Easier way to calculate an adjusted proportion?

Unity Engine
,
1

Sorry if this has been answered before, but I have no clue what to actually call this, so all I have to go off is a description.

If I input a float Na that exists within range A, I want to output float Nb that is the same proportion within range B.

Say I have a float A with range (2,4).
Then I have float B with range (15,23).
If I input 3 (halfway between 2 and 4), it should output 19 (halfway between 15 and 23).

Here’s what I’ve written for doing the calculations:

float AdjustedProportion(float input)
    {
        //Convert to percent of first range
        float percent = (maxA - input) / (maxA - minA);

        //Convert back to number within second range
        return (maxB - (percent * (maxB - minB)));
    }

This works fine, but I was wondering if there is a better way to write this or if Unity has a built in Mathf function specifically for this.

2

You will find many posts if you search for converting values from one range to another, such as:
https://stackoverflow.com/questions/929103/convert-a-number-range-to-another-range-maintaining-ratio

You may find a few slightly shorter versions or tips on handling special cases there.
I dont think unity has a Mathf function for this. Might be wrong. But if what you have works, why change it?

3

Here’s a thread on that: I feel like I'm forced into using InverseLerp whenever I use Lerp.

The first post is from someone using inverselerp (to get the percent – your first line) followed by lerp (your second line). Then there are several people playing with custom rescale function (which is just what you write, as a function). Basically, the thread beats to death that you can make it look different, but there’s no obvious better way.

4

Your code is great!

My only quibble is that you’re doing everything with an inverted percent.

The math works out obviously, but to me a percent should be 0.0 at min and 1.0 at max

Yours is exactly the opposite. If you doubt me, print out the value of percent and see.

Personally, I would write it as:

    float AdjustedProportion(float input)
    {
        //Convert to percent of first range
        float percent = (input - minA) / (maxA - minA);

        //Convert back to number within second range
        return minB + percent * (maxB - minB);
    }

That way if you ever have to debug it the numbers aren’t 1.0f - percent, they’re “just” percent.

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