How to lerp with a changing "from" value?

Question

It's possible I'm not even using t$$anonymous$$s right but basically I'm making a hunger system and I'm calling t$$anonymous$$s in fixed update:

    public void Starve()
    {
         if(CurrentHunger > 0)
         {
           CurrentHunger = Mathf.Lerp(CurrentHunger, 0, HungerRate * Time.deltaTime);
         }
 
     }

In t$$anonymous$$s example, CurrentHunger starts as 100. Hunger rate is 15. My time.deltaTime is 0.02. With t$$anonymous$$s use of lerp, basically, my from value is always changing.

So:

1 second it is 70
2 seconds it is 49
3 seconds it is 34.3
4 seconds its is 24.01

See? It's not decrementing linearly. Am I even using lerp right? And what do I need to do to fix t$$anonymous$$s?

Answer 1

Best Answer

Answer by Bunny83 · Jul 21, 2016 at 11:52 PM

Lerp won't work in that case. Both values need to be constant.

Instead of Lerp you might want to use Mathf.MoveTowards w$$anonymous$$ch does exactly what you want.

Lerp is implemented like t$$anonymous$$s:

 public static float Lerp(float a, float b, float t)
 {
     return a + (b - a) * Mathf.Clamp01(t);
 }

w$$anonymous$$le MoveTowards is implemented like t$$anonymous$$s:

 public static float MoveTowards(float current, float target, float maxDelta)
 {
     if (Mathf.Abs(target - current) <= maxDelta)
     {
         return target;
     }
     return current + Mathf.Sign(target - current) * maxDelta;
 }

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nerdares · Jul 22, 2016 at 12:22 AM 0

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I also think I have found a solution:

I already had a value called MaxHunger which is 100;

I made a new value called currentHungerDelay. This will help update the third parameter in the lerp section as I need to keep the values of the first two parameters constant, like you said.

Therefore, I set currenthunger equal to the new lerp value and I made sure current hunger was not part of the parameters in there. Here's the code

 public void Starve()
     {
         currentHungerDelay += Time.deltaTime;
         if (currentHungerDelay >= HungerRate)
             currentHungerDelay = HungerRate; 
 
 
         float t = currentHungerDelay / HungerRate;
 
         CurrentHunger = Mathf.Lerp(MaxHunger, 0, t);
         
     }

How to lerp with a changing "from" value?

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