mouse_placement.get_node("Area2D").has_overlapping_areas():
		mouse_placement.show()
	else:
		mouse_placement.hide()

I’ve spent so many hours on this bug. All help appreciated!

[gertkeno]

The “hardware” mouse is handled by the operating system, getting it’s position does have a delay that may not be resolvable, especially without consolations. One such solution would be to draw your own “software” mouse by hiding the mouse Input.mouse_mode = Input.MOUSE_MODE_HIDDEN and updating a sprite2D to the mouse’s position every frame, much like you are doing now, but without the snapping (which you might be able to do better with .snappedf(50).

Here’s another thread on the subject, there have been a few but I understand they are hard to search for.

Mouse trail has 1-frame delay, is there anything I can do?

Godot Version 4.2.1 stable Question Hey, so I’m using a Line2D to make a mouse cursor trail, but as you can see in this gif: [cursor delay] EDIT: Yeah turns out the gif didn’t pick up my mouse cursor, but there’s almost always a gap between my mouse cursor (which is a white dot the same thickness as the beginning of the trail to blend in with the trail) and the trail It has a pretty egregious 1-frame delay. The docs say using a script to set the cursor would have a 1-frame delay So, my que…

[jtw789]

Okay. So I made a ‘mouse‘ node that goes to the mouse position and I hid the real mouse. I then made it so ‘mouse placement‘ goes to the ‘mouse’ node, but it still acts exactly the same. Did I do something wrong? Thanks for helping by the way.

[gertkeno]

Ah sorry I missed that your issue is with specifically hiding the object, that “if areas has overlapping areas”. It may be better to use _physics_process and signals as the _process (and all functions) run from top to bottom without stopping so there is no space fro the area to detect collision between your placement and your if statement.

[jtw789]

Now it looks like this:

func _physics_process(delta: float) -> void:
	$Mouse.position = get_global_mouse_position()
	mouse_placement.position = (round(($Mouse.position - Vector2(25,25)) / Vector2(50,50))) * Vector2(50,50) + Vector2(25,25)
	

And:

func _on_area_2d_area_entered(_area: Area2D) -> void:
	mouse_placement.show()

func _on_area_2d_area_exited(_area: Area2D) -> void:
	mouse_placement.hide()

Although it still acts the same.

[gertkeno]

Maybe execution order too? Is your area up or down from mouse_placement in the scene tree? I think if you can move the area down after mouse_placement it should process collision after each movement.

[jtw789]

Currently the area that is detecting the ‘placeable tiles‘ and has the functions that make ‘MousePlacement‘ show or hide, is the child of ‘MousePlacement.‘

But I did try making MouseArea2D not be a child of MousePlacement but rather be above or below MousePlacement but it didn’t change anything. I also tried moving the Mouse node around in the tree but no change.

[neozuki]

It might be from the physics server not immediately reflecting your change.

If so: You can change your code to use raycast or shapecast, and use the “force update” methods. Or in code get the physics state and do an immediate raycast.

Edit: by immediate (direct) queries I meant something like this: Ray-casting — Godot Engine (stable) documentation in English

[jtw789]

I’m not familiar with this. What exactly am I supposed to do?

[gertkeno]

Direct physics queries allow you to detect collision at any point in code without a node. The nodes require their own processing time where direct queries happen immediately.

Here’s a link to another post of mine with a sample using a ShapeQuery

Area2D Not Detecting Collision Soon Enough

That makes sense! Instead of using node-based collision you can query physics collisions from the world, though you may see better performance by keeping the query object between tree-spawns and only changing the position. func treeSpawn(): var world := get_world_2d().direct_space_state var query := PhysicsShapeQueryParameters2D.new() query.shape = tree_spawner_shape # A Shape2D resource, such as a CircleShape2D query.transform.origin = Vector2(randi_range(-1427, 1427), randi_range(-727, 72…

[jtw789]

Do you know of any tutorials I can use to learn about this?

[neozuki]

I don’t have a tutorial on hand, but the documentation I linked to is a short guide.

To summarize the problem: _process ticks away independently of our physics world. Sometimes you want to set things up, connect some signals, and let the physics world handle the nitty-gritty. Other times you would rather have instant information from the physics world.

For ray-casting, all you are doing is this:

• get the physics world (called a space state)
• set up some query: a point, a line (ray), a shape
• use the query to get a list of things you hit
• do stuff with the info

So you want mouse_placement to know when its inside a placeable_tile area. And you’ve got a CollisionShape2D on hand. Could try something like this:

#change this to point to the shape (not sure where your script is at in the tree)
@onready var shape: CollisionShape2D = $CollisionShape2D

func _physics_process(delta: float) -> void:
  $Mouse.position = get_global_mouse_position()
  mouse_placement.position = (round(($Mouse.position - Vector2(25,25)) / Vector2(50,50))) * Vector2(50,50) + Vector2(25,25)
  
  # 1. Get the physics world state
  var space_state = get_world_2d().direct_space_state

  # 2. Set up our query
  var shape_query = PhysicsShapeQueryParameters2D.new()
  shape_query.shape = shape
  shape_query.transform = mouse_placement.transform
  shape_query.collide_with_areas = true
  shape_query.collision_mask = 1 << 8 #change 8 to the physics_layer you've put `placeable_tile` areas

  # 3. Use the query and get a list (dictionary) of results
  var result = space_state.intersect_shape(shape_query)

  # 4. Do stuff with the info -- I guess in this case we don't care about how it collided, just that it did.
  if result.is_empty(): # we aren't touching a placeable area
    mouse_placement.hide()
  else:
    mouse_placement.show()

Might have made some typos. Assuming nothing weird with the transform, it should work.

[jtw789]

I get the following errors:

Parameter “shape” is null.

Condition “p_shape_ref.is_null()” is true.

[gertkeno]

the sample should be using a Shape2D, not a CollisionShape2D. You would have to @export this variable to set it in-editor

@export var shape: Shape2D

[jtw789]

@neozuki

@onready var shape: CollisionShape2D = $CollisionShape2D

So I should change : @onready var shape: CollisionShape2D = $CollisionShape2D

To : @onready var shape: Shape2D = $CollisionShape2D.shape ?

I tried that and the errors are gone, but it’s not detecting anything.

[gertkeno]

Do you have a Collision shape as a direct child? Can you share your new code?

[jtw789]

@onready var shape : Shape2D = $MousePlacement/MouseArea2D/CollisionShape2D.shape


func _physics_process(_delta: float) -> void:	
    $Mouse.position = get_global_mouse_position()
	mouse_placement.position = (round(($Mouse.position - Vector2(25,25)) / Vector2(50,50))) * Vector2(50,50) + Vector2(25,25)
	
	##
	var space_state = get_world_2d().direct_space_state
	
	var shape_query = PhysicsShapeQueryParameters2D.new()
	shape_query.shape = shape
	shape_query.transform = mouse_placement.transform
	shape_query.collide_with_areas = true
	shape_query.collision_mask = 3
	var result = space_state.intersect_shape(shape_query)
	
	var touching_placeable = false
	if result.is_empty():
		touching_placeable = false
		mouse_placement.hide()
	else:
		touching_placeable = true
		mouse_placement.show()
	##

I’m going to use touching_placeable elsewhere.

[gertkeno]

@jtw789

shape_query.collision_mask = 3

Do you intend to hit layer 3 or both/either layers 1 and 2? Currently this line detects layers 1 and 2, not 3. If you wanted 3 you could write 0b100 or 1 << 2

It may also help to move some of the query parameters to _ready so you aren’t creating new objects and duplicate work each frame

@onready var shape : Shape2D = $MousePlacement/MouseArea2D/CollisionShape2D.shape
var shape_query := PhysicsShapeQueryParameters2D.new()

func _ready() -> void:
	shape_query.shape = shape
	shape_query.collide_with_areas = true
	shape_query.collision_mask = 0b100

func _physics_process(_delta: float) -> void:
	# etc...
	var space_state = get_world_2d().direct_space_state
	shape_query.transform = mouse_placement.transform
	var result = space_state.intersect_shape(shape_query)
	# etc...

[jtw789]

Yes!!! It’s working! Thank you so much @gertkeno and @neozuki for your time. I really appreciate it.