Mapping or scaling values to a new range

Hi all, searched around a bit and didn't find anything, but certainly could have missed it.

Wondering if there's a built-in function which can take a value and scale/map it to a different range, where you can set the input and output ranges. For example:

inputLow = 1, inputHigh = 5
outputLow = 10, outputHigh = 100

if you send in 1, you'll get 10; if you send in 3, you'll get 60; if you send in 5, you'll get 100.

So it's an offset-plus-scale, all in one. I suppose you can just roll your own each time, but wondering if it exists already as a function (and maybe with exponential scaling?)

I know other languages have this, just wondering if it was something obvious I missed...maybe some trick with Lerp?

Thanks!

 

You can use a Lerp/InverseLerp combo:

Code (csharp):

1. var result = Mathf.Lerp (10, 100, Mathf.InverseLerp (1, 5, 3));

Or a function I wrote to do this a while ago, which has the advantage of a little better performance in addition to somewhat simpler syntax:

Code (csharp):

1. var result = SuperLerp (10, 100, 1, 5, 3);
2.  
3. function SuperLerp (from : float, to : float, from2 : float, to2 : float, value : float) {
4.     if (value <= from2)
5.         return from;
6.     else if (value >= to2)
7.         return to;
8.     return (to - from) * ((value - from2) / (to2 - from2)) + from;
9. }

--Eric

 

Ah, that's it! I had that formula around somewhere (from Max/MSP "scale" object) but couldn't remember it exactly. Same as processing's "map" function. Might be nice to have it as a built-in function in Unity like "Mathf.Map" or something.

Interesting about the Lerp/InverseLerp combo idea too, I'll have to experiment with that.

Thanks for the info!

 

These solutions didn't work for me after translating them to C#
I ported a solution I found on stackoverflow. Maybe this is useful for somebody else

Code (csharp):

1. public float scale(float OldMin, float OldMax, float NewMin, float NewMax, float OldValue){
2.  
3.     float OldRange = (OldMax - OldMin);
4.     float NewRange = (NewMax - NewMin);
5.     float NewValue = (((OldValue - OldMin) * NewRange) / OldRange) + NewMin;
6.  
7.     return(NewValue);
8. }

Usage:

Code (csharp):

1. float scaleMe = 0.5F;
2. float scaled = scale(0F, 1F, 10F, 20F, scaleMe);

Returns: 15

 

Thanks Eric5h5, I needed that as well. I rewrote the function in C# and called it Map for simplicity (hopefully not affecting any reserved names, though it seems to work fine).

Code (CSharp):

1. public float Map(float from, float to, float from2, float to2, float value){
2.         if(value <= from2){
3.             return from;
4.         }else if(value >= to2){
5.             return to;
6.         }else{
7.             return (to - from) * ((value - from2) / (to2 - from2)) + from;
8.         }
9.     }

Code (CSharp):

1. Debug.Log(Map(0,10,0,1024,500));

 

Hey @EID,
Somehow the code above didn't work for me, but the actual Arduino map function works well with minor modification (changing long datatype to double) - at least in my application.

Code (csharp):

1.  
2.     public double Map(double x, double in_min, double in_max, double out_min, double out_max)
3.     {
4.         return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
5.     }
6.  

 

Since its back up top, animation curves are another way of mapping values between ranges with a bit more flexibility.

 

'twas the same for me, and Arduino / C++ is probably the function most people will recognize
But if I may add to it:

Code (csharp):

1.  
2.     using System;
3.  
4.     public double Map(double x, double in_min, double in_max, double out_min, double out_max, bool clamp = false)
5.     {
6.         if (clamp) x = Math.Max(in_min, Math.Min(x, in_max));
7.         return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
8.     }
9.  

Set clamp to true and you'll be ensured your value is clamped in between in_min and in_max. A neat little parameter for a neat little function.

 

Thanks it is working great =)

 

I'm surprised there isn't a fit function as part of Mathf. Both "fit" and "fit01."

 

fit01 would be Mathf.InverseLerp

 

No, this topic is specifically not about InverseLerp. We all already know about that.

--Eric

 

But then what is fit01? I would expect "fit 20 to 0 and 1, based on 10 and 30". That would be

Mathf.InverseLerp(10, 30, 20); // = 0.5f