Weird camera rotation (stuttering very quickly) when used with move_and_slide

kl3psydra

Hello, I am new to Godot3D and trying to follow the tutorial here:

I have a KinematicBody as the player and I'm getting this weird issue where the camera freaks out and rotates very quickly (stutters between two different angles) when using move_and_slide. The script is very basic:

extends KinematicBody

export var _mouse_sensitivity: float = 0.20

func _ready() -> void:
	Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED)


func _input(event) -> void:
	aim(event)

func _physics_process(delta):
	var movement_vector: Vector3
	
	if Input.is_action_pressed("move_forward"):
		movement_vector = Vector3(0, 0, 1)

	move_and_slide(movement_vector)

func aim(event: InputEvent) -> void:
	var mouse_motion = event as InputEventMouseMotion
	if mouse_motion:
		self.rotation_degrees.y -= mouse_motion.relative.x*_mouse_sensitivity
		
		var current_tilt: float = $Camera.rotation_degrees.x
		current_tilt -= mouse_motion.relative.y*_mouse_sensitivity
		
		$Camera.rotation_degrees.x = clamp(current_tilt, -180, 0)

This issue doesn't occur if I comment out the y-axis rotation or move_and_slide. I've tried locking the fps and disabling vsync, but looks like something else is the issue. Any help would be appreciated!

TwistedTwigleg

Welcome to the forums @kl3psydra!

If I had to guess, its probably that the physics engine doesn't like that you are rotating the KinematicBody node outside of _physics_process, because it makes the physics engine and the game data out of sync.

I would recommend a node for adjusting the Y rotation of the camera, so that you can rotate it independently of the rotation of the KinematicBody node. For example, you could use a scene setup like this:

Player_Root
- Cam_Rot_Y
  - Camera

Then on line 23 you can rotate the new node (Cam_Rot_Y) instead of rotating the KinematicBody node. I've done this a few times for some games I've made and I have not ran into any issues doing it this way.

If I recall correctly, I did a setup like this for the game jam version of Dreams of Fire, which you can find the source code on GitHub if you want to take a look and use it as a reference. The code is old (over 3 years old!), not at all documented, and written in a hurry. Also, because its so old you may need to use Godot 3.0 or 3.1, but it should hopefully show a working reference.