Question on OnTriggerStay2D and use or not use of time.fixeddeltaTime

So i making a 2D spaceship game using the built in physics engine Rigidbody2D and i want my ship to boost. when hitting an area. it works but some questions on Unity - Scripting API: MonoBehaviour.OnTriggerStay2D(Collider2D) (unity3d.com)

It has the following code.

Code (CSharp):

1. void OnTriggerStay2D(Collider2D other)
2.     {
3.         other.attachedRigidbody.AddForce(-0.1F * other.attachedRigidbody.velocity);
4.     }

Shouldn't have a Time.fixedDeltaTime in it to be framerate independent? wouldn't it give inconsistent results on the speed of the computer? Shouldn't it be the following

Code (CSharp):

1. void OnTriggerStay2D(Collider2D other)
2.     {
3.         other.attachedRigidbody.AddForce(-0.1F * other.attachedRigidbody.velocity *Time.fixedDeltaTime);
4.     }

Also looking at the unity runtime execution order. onTriggerXXX happen in the physics cycle. I'm just curious. why it is written that way and if there are issues or not

 

No. OnTriggerXXX functions run as part of the physics update. This means they are simulated at a fixed rate, just like FixedUpdate().

Besides, Time.fixedDeltaTime is a constant value (doesn't change frame to frame like Time.deltaTime), and therefore would not be suitable for doing variable-framerate adjustment.

 

The general rules for using delta or not is this:

- if YOU are doing the movement calculation, then YOU should multiply by the delta time.

- if you expect the PHYSICS engine to move stuff, then do NOT multiply by delta time

The first would apply in the case of changing positions in code and calling .MovePosition()

The second would apply to AddForce, AddTorque, velocities, etc.

 

Whoa thanks i was doing it wrong all along.