RigidBody -> 0 velocity -> still moving?

Hi,

id like to stop the movement of a rigid body affected by gravity.

Test1: set gravity to 0 (Physics.gravity.y = 0 or something like that)
Result: rigid body isnt moving

Test2: keep gravity. Set RigidBody.velocity to Vector3 (0,0,0) in onFixedUpdate.
Result: Rigid body is moving ever so slightly downwards.

My question is, how can i stop RB movement while keeping gravity settings intact?

 

Gravity is an acceleration. You might set the velocity to zero, but the acceleration moves it slightly on each physics step before you actually reset the velocity to zero again.

In addition to setting velocity to zero, you must cancel the action of the gravity in that rigidbody. You can do so like this:

Code (CSharp):

1.  
2. void FixedUpdate ()
3.    {
4.    GetComponent<Rigidbody>().AddForce(-Physics.gravity, ForceMode.Acceleration);
5.    }

EDIT: Note that this has the same exact effect as disabling "Use Gravity" in the Rigidbody component. There's no difference on using the above code or disabling gravity in the rigidbody.

 

Thank you for the reply! I cant test this atm, as i worked around the problem, but this will definitely help in the future!

 

Just curious why not just set the gravity off? It would be much more performance efficient.

 

@RavenOfCode can you turn off gravity for that specific RB? because other RBs are also using gravity..

 

I don't think there's a difference in performance here. All the gravity does is:

Code (CSharp):

1. AddForce(Physics.gravity, ForceMode.Acceleration);

Adding an exact opposite acceleration just cancels the one set by gravity. All forces/accelerations are combined (summed) and the resulting single force is applied to the rigidbody on the next physics update.

So disabling gravity is just a more convenient way (that's what the rigidbody.useGravity property is for), but not a significant performance improvement.

 

Yeah, just grab that particular rb and turn it off.

Code (CSharp):

1. GetComponent<Rigidbody>().UseGravity = false;

 

So that method actually exists.. Kappa. Thank You.