How to make two lerp with different "to" values to reach it at the same time?

[adrien.h]

Godot Version

Godot 4.2.1.stable

Question

Hi!

I have two lerp functions, which operate two different parts of my character. I need them to reach their “to” value at the same time, while the “to” value is always different for both lerps.

# Here the player adjusts the swingForce and dragForce variables to a value of 0.0 to 1.0.

	if Input.is_action_just_pressed("space") && not throwingBall :
		throwingBall = true
		setSwingForce = swingForce
		setDragForce = dragForce

# Here I have a function that lerps swingForce and dragForce back to 0.0 . setSwingForce and setDragForce saves the values the player has registered.

	if throwingBall:
		swingForce = lerp(swingForce, setSwingForce, 0.1)
		dragForce = lerp(dragForce, setDragForce, 0.1)

Please let me know if anyone has a more optimal way to achieve this. Or maybe an equation to put in the “weight” argument, with the variables given.

Thanks!

[kahshmick]

Typically when you lerp between points you have A(start point), B(end point), and T(Percentage between A and B). However in your code with each call of the lerp function here you’re actually modifying the value of A. I’m assuming this is to make a cool curve where it slows down the closer it is to it’s destination . The side effect of this is that the “lerping” will NOT take a specified time, and A will actually never reach the “To” value, instead getting infinitesimally close.

Interpolation

If I wanted to do vanilla linear interpolation between values, here’s what I’d do.

var throwingBall : bool

var startSwingForce : float
var endSwingForce : float

var startDragForce : float
var endDragForce : float

var swingForce : float
var dragForce : float

var lerpT : float # value between zero and 1
const lerpDuration : float = 5 # How long the lerp will take in seconds


func _process(delta):
	if Input.is_action_just_pressed("space") && not throwingBall:
		throwingBall = true
		lerpT = 0
		startSwingForce = swingForce
		startDragForce = dragForce

	if throwingBall:
		lerpT += delta / lerpDuration
		swingForce = lerp(startSwingForce, endSwingForce, lerpT)
		dragForce = lerp(startDragForce, endDragForce, lerpT)
		if lerpT >= 1:
			# at this point your lerp is done, swingForce == endSwingForce
			throwingBall = false

[adrien.h]

Works perfectly, many thanks @kahshmick!

I think I’m getting it, I will continue doing researches on lerps. Thanks for the explanations too!