Question fixed update vs update

if i need to run a check very fast and often but didn't need it to happen every single frame, would it be more performance efficient to run it in fixed update or in update

 

FixedUpdate does not actually happen at a separate time than Update, it just runs right before every Update the amount of times for the Physics to catch up. I don't believe it would really be a performance hit either way, but I imagine if you didn't use any physics at all you could cut out those step calculations.

 

oh i thought fixed update happened a fixed amount every second. but yeah i agree it shouldn't be a performance hit either way

 

It's complicated.

Here is some timing diagram help:

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

Two good discussions on Update() vs FixedUpdate() timing:

https://jacksondunstan.com/articles/4824

https://johnaustin.io/articles/2019/fix-your-unity-timestep

 

It does.. RedPanda is just saying that... err.. hmm... He's just saying things! Don't ask questions!..

 

Under ideal conditions where the target device is able to keep up it will happen a fixed amount per second. It's just not guaranteed when it will happen during that second. If the target device can't keep up all of that gets thrown out the window and that's what the links @Kurt-Dekker gave touch on.

 

It doesn't happen at strictly fixed intervals. It plays catch up with Update using an accumulator. It's only there for the physics engine and not a way to have something happening at regular intervals.

A regular timer in Update will be more reliable.

 

Yup FixedUpdate doesn't really run at fixed intervals, just the end result looks like it does.

 

Best way to do this is create your own thread and timer upon/within it.

Anything else will suck time out of the precious main thread that just about everything in Unity relies upon.

 

oooh ok, these do explain it alot, i also just watched Jonas Tyrollers video on delta time which also explained alot, thx