How to use Physics.autoSyncTransforms in unity?

[listen941226]

I am a beginner developer. I have been studying the unity physics system recently. Because I have to do a lot of optimization about the physical system, I paid attention to these two apis, but I don’t know what the specifics are and how to use them. Thank you?

[system]

Perhaps I am not familiar with your specific use case but how in the world do you expect Unity’s physics feature to be unable to handle your simulation/game with the Job System and ECS already in place?

[listen941226]

Perhaps I am not familiar with your specific use case but how in the world do you expect Unity’s physics feature to be unable to handle your simulation/game with the Job System and ECS already in place?

I added a collider to an object but didn’t add a rigidbody. Now I want to move this object through transform, will it cause performance consumption? So I need to study Physics.autoSyncTransforms

[system]

Been there, done that, don’t do it. Add a rigidbody and things will be much easier. Moving transforms is not only inefficient and bad practice, but you will have to implement your own physics layer (which includes a headache I mean collision handling). Even if you have a collider it will not affect the object in the way I think you think it will.

[Joe-Censored]

Objects with a collider that do not have a rigidbody should not be moved. You will get performance issues, unreliable physics interactions, and unexpected results. See the manual:

@Unity Manual

Static Collider

This is a GameObject that has a Collider but no Rigidbody. Static colliders are used for level geometry which always stays at the same place and never moves around. Incoming rigidbody objects will collide with the static collider but will not move it.

The physics engine assumes that static colliders never move or change and can make useful optimizations based on this assumption. Consequently, static colliders should not be disabled/enabled, moved or scaled during gameplay. If you do change a static collider then this will result in extra internal recomputation by the physics engine which causes a major drop in performance. Worse still, the changes can sometimes leave the collider in an undefined state that produces erroneous physics calculations. For example a raycast against an altered Static Collider could fail to detect it, or detect it at a random position in space. Furthermore, Rigidbodies that are hit by a moving static collider will not necessarily be “awoken” and the static collider will not apply any friction. For these reasons, only colliders that are Rigidbodies should be altered. If you want a collider object that is not affected by incoming rigidbodies but can still be moved from a script then you should attach a Kinematic Rigidbody component to it rather than no Rigidbody at all.

Unity - Manual: Introduction to collision

[listen941226]

Been there, done that, don’t do it. Add a rigidbody and things will be much easier. Moving transforms is not only inefficient and bad practice, but you will have to implement your own physics layer (which includes a headache I mean collision handling). Even if you have a collider it will not affect the object in the way I think you think it will.

Thank you very much, you are right, but because there are a lot of GameObjects, if you add Rigidbody, will it consume performance? I am very confused now.

[listen941226]

@Joe-Censored

Objects with a collider that do not have a rigidbody should not be moved. You will get performance issues, unreliable physics interactions, and unexpected results. See the manual:

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

Thank you very much, I am stupid, but because I have a lot of GameObjects, if I add a rigid experience, it will not cause performance consumption? Thank you very much for your answer.

[Joe-Censored]

@listen941226

Thank you very much, I am stupid, but because I have a lot of GameObjects, if I add a rigid experience, it will not cause performance consumption? Thank you very much for your answer.

Well any component you add will have some performance impact, as it is more code that will need to run. Unity has done their best to limit the performance impact of individual rigidbodies of course. I’d suggest profiling your game before, then add rigidbodies and check the profiler again to see if the hit is significant. If you’re just talking about a handful of objects you will probably not see much if any.

[Edy]

@Joe-Censored

Objects with a collider that do not have a rigidbody should not be moved. You will get performance issues, unreliable physics interactions, and unexpected results. See the manual:
https://docs.unity3d.com/Manual/CollidersOverview.html

The information in the manual is outdated. Starting around Unity 5 (PhysX 3.3) moving static colliders causes no penalties anymore. If you just need colliders without Rigidbody, then there’s no need to use it.