Rigidbody.inertiaTensorRotation

[Proigr]

Hello, I want to ask How does Rigidbody.inertiaTensorRotation work? How does it effect the behaviour of a Rigidbody? I want to predict the behaviour of AddForceAtPosition(), how do I use this?

[Edy]

This thread contains tons of useful information on inertiaTensor and inertiaTensorRotation:

Inertia tensor in Matrix Form from InertiaTensor and InertiaTensorRotation

Hello, Inertia tensor is normally defined as a 3x3 Matrix [6141420--670203--upload_2020-7-28_14-2-20.png] Unity and Physx give something equivalent, an IntertiaTensor, and an InertiaTensorRotation. I think they do it like this because it is cheaper (3+4 = 7 values) against (3x3=9 values). My question is, having an InertiaTensor and an InertiaTensorRotation, how can I calculate the 3x3 Inertia Tensor? I reckon this should be quite straightforward but I can't get the maths right I am tem…

[lightbug14]

Here’s a little example that shows how this can affect rotation.
Let’s say you allow only y rotation (yaw):
inertiaTensor = <inf, 1, inf>

Then, you set the tensor rotation as:
Quaternion.Euler(90,0,0)

This will rotate the tensor 90 degrees along the x axis. So, the “rotated tensor” will be:
rotatedInertiaTensor = <inf, Inf, 1>

Now only z rotation (roll) is allowed.

[Proigr]

Thank you!