Getting input in Update() and execute movement in FixedUpdate()

What happens if I get my input values in Update() and execute movement in FixedUpdate() depending on them? I heared I should do it this way - but imagine following scenario:

Code (CSharp):

1. void Update()
2. {
3.       jump = Input.GetButtonDown("Jump");
4. }
5.  
6. void FixedUpdate()
7. {
8.        if(jump == true)
9.        {
10.              jump();
11.        }
12. }

Frame 0: Player presses "jump" (Update)
Frame 0: jump = true (Update)
Frame 1: Player releases "jump" (Update)
Frame 1: jump = false (Update)
Frame 2: physic calculations start -> jump == false -> dont jump (FixedUpdate)

 

You need to have another variable that stores that your player wishes to jump and upon fixed update using that it would then be reset.

For instance:

Code (CSharp):

1.     void Update()
2.     {
3.           if(!jump && Input.GetButtonDown("Jump") jump = true;
4.     }
5.    
6.     void FixedUpdate()
7.     {
8.            if(jump)
9.            {
10.                  jump = false;
11.                  //apply jump
12.            }
13.     }
14.  

 

That is close to the correct approach. The only problems are:

- instead of assigning jump from GetButtonDown() every frame, do this:

Code (csharp):

1. if (Input.GetButtonDown("Jump")) jump = true;

There actually is a significant logical difference that I'll let you work out.

- in FixedUpdate() you want to also set

jump = false;

after you perform the actual

DoJump()

method. Otherwise you may still get double /triple jumps.

- as an aside, you are recycling the identifier

jump

but I know what you mean and that you are likely just typing casually in the forum.

Meanwhile, here is some timing diagram help:

https://docs.unity3d.com/Manual/ExecutionOrder.html

Which shows you why you don't want to assign every frame.

EDIT: @adehm nailed it right as I pressed submit! NICE!!

 

@Kurt-Dekker

Thanks. But how to react to the moveinput in update?

When i get the values in update() by

moveX = Input.GetAxis("Horizontal");
moveZ = Input.GetAxis("Vertical");

Is it still correct to do charactercontroller.move() with these parameters in FixedUpdate()? In this case i suggest there should be no set of "moved = true" or similar...?

 

Gathering continuous input (such as what is returned from

Input.GetAxis()

versus

Input.GetKeyDown()

) is less of a problem. You actually CAN do that in FixedUpdate().

HOWEVER, it is good practice to break apart all the phases of your game's main loop:

- Gather ALL the input, put it into variables

- Process the input out of those variables, as appropriate

The thinking behind this is that if you decide tomorrow "hey I want to support XBox Kinect for input!" then you have only one place to do the input gathering, because you have created a clear demarcation between "gather, process". It would just become "gather 1, gather 2, process"

 

Ok so there should be an Input Handler with

Code (CSharp):

1. if (Input.GetButtonDown("Jump")) jump = true;

in Update()

and a movement class with

Code (CSharp):

1.  
2. if (inputHandler.jump)
3. {
4. Jump();
5. inputHandler.jump = false;
6. }

in FixedUpdate()

?