How do I manually accelerate the rotation of a sphere in Unity 3D?

Question

I'm a little new to this so any help will be appreciated.

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Context: I'm creating a VR billiard/pool game and trying to get the physics as realistic as possible. I have a cue ball being hit with a cue across a surface with accurate friction values calculated from real world trials.

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Problem: The angular acceleration of the balls isn't realistic at all. Therefore the angular velocity is off (this is due to how Unity calculates physics of interaction as a point of contact rather than an area of contact and therefore friction calculation is done at one point causing it to rotate slower).

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Question: How can I manually set the angular acceleration to a value in code until the angular acceleration is greater than or equals to horizontal velocity, then the angular acceleration is set to 0? Thanks in advance.

Answer 1

Unity doesn't have an 'angular acceleration' field that you can set. You can set the angular velocity in code, as I showed in your previous question about this. If you need to accelerate or decelerate the angular velocity, you can do this manually in your code.

void Update() {
    if (rigidbody.angularVelocity.magnitude < desiredAngularVelocity) {
        //scales the acceleration each frame
        rigidbody.angularVelocity = rigidbody.angularVelocity * accelerationRate * Time.deltaTime;
    }
}

or if you want the angular velocity to change by a constant rate rather than scaling it, I think this will work (haven't tested it):

void Update() {
    if (rigidbody.angularVelocity.magnitude < desiredAngularVelocity) {
        float angularSpeed = rigidBody.angularVelocity.magnitude;
        angularSpeed += acceleration * Time.deltaTime;
        rigidbody.angularVelocity = rigidbody.angularVelocity.normalized * angularSpeed;
    }
}

Or if you want to use forces, try rigidbody.AddTorque()

rigidbody.AddTorque(transform.right * 10000);

This is more complicated because torque is 3D; you'll have to calculate the correct direction for the torque.

You may wish to review all of the functions available to Rigidbodies.