Havok, how to apply torque

Questions
1

Is there a way with Havok to apply torque ?

There is body.applyForce for applying a force affecting position, but how do I do the same for rotation?

Looking for something like NVIDIA(R) PhysX(R) SDK 3.4 API Reference: PxRigidBody Class Reference or Unity - Scripting API: Rigidbody.AddTorque

I know there is body.setAngularVelocity but that seems to introduce non interpolated behavior and weird twitching, so guessing this is not the optimal way.

2

Hello! What kind of twitching are you seeing? Can you share a playground?

3

What I’m seeing is “twitching” with a follow camera targeting my player, when making the players physicsbody turn. Will try isolating this in a playground.

Wondering how the Havok / render update relates and if there is any interpolation on the render side, e.g. similar to Unity: Unity - Scripting API: Rigidbody.interpolation

4

Looks like the “twitching” is actually coming from the FollowCamera. Using another simple TargetCamera just parented to the PhysicsBody looks much more smooth.

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5

Anyone here figured out how to do that? It actually don’t have a applyTorque function.

6

@eoin is this something we can add?

7

Oh, I’m surprised the plugin doesn’t have an applyAngularImpulse - definitely something we should add. In the meantime, something like this should do the trick:

    var body = ...;
    var torqueWorld = ...;

    var massProps = body.getMassProperties();
    var worldFromInertia = massProps.inertiaOrientation.multiply(body.transformNode.absoluteRotationQuaternion);
    var inertiaFromWorld = worldFromInertia.conjugate();
    var impLocal = torqueWorld.applyRotationQuaternion(inertiaFromWorld);
    var impWorld = impLocal.multiply(massProps.inertia).applyRotationQuaternion(worldFromInertia);
    var newAV = body.getAngularVelocity().add(impWorld.scale(scene.getPhysicsEngine().getTimeStep()));
    body.setAngularVelocity(newAV);
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9

Hi
Why doesn’t the Havok plugin have applyTorque/applyAngularImpulse functions? How do you implement them if simple things can’t be achieved without workarounds?
It won’t work to simply convert the angle into a vector and apply the impulse to that vector!

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12

Havok API has been updated with appropriate methods. I’ll update the physics API in the comign days.

13
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