Simple (?) math problem - modulus difference

Unity Engine
1

I have two numbers, going from 0f → 1f.

They never go past 1f, or below 0f.

Now imagine I want to lerp one of these numbers to the other one, by using the “shortest distance”.

This would not work:

float firstNumber = time1 % 1f;
float secondNumber = time2 % 1f;

float result = Mathf.Lerp(firstNumber, secondNumber, t);

Because if firstNumber is .9f, and secondNumber .1f, the difference would be .8f. But the “smaller” difference would be .3f:

(.3f +.9f) % 1f = .2f

Now, the question is how to write a method that would always return this smaller difference. I feel so confused right now.

2

Mathf.Min?

1 Like
3

Sure, but how would you write a function that gets the .3f in the case above? I.e. how do you “unmodulus” something?

4

I am not sure I understand. You want to lerp between 2 values but by the sound of it you also want to support wrap around lerping I.E going over 1 goes back to 0?

Something like this:

float firstNumber = time1 % 1f;
float secondNumber = time2 % 1f;

float diff = secondNumber - firstNumber;
float diffWrapAround = (1 - firstNumber) + secondNumber;

if(diffWrapAround < diff)
{
    // Wrap lerp
    float result = Mathf.Lerp(firstNumber, secondNumber + 1, t);
    if(result>1)
        result-=1;
}
else
{
    // normal lerp
    float result = Mathf.Lerp(firstNumber, secondNumber, t);
}

Just a quick hack, no guarantee it works :wink:

1 Like
5

Yes, exactly, sorry if I wasn’t clear on that. That’s why I have % 1f when setting the variables.

I’ll test your code and get back to you. Thanks!

6

Alternatively take the CLerp function from here and modify it for specifying your own values.
http://wiki.unity3d.com/index.php?title=Mathfx

1 Like
7

Thanks a lot!

So nice to see unity employees replying. :slight_smile: Keep it up!

1 Like