How to convert lerp to cubic easing in?

Question

I need to convert the following code from using lerp to using cubic easing in, but I don't know what to do with the returned float value from the cubic easing in function, because I'm using Vector3 instead of floats. Can someone please give me a hint?

    if (Vector3.Distance(activeTween.Target.position, activeTween.EndPos) > 0.1f)
        {
            float fraction = (Time.time - activeTween.StartTime) / activeTween.Duration;
            activeTween.Target.position = Vector3.Lerp(activeTween.StartPos, activeTween.EndPos, fraction);
        }

JonasH · Answer 1 · 2021-09-17T07:03:04.080

2

You should probably just use it in place of your fraction in the Vector3.Lerp.

Lerp is just the linear interpolation of vectors, i.e. 0.3 means 30% from one and 70% from the other. If we want non linear interpolation we can just apply some arbitrary function to the input value. For example, that 0.3 may be transformed to 0.027, and that can then be used as the input to Lerp to get 2.7% / 97.3% blend instead.

edited Sep 17 '21 at 07:03

answered Sep 17 '21 at 06:16

JonasH

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thanks! I dont know easing is based on lerp... – Weeboo Sep 17 '21 at 06:49

score 1 · Accepted Answer · answered Sep 17 '21 at 06:37

You need a cubic function that is 0 at the start and 1 and the end. I would try something like:

public float EaseIn(float t)
{
    return t * t * t;
}

if (Vector3.Distance(activeTween.Target.position, activeTween.EndPos) > 0.1f)
{
    float fraction = (Time.time - activeTween.StartTime) / activeTween.Duration;

    activeTween.Target.position = Vector3.Lerp(activeTween.StartPos, activeTween.EndPos, EaseIn(fraction));
}

Assuming that fraction was already going from 0 to 1.

thanks! I thought lerp is totally different from easing, bluh — Weeboo, Sep 17 '21 at 06:47

How to convert lerp to cubic easing in?

2 Answers2