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Fixed in 2022.1.X

Votes

3

Found in

2020.3

2020.3.20f1

2021.1

2021.2

2022.1

Issue ID

1375711

Regression

No

ArticulationBody.maxLinearVelocity doesn't limit velocity when forces are applied to the Articulation Body

Physics

-

How to reproduce:
1. Open the user's attached project
2. Open scene TestScene
3. Press the Play button and observe the Console

Expected result: the logged velocity of each Articulation Body is equal to the applied maximum velocity (1)
Actual result: each Articulation Body reaches the target position immediately before logging movement and the logged velocity is 0

Reproducible with: 2020.3.21f1, 2021.1.27f1, 2021.2.1f1, 2022.1.0a13
Could not test with: 2019.4.32f1 (The type or namespace name 'ArticulationBody' could not be found)

Notes: the Scene contains three test GameObjects, which apply either maxLinearVelocity, maxJointVelocity, or both

  1. Response avatar

    Resolution Note (fix version 2022.1):

    PhysX Actually limits the velocity, but it does so pre-solver, which means that after the physics simulation step, the velocity may exceed the maximum value.
    You can see this in effect if you used smaller values (Body damping/friction 0, Drive damping 1, Drive TargetVelocity 10 and a maxVelocity value of 0.5). The body will increase in speed until reaching 0.5, then it will go to around 0.68 and stay there. PhysX clamps the velocity to 0.5, then the solver increases it afterwards to 0.68.

    The intended use for this property is as a fail-safe for huge velocities (where the maxVelocity would be set to a really large value) to save from exploding simulations. To properly limit velocities it would be better to do so by limiting the forces that the Articulation Drive can apply using the Articulation Drive force limit property.

    The Documentation will be updated to reflect this functionality.

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