Question Comparing a clamped float value with an integer (max value)...

Good day everyone!

I have code:

float a,b;

float lerp = a/b;

lerp = Mathf.Clamp(lerp, 0, 1);

Which of these comparisons will work correctly?
a) if (lerp == 1)
OR
b) if (Mathf.Approximately(lerp, 1))
?

At the moment I'm using a) and it works OK, but I learned that floating numbers need to be compared using Mathf.Approximately.
In my case I'm comparing a float to an integer and I don't know how that works for c#. Maybe the integer is converted to float when compared?

 

I don't recommend ever comparing float for equality, even if you feed constants in.

Mathf.Approximately is great, but

if (lerp >= 1)

is better.

Or do your own notion of how close it has to be:

Code (csharp):

1. if (Mathf.Abs( lerp - 1) < 0.1f) ...

But remember if your terms move fast enough those will fail too.

That's why I always like

>=

ALSO, just as a note, *.Lerp() will actually clamp the third term already for you.

ALSO... here's a pattern I really like:

Code (csharp):

1. float duration = 2.3f;
2.  
3. for (float t = 0; t < duration; t += Time.deltaTime)
4. {
5.   float fraction = t / duration;
6.  
7. /// do my lerp here using fraction as the third argument
8.  
9.    yield return null;
10. }

BUT! The above might never actually fire on 1.0 so you have to adjust after the loop exits.

This is a modified form that WILL perform the final 1.0f lerp, but it can be baffling:

Code (csharp):

1. float duration = 2.3f;
2.  
3. for (float t = 0; true; t += Time.deltaTime)
4. {
5.   float fraction = t / duration;
6.  
7. /// do my lerp here using fraction as the third argument
8.  
9.    yield return null;
10.  
11.    if (fraction >= 1) break;
12. }

Of course, if you're just lerping stuff around, perhaps you should be using DOTween or LeanTween or some other tweener. No sense reinventing the wheel!

 

Thanks!

I have this code in my project, and it always stops at the right time. And I'm curious why I never got the error. Am I lucky, or is the probability too low?

Code (CSharp):

1. float duration = 1.4f;
2. while (true)
3. {
4.     float lerp = time/duration;
5.     lerp = Mathf.Clamp(lerp, 0, 1);
6.     if (lerp == 1) break; // always works;
7.     time += Time.deltaTime;
8.     yield return null;
9. }

 

In theory line 5 should clamp it at the constant 1

This allows your line 6 to succeed, as it compares to a constant.

However, should you in the future change that value like to 1.1 ... it might stop working.

Now you're very unlikely to... but stuff like that happens all the time.

Why do you think software (in general) in this world is so @$$##@$@#$ ridiculously buggy?

Here's some more reading, including a cool visualizer at the bottom.

Floating (float) point imprecision:

Never test floating point (float) quantities for equality / inequality. Here's why:

https://starmanta.gitbooks.io/unitytipsredux/content/floating-point.html

https://forum.unity.com/threads/debug-log-2000-0f-000-1f-is-200.1153397/#post-7399994

https://forum.unity.com/threads/why-doesnt-this-code-work.1120498/#post-7208431

"Think of [floating point] as JPEG of numbers." - orionsyndrome on the Unity3D Forums

Literal float / double issues:

https://forum.unity.com/threads/err...annot-be-implicitly-con.1093000/#post-7038139

And thanks to halley for this handy little visual floating point converter:

https://www.h-schmidt.net/FloatConverter/IEEE754.html

 

Also, you should understand that you are not actually comparing a float to an int. The comparison operators only work on two values of the same type. So, even if you write an int literal, or one of the variables is a float, the comparison is always taking place between a float and a float, or an int and an int. I'm not checking your code specifically in my IDE right now, but if you hover over the comparison operator in Visual Studio with your mouse it will tell you which types are being compared. The types you present are implicitly converted to those types before the comparison. So, you're not really comparing a float to an int. Make sure you understand that and inspect your comparison operator to know which values are being converted to which types for comparison.