Physics time on iMac vs iOS device

Target Platforms Mobile
1

Probably a very simple solution to this, but posting this now as I look for it:

Spend time converting my little 2D game to using rigidbodies/colliders for everything. Spent time getting all the movement impulses to feel right on the pc.

When I ran it on the iPhone everything moved at quarter speed, or something.

I’m moving the character left/right via code like this:

if (transform.position.x > leftWall) rigidbody.AddForce(-375,0,0);

Changing the code to use our old buddy deltaTime worked, but the code looks like this (to get similar results):

if (transform.position.x > leftWall) rigidbody.AddForce(-65000 * Time.deltaTime,0,0);

It worked on the iPhone but seems silly to use numbers like that.

Thoughts?

2
  1. don’t use deltatime
  2. put all physics in fixedupdate, not update (see docs, it clarifies this).
3

Thanks. I just changed Update() to FixedUpdate() and I assume that’s ok? The Update loop was maybe 100 lines long but had 2-3 lines dealing with a rigidbody.

4

update is called every frame
fixed update is called every tenth of a second i think. (not sure on the interval, but i know its called based on time)

5

FixedUpdate is looped as often as you want it to be, and unity will render after an Update()

Ideally just physics and maybe sound if its spawned off rigid bodies.

6

The physics timestep is set in your Edit → Project Settings → Time → Fixed Timestep

Performing actions on physics objects (rigidbody, etc) outside of a FixedUpdate will cause physics sync issues (and thus things behave bizarre) :slight_smile: