The linear damping of PxRigidBody

[SHiziw]

Hello NVIDIA Devs,

I have adjusted the damping of a PxRigidBody to 0.01 using the setLinearDamping method. Interestingly, I've observed that the maximum velocity induced by gravity remains constant, regardless of the mass of the object. However, according to Newton's second law:

$$mg - c\frac{dx}{dt} = m\frac{d^2x}{dt^2}$$

we can derive that the maximum velocity is given by:

$$v_{max} = \frac{m g}{c}$$

This suggests that the maximum velocity should indeed be related to the mass of the object. I'm puzzled as to why this isn't the case in my observations.

Do you have any thoughts on why this is happening?

Thanks!

[preist-nvidia]

Hi @SHiziw,

Linear damping does not apply a force proportional to velocity, but scales the (unconstrained, pre-integrated) velocities each time step with

max(0, 1 - linear_damping * dt)

see, for example, here: https://github.com/NVIDIA-Omniverse/PhysX/blob/main/physx/source/lowleveldynamics/src/DyBodyCoreIntegrator.h#L62

I agree that the documentation does not make this clear enough, I'll update it.
Philipp

[SHiziw]

Thank you the detailed answer!