Strange issues with Look_At() regarding mouse position accuracy

Lethn

I'm having some strange issues with rotating a Raycast2D node towards the mouse, it seems to be offset by exactly 90 degrees. When I put my mouse cursor to the bottom of the character it sets the rotation to 90 degrees then when I go to 90 degrees it sets to -180 to the top of the character.

Even weirder when I rotate the raycast to the left of the character the collision seems to stop colliding with the tiles entirely which makes me wonder if the raycast is somehow flipping as a result of the strangeness going on with look_at() . Does anyone have any idea what's going on with this?

extends RayCast2D

var tileMap
var mousePosition = Vector2()
onready var playerRaycast = get_child(0)

func _ready():
	tileMap = get_tree().get_current_scene().get_child(1)
	print(playerRaycast)
	
func _physics_process(_delta):
	
	if is_colliding() and Input.is_action_just_pressed("LeftClick"):
		var cell = tileMap.world_to_map(get_collision_point())
		var cell_ID = tileMap.get_cellv(cell)
		if (cell_ID == 0):
			tileMap.set_cellv (cell, 1)
		if (cell_ID == 1):
			tileMap.set_cellv (cell, 2)
		if (cell_ID == 2):
			tileMap.set_cellv (cell, -1)
	
	mousePosition = get_global_mouse_position()
	look_at(mousePosition)

By all accounts this should be very straight forward code but I've had nothing but issues, if it helps any I recently downloaded 3.3 but I had these exact same problems in 3.2

GlyphTheWolf

Hi,

Is your raycast facing up by default?

Godot coordinates assume 0 radians to be facing right. When I tested that with look_at it seems to be working as expected.

Lethn

LOL thanks for that explanation, I just managed to fix it by casting the raycast along the X axis rather then the Y axis and the accuracy of the raycast seems to be perfect now for the movement at least so it looks like that was just a setup issue with my nodes. I still have a strange problem with the collision on the left not working though.

GlyphTheWolf

Hm, that's strange. In my test collisions seems to be working properly even after raycast rotation.

It's hard to say what may be cause it doesn't work for you. Probably you need to do some debugging yourself or post project where issue is reproduced to find cause.

Lethn

Maybe I need to start over with the node setup from scratch, could be another issue from that if simply changing cast to to the X axis fixed the other issue, will check the tutorials I've been looking at and see if they've got different settings to me.

Lethn

My mind has been blown by this one, I'm still not able to get the raycast to collide with the tiles to the left of the player even though it works completely fine on the right. Does anyone maybe want my project file to look at so they can see where I've caused the bug? Can't think of anything else I might have done wrong, just to double check it wasn't anything strange with the camera I got rid of that and had it on the default view, that didn't do anything either.

GlyphTheWolf

I could check it in free time. I am curious what may be cause of that because my simple project also use tilemap (with collisions) and rotated raycast and I had not issues with collision checks, so that's interesting what may be reason.

Lethn

https://racaty.net/eymepqaylosp

Here's a link to the project for anyone that's interested, I just zipped for the sake of it being easier to download, should just be a matter of drag and dropping into wherever you've saved the Godot projects. Given the nature of Godot I don't know whether I've just messed up the setup or I somehow managed to stumble across a genuine bug.

GlyphTheWolf

Hi,

I checked your project and it seems issue is pretty easy to solve.

Whole issue is not connected with wrong collision detection, but more with rounding values.

When you use get_collision_point() it will return exact position where collision happened. When you hit block from its side (left or right) position X will be set to X of block side. And now, because blocks are placed into grid that returned X will be always on boundary between 2 cells. It seems Godot in method world_to_map() assume that full X value to be already next cell and that is why collision on right side are working fine, but on the left side doesn't work (because of that rounding always cell on the right of collision is returned by world_to_map())

Here is some image to illustrate that issue: The same point is returned when you hit cell (1, 0) from left side and when you hit cell (0, 0) from the right side, but in first case it will work as expected since (1, 0) cell will be returned, however in second case the same cell (1, 0) will be returned, but you actually hit cell (0, 0).

I fixed that issue by altering returned value like that: var collisionPos = get_collision_point() - get_collision_normal() * 32. I just subtract half of the tile size according to hit normal to assure position will be "somewhere inside cell" instead of the border area which may cause rounding issues.

Lethn

holy crap @GlyphTheWolf, thanks for the detailed explanation there, had no idea about any of that, I'll do some experimenting with that to get it all to work. It's interesting you mentioned normals because I tried doing get_collision_normal() just to see what would happen and the collision just broke entirely. I also initially thought that maybe the raycast was already colliding through the player on the left side and maybe that's why there were problems. It looks like the maths was a little bit more complicated than I thought.

Lethn

Just to double check the maths that you showed me @GlyphTheWolf and satisfy my own curiosity I set up some standard rigidbodies to see if the raycast would behave itself on both axis compared to when I use the tilemap code combined with look at the way I originally did before Glyph gave his explanation.

extends RayCast2D

var tileMap
var maxDistance = 30
var diggingCountDown = 3
onready var playerRaycast = get_child(0)

func _ready():
	tileMap = get_tree().get_current_scene().get_child(1)
	
func _physics_process(_delta):
	
	
		
    	if is_colliding():
    		if Input.is_action_just_pressed("LeftClick"):
    		#	var cell = tileMap.world_to_map(get_collision_point() - get_collision_normal() * 32) correct tilemap code
    			var cell = tileMap.world_to_map(get_collision_point())
    			var cell_ID = tileMap.get_cellv(cell)
    			if (cell_ID == 0):
    				tileMap.set_cellv (cell, 1)
    			if (cell_ID == 1):
    				tileMap.set_cellv (cell, 2)
    			if (cell_ID == 2):
    				tileMap.set_cellv (cell, -1)
    			if (cell_ID == 3):
    				tileMap.set_cellv (cell, 4)
    			if (cell_ID == 4):
    				tileMap.set_cellv (cell, 5)
    			if (cell_ID == 5):
    				tileMap.set_cellv (cell, -1)
    				
    			var raycastTarget = get_collider()
    			if raycastTarget.is_in_group("Boulder"):
    				print("Boulder Detected")
    				
    	look_at(get_global_mouse_position())

Low and behold, the rigidbodies worked absolutely fine and the raycast interaction with the tilemap broke itself again so now thanks to the explanation I consistently understand the way raycasts interact with TileMaps compared to standard rigidbodies and other nodes in the engine. Godot can be extremely fussy when it comes to the maths but at least it all works perfectly when you get everything setup right.

Hope this helps out anyone who's been having similar issues.

GlyphTheWolf

Actually I think each tile in TileMap is treated by Godot as separate StaticBody (not sure about that, maybe some optimizations are done for that). When you check collision with RigidBody it will work the same, it will return collision point somewhere on the RigidBody edge, but unless you use that value in some calculations where rounding may cause issue it will be fine. I guess if your collision for tiles would be setup to not take whole tile space (be smaller from each side a bit) then your first approach would also work fine.

Edit: 2 more tips. In Godot 3.3 if you turn on collision shapes debug display raycasts are also rendered as arrows. In your TileMap you can check option to display collision shapes also (when mentioned before option is enabled).

Lethn

https://rumble.com/vg5u8l-free-sci-fi-2d-platformer-wip-1.html?mref=16ov1&mrefc=2

It's all working now Glyph, thanks, I made posts about this and linked here and also gave you a mention since the information you gave explained a lot.