Kinematic rigidbodies no longer holding velocity property?

An asset I use relies on setting and then reading the velocity property of kinematic rigidbodies. Obviously setting the velocity of a kinematic rb should have no effect on its movement, but this value was used in later calculations to manually translate attached objects.

Now it seems, as of the latest 2022.1 beta at least, that this no longer works. Directly setting the velocity (or angularVelocity) of a kinematic rb does nothing. It isn't stored. You can try this by manually setting the velocity of a kinematic rb to some non-zero value, then logging the velocity afterwards. No matter what you set it to it will always be 0. This is not the behavior of previous unity versions; previously you could set the velocity of a kinematic rb and it would store that value until the next physics tick.

Here's a test script illustrating the issue:

Code (CSharp):

1. using UnityEngine;
2.  
3. /// <summary>
4. /// Attach this to a kinematic rigidbody
5. /// </summary>
6. public class VelocityExample : MonoBehaviour
7. {
8.     void Start()
9.     {
10.         Rigidbody rb = GetComponent<Rigidbody>();
11.         Vector3 setVelocity = new Vector3(1, 2, 3);
12.         rb.velocity = setVelocity;
13.        
14.         // On 2020.3.18f1 this output is equal to setVelocity; on 2022.1.0b3.2528 this output is always (0.00, 0.00, 0.00)
15.         Debug.Log(rb.velocity);
16.     }
17. }

My question is, was this an intentional change or is this a bug?

 

Late reply but if we set a RB to kinematic, will it set the linear and angular velocities to zero ? Because if not when we disable kinematic it will continue on with the forces it had before being set to kinematic which is a problem. I currently set linear and angular velocities to zero when setting kinematic on, so that when i set the kinematic off the RB will not suddenly move away from the drop point. But now this method doesn't work so now i am not sure how to reset the data...

 

I'm using Photon Fusion and Unity 2022.1 and on my client test instance I'm getting spammed in the console every simulation frame:

Setting linear velocity of a kinematic body is not supported.
Setting angular velocity of a kinematic body is not supported.​

This didn't happen in older versions of Unity and is causing significant in-editor performance degradation during testing. Are there plans to fix this or a way to disable this warning?

 

Also having this issue and would love to know if there will be a fix any time soon.

 

this log is really annoying and we toggle kinematic on and off all over the place
please just make it ignore the velocity if kinematic

 

I don't understand why it would ignore the velocity? This has been working like forever. No need to change the behavior and no need to set a warning. This breaks things for unity assets.

Setting Rigibody velocity DOES work for kinematic rigidbody and it had always worked before. Why is this being removed? This warning should be removed.

 

Just noticed this whilst testing my multiplayer in 2022 LTS. I switch objects between kinematic and non-kinematic constantly. They will be in different states on different machines.

It was used as a data container but I also expected set values to be used as the initial values when changing to non-kinematic. Now I have to figure out the extent of the issues this presents.

 

I ran into the same problem today after installing Unity again after a hiatus and going back to old projects. For some reason the default(?) third person controller gives an error whenever I jump, the same error comes from some moving objects I spawn having velocity.

Here's some of the code that seems to be the problem.

Code (CSharp):

1. public void OnAnimatorMove()
2.         {
3.             // we implement this function to override the default root motion.
4.             // this allows us to modify the positional speed before it's applied.
5.             if (m_IsGrounded && Time.deltaTime > 0)
6.             {
7.                 Vector3 v = (m_Animator.deltaPosition * m_MoveSpeedMultiplier) / Time.deltaTime;
8.  
9.              
10.  
11.                 // we preserve the existing y part of the current velocity.
12.                 v.y = m_Rigidbody.velocity.y;
13.                 m_Rigidbody.velocity = v;
14.             }
15.         }

How would I change this out to work without errors?

 

@PVisser - I am trying to do the exact same thing. To get rid of the error you would do something like this:
```
public void OnAnimatorMove()
{
if (m_IsGrounded && Time.deltaTime > 0)
{

Vector3 v = (m_Animator.deltaPosition * m_MoveSpeedMultiplier) / Time.deltaTime;​

// we preserve the existing y part of the current velocity.
v.y = m_Rigidbody.velocity.y;
// m_Rigidbody.velocity = v; <--- OLD
m_Rigidbody.MovePosition(m_Rigidbody.position + v); <--- NEW
}​

}
```
This did rapidly increase the speed of the character though

 

having the same problem with the topdown engine asset... how can i solve that for evrything at once? ther's too many of them in old projects

 

In Visual Studio you can do search and replace (CTRL+H), though review each one rather than doing it in bulk because it could be a bit dangerous. You can also look up all references with shift+F12, which should give you a list of where you're setting that property. And if the projects are sufficiently old, just ignore it

 

We also relied on direct setting of velocity on 3D Rigidbodies and believe this should not be a warning or error. Kinematic means "without force" not "without velocity" as Unity uses velocity even for kinematic objects to integrate different positions for FixedUpdate/Update based on interpolation setting. The workaround of setting it internally via MovePosition doesn't produce the same results, as reported above and in our attempt. That direct setting of velocity was disallowed because it was technically undefined PhysX behavior is weak. It's important behavior for a number of games so Unity should find a way to keep it working, even if that means doing so outside of PhysX.