Making player move in 2D using Lerp

[dire veldt]

hi

anywaay

here's currently what my goal is

eh one sec

[fringe igloo]

might wanna formalize your question in one paragraph

[dire veldt]

I want it such that if the player holds down a key, a speed value is lerped until it hits a max speed, and holds that same speed until the key is let go, after which it lerps back to it's previous value (before the keypress)

here's my code so far (broken)

[fringe igloo]

float targetFloat = keyPressed ? 1f : 0f;
myFloat = Mathf.Lerp(myFloat, targetFloat, Time.deltaTime * lerpSpeed);

[fringe igloo]

or MoveTowards or whatever smoothing/lerping you want

[night bane]

This way it will never reach the target float though.

[dire veldt]

and how exactly do i control lerpspeed

i would like it so that it lerps from start to finish in around 0.5 seconds

[night bane]

There's no such thing as lerp speed. Lerp is a function that returns a value based on the parameters you give it.

[dire veldt]

right then is there a way i can use time.deltaTime inside the lerp and a timer of sorts

i attempted that on my script but couldn't figure out how to put it inside the lerp function

[night bane]

Lerp returns value between A and B based on time t within ranges of 0 to 1. So if you want it to lerp in .5 sec, then increment the t from 0 to 1 in .5 sec.

[fringe igloo]

private float transition;
[SerializeField] private float transitionSpeed = 10f;
[SerializeField] private float minValue = 3f, maxValue = 5f;
public float myFloat;

void UpdateMyFloat()
{
  // Transition value moves between 0..1 depending on key press state
  float  transitionTarget = keyPressed ? 1f : 0f;
  transition = Mathf.MoveTowards(transition, transitionTarget, Time.deltaTime * transitionSpeed);

  // Update myFloat to be between min and max value, in range of transition
  myFloat = Mathf.Lerp(minValue, maxValue, transition);
}

[dire veldt]

where is the myFloat used in the script?

[night bane]

t += delta time / desiredLerpTime;

[dire veldt]

and t goes inside the lerp, right?

[night bane]

Basically what Osmal shared.

[dire veldt]

i'll try to implement it

wait

does Mathf.MoveTowards work like lerp but uses time values?

[night bane]

None of them have to use time values. They are just functions that take input and return a value.

They just do simple math, like x = a + b.

You can use time in your calculations, but that's not gonna change the fact that they just do simple math every frame

[fringe igloo]

myFloat would be your result (green line in your drawing)

[dire veldt]

okay i understood the script i think

can i just say it from what i understood just to make sure

transition = Mathf.MoveTowards(transition, transitionTarget, Time.deltaTime * transitionSpeed);
this line is instantanouesly set to 0 if button not pressed, or slowlys goes to 1 (but never reaches it(??)) if the button is pressed

[fringe igloo]

I updated the snippet a bit so its easier to tell whats local vars and whats member vars

[fringe igloo]

it moves the transition float over time. It moves it towards 0 if no key is pressed, and 1 if key is pressed.

and it does reach the target value yes

then we use transition to "sample" a value between minValue and maxValue

(with Mathf.Lerp)

[dire veldt]

does it move at a rate of 0.01

like if I'm running at 60fps then time.deltaTime ~ 0.01 right

[fringe igloo]

are you talking about the MoveTowards line?

[dire veldt]

yes

[fringe igloo]

if you use Time.deltaTime as t in MoveTowards, it will take 1 second to reach the value

if you use Time.deltaTime * 10, it will take 0.1 seconds

(1 / 10)

does it make sense?

[dire veldt]

wait

yes

[fringe igloo]

also this is all called from Update

[dire veldt]

yeah i got that

last question

if i had used a constant, say 0.5 value in t

for Lerp()

does that mean all I would get is just the halfway point between 0 and 10 (if they there a and b in lerp)

and that's why t needs to change?

[fringe igloo]

yes, Mathf.Lerp(0f, 10f, 0.5f) returns 5f

check these

https://docs.unity3d.com/ScriptReference/Mathf.Lerp.html

oh ffs the bot keeps removing my message lol

anyway look at Mathf.MoveTowards and Mathf.Lerp in docs

[dire veldt]

lol

[fringe igloo]

(Vector3/Vector2 also have similiar functions)

[dire veldt]

i did try to look at them but it's my fault cause i did kinda skim them

so basically both of them are just another way of writing a function f(x) where x is t, and f returns the value x% towards b from a

[fringe igloo]

they are functions, with differing functionality

although they can be used for similiar use case

[dire veldt]

i see

[fringe igloo]

no, MoveTowards takes a distance instead of t

[dire veldt]

wait i'm lost again

OH

yeah that's what i wanted to ask

if i used something like Mathf.Smoothstep(0,1,t)

[fringe igloo]

Mathf.MoveTowards(0f, 10f, 3f) returns 3f

[dire veldt]

for the transitionTime that goes in Lerp

[fringe igloo]

Mathf.MoveTowards(3f, 10f, 3f) returns 6f

[dire veldt]

one last question

[fringe igloo]

yeah thats a good idea

[dire veldt]

does Time.deltaTime say more or less the same

because isn't it calculating the value time between current and last frame

[fringe igloo]

yes, but different frames can take different amount of time to process

ideally, your FPS would stay as stable as possible

[dire veldt]

okay with like a stable 60fps Time.deltaTime returns 1/60

[night bane]

Yes. Although it's different every frame due to many factors. And if you ignore that difference, it will accumulate and break something.

[dire veldt]

so how did u use it in MoveTowards?

because if it's more or less constant, wouldn't movetowards return the same value every time

[night bane]

Roughly. It will never be exactly 1/60 unless the stars align.

[dire veldt]

OH

u like

what's the word

REASSIGNED IT

OHHHHHH

so like

first time if u had x = mathf.movetowards(0,1,Time.dtime)

x = 0.1 for first frame
x = 0.2 for second

and so on right?

[fringe igloo]

nah you would do x = Mathf.MoveTowards(x, 1, Time.deltaTime)

notice x as first argument

[dire veldt]

oh yeah mb

that's what i meant

but for smoothstep, i can't do that, since t is a percent

so does that mean i need an inbuilt timer?

[fringe igloo]

you could change this:

  myFloat = Mathf.Lerp(minValue, maxValue, transition);

to this:

  myFloat = Mathf.Lerp(minValue, maxValue, Mathf.SmoothStep(0f, 1f, transition));

so that you sample with a smoothed t, not linear

otherwise, smoothstep doesnt really help here

[dire veldt]

oh even smarter

from now one Mathf.Movetowards is my bae

going to use it instead of timers

[fringe igloo]

now go explore 😎

this is all a bit easier to understand when you visualize it

[dire veldt]

yeah i tried to

by drawing lines on my pencil

it did not work out

okay here's my code

        float hAxis = Input.GetAxis("Horizontal");
        
        float transitionTarget = hAxis != 0 ? 1f : 0f;
        float targetSpeed = hAxis != 0 ? 10f : 0f;
        float transitionTime = 0;
        transitionTime = Mathf.MoveTowards(transitionTime,transitionTarget,Time.deltaTime);

        moveSpeed = Mathf.LerpUnclamped(moveSpeed, targetSpeed,Mathf.SmoothStep(0,1,transitionTime));
        return moveSpeed;

so moveSpeed does increase, but letting of the button doesn't seem to bring it back

any idea why?

[fringe igloo]

try Input.GetAxisRaw

instead of getaxis

reason: GetAxis has some smoothing in it, and may never reach 0

[dire veldt]

ah

i'm learning so much

and feeling dumber by the second

[fringe igloo]

alternatively you can replace hAxis != 0 with Mathf.Abs(hAxis) > 0.001f or something

anyway i got some stuff to do

[dire veldt]

thank you so much for helping

bye bye

[dire veldt]

okay i'm lost again

;-;

[fringe igloo]

paste code in a paste site or something

[dire veldt]

no the only thing i want to do now is

make it so that all this happens over the course of 3 seconds, instead of the default 1

[fringe igloo]

divide Time.deltaTime by the amount of seconds

[dire veldt]

yeah but then

[fringe igloo]

well what do you want to happen over 3 seconds?

the transition from 0 to 1?

[dire veldt]

no

the lerp

i can't multiply mathftowards right

wait

[fringe igloo]

can you stop typing vertically please?

[dire veldt]

oh yeah sorry my bad.

[fringe igloo]

the lerp is controlled by the transition though

so transition length determines lerp length

[dire veldt]

okay that makes sense.
if i'm correct, to should take 1/Time.deltaTime * some var frames to finish the transition correct

[fringe igloo]

you can have a float transitionDuration and then do
transitionTime = Mathf.MoveTowards(transitionTime, transitionTarget, Time.deltaTime / transitionDuration);

(i just added the / transitionDuration part to your code)

[dire veldt]

wait it's that simple?

i don't know whether to cry or rage or be happy

okay it didn't work

yes the movetowards functions takes x seconds to reach one, but the lerp function hits the max value much much faster

[fringe igloo]

would be cool if you show the code 🤷‍♂️

[dire veldt]

        // Transition value moves between 0..1 depending on key press state
        float transitionTarget = hAxis ? 1f : 0f;
        float targetSpeed = hAxis ? 10f : 0f; 
        transitionTime = Mathf.MoveTowards(transitionTime,transitionTarget,Time.deltaTime / accelerationTime);
        if (transitionTime > 0 && transitionTime < 0.99f) {
            timer += Time.deltaTime;   
        }
        // Update myFloat to be between min and max value, in range of transition
        moveSpeed = Mathf.LerpUnclamped(moveSpeed, targetSpeed,transitionTime);

        return moveSpeed;

[fringe igloo]

wait no.

this is wrong
moveSpeed = Mathf.LerpUnclamped(moveSpeed, targetSpeed,transitionTime);

and not like in my example

[dire veldt]

oh

[fringe igloo]

the idea was
moveSpeed = Mathf.LerpUnclamped(minMoveSpeed, maxMoveSpeed, transitionTime);

[dire veldt]

but then how can i do it so that if the player was already moving at a speed it accelerates/decceleatres

[fringe igloo]

thats nothing like what you originally described..

you wanted a switch that transitions from 0 to 1

or from x to y

[dire veldt]

i kinda wanted it to go from x to y, then back to x

depending on whether the key is pressed

[fringe igloo]

...?

thats what my code does

x is minSpeed and y is maxSpeed

[dire veldt]

yeah but letting go of the key doesn't bring it back

it keeps it there

[fringe igloo]

did you try this?

before saying it doesnt work

lol...
-asks for help
-gets solution
-implements solution wrong
-doesnt correct the solution
-blames solution

[dire veldt]

it goes from 2 to 10

then 0 to 2

okay that's a fair critique sorry for acting like the toxic noob

maybe i should just give up for now

work on another part

sorry for wasting your time

[fringe igloo]

@dire veldt just tested this and it does work

    float transitionTime;
    float moveSpeed;
    float minSpeed = 2f,
        maxSpeed = 10f,
        accelerationTime = 2f;
    void Test()
    {
        bool hAxis = Input.GetKey(KeyCode.A);

        float transitionTarget = hAxis ? 1f : 0f;
        transitionTime = Mathf.MoveTowards(transitionTime, transitionTarget, Time.deltaTime / accelerationTime);

        moveSpeed = Mathf.LerpUnclamped(minSpeed, maxSpeed, transitionTime);

        print("Speed: " + moveSpeed);
    }
    private void Update()
    {
        Test();
    }

[dire veldt]

:O

[fringe igloo]

it moves from 2 to 10 in 2 seconds, and back when you release

[dire veldt]

I currently have to do something but I'll try it later

If it does work thank you so much

[fringe igloo]

yeah I just wanted to check that nothing is wrong with what i gave you

but you should add just that to an object, then work your way up there, see where it breaks for you

[dire veldt]

Have u been doing gamdev for a long time,?

U seem rlly good

[fringe igloo]

Ive been dev for ages, Unity programming just a few years tho

not an expert but passionate hobbyist

[dire veldt]

Well I have to go now but again tysm

[dire veldt]

hey @fringe igloo

if ur not busy

I finally made my 100% own script for the walk cycle

the player moves at a constant rate towards the max speed, while the button is being pressed

i'm proud of it :)

    void RunAndWalk() {
        bool isMoving = hAxis != 0;
        float accelerationRate = (maxSpeed * Time.deltaTime)/timeToMaxSpeed;
        print(isMoving);
        if (isMoving) {
            playerSpeed = Mathf.MoveTowards(playerSpeed, maxSpeed * Mathf.Sign(hAxis), accelerationRate);
        } else if (playerSpeed != 0) {
            playerSpeed -= Mathf.MoveTowards(0,playerSpeed,accelerationRate);
        }