Help with physics!

[Alike_Dev]

Godot Version

4.2.2

Question

I’m trying to get an NPC in my game to move or simulate the movement of a turtle. To do this I think I need to apply a force or an impulse in the direction I want it to move, but I’ve been reading and I haven’t found a method with which I can do this to a CharacterBody2D, am I forced to use a RigidBody2D? Any help would be greatly appreciated!

[gertkeno]

I don’t think you need to use forces for this. For a character body 2d you can set velocity then use move_and_slide() inside a _physics_process function override.

Could you share any code you have so far?

[Alike_Dev]

I don’t know why, but I have the idea that when I use move and slide it will either keep moving or it won’t stop fast enough, I don’t know if I can explain myself. The movement of a turtle starts when it is at rest, then it has an acceleration, it moves, until it loses its speed and falls back to rest.

[gertkeno]

You would have to manually adjust the velocity of a CharacterBody2D. If you do want physics-like behavior then a rigid body 2d will help and you can use apply_central_impulse(direction * speed) to give it a kick.

[Alike_Dev]

The movement I want it to make I try to describe in that drawing, the green line represents the speed, at first it increases and then decreases, until it reaches zero. Anyway I will try to do it with the move_and_slide() method

[gertkeno]

You can control “damping” on a rigid body, but the speed will increase faster than that curve. If you want exact control I would recommend a CharacterBody2D, you could even draw this as a Curve and use sample_baked to deduce speed and multiply direction.

Something along these lines lets you draw a curve as an exported property.

extends CharacterBody2D

@export var speed_curve: Curve
@export var speed_curve_duration: float = 2.0
@export var maximum_speed: float = 200
var speed_sample_position: float = 0.0


func start_movement() -> void:
	var tween := create_tween()
	tween.tween_property(self, "speed_sample_position", 1.0, speed_curve_duration).from(0.0)


var direction: Vector2
func _physics_process(delta: float) -> void:

	if direction:
		var speed: float = speed_curve.sample_baked(speed_sample_position) * maximum_speed
		velocity = speed * direction
	else:
		velocity = velocity.move_toward(Vector2.ZERO, maximum_speed * delta)
	
	move_and_slide()

[Alike_Dev]

This worked for me, it looks pretty much like what I want, thanks a lot