while (Input.mouseScrollDelta.y != 0) crashes unity

I have the following code in update:

Code (CSharp):

1. while (Input.mouseScrollDelta.y != 0)
2.         {
3.             Debug.Log(Input.mouseScrollDelta);
4.         }

I also get a crash when I use Input.GetAxis("Mouse ScrollWheel")

I want to use the while loop to increment/decrement a variable while the scroll wheel is being turned. The Debug.Log is just there to check the sort of values I get.

When I use an IF statement unity doesn't crash so I'm wondering why using a WHILE statement crashes Unity. I'm new to C# and Unity so apologies if the answer is obvious.

 

It doesn't crash, it freezes. It's an infinite loop. Unity only ever updates input data (or anything, really) between frames, and as long as your code is running, it won't be between frames. So, Input.mouseScrollDelta will never change, and it'll just loop forever.

 

So when I turn the scroll wheel Unity executes the while loop and tries to print Input.mouseScrollDelta an infinite amount of times in a single frame, but since it can't print it an infinite number of times it can't exit the while loop. Am I right in saying that?

 

Yep, that's it.

Even if there were nothing in the loop, it'd still get stuck, just evaluating Input.mouseScrollDelta.y != 0 over and over and over.

 

I understand now. Thank you StarManta for the help.

 

There's another factor here that can create infinite loops, too. Comparing two floats (Input.mouseScrollDelta.y and 0) for equality. Because of floating point inaccuracy, directly comparing two floats for equality rarely results in true.
https://en.wikipedia.org/wiki/Floating_point_error_mitigation

 

While a good general rule, that wouldn't be a factor here. Floating point inaccuracy only really comes up when math is applied to the float being compared. If you set a float explicitly to 0.0, it will reliably be compared to 0.0 in the future; and when Input.mouseScrollDelta's value is being determined, it almost certainly has something like:

Code (csharp):

1. if (scroll wheel isn't being moved) {
2. return 0f;
3. }

There's no math being done there, so in this case, comparing the result to 0f should be reliable.

(That is the exception rather than the rule, of course; in most cases this advice is correct.)

 

Then is it better for me in the future to compare a float to how near it is to 0 and set a variable to decide how sensitive I want it to be rather than compare to 0 whenever I can? So long as there is no math involved as StarManta says?

 

Yeah, Mathf.Approximately exists for this purpose. And for the sake of clarity, it wouldn't hurt to use it even in cases where == would work, it's just not necessary in those cases.

 

Thank you once again to the both of you for the insight