How can I trigger an event each time the rotation of my rigidbody2D is at a given value?

Question

I would like to trigger an event each time my rigidbody2D is at a particular value.

The event should only be triggered once for each given value per complete object revolution.

Initial attempts at achieving this have resulted in the following method which checks against an array of values, logging an event and incrementing an index when the value has been passed.

static readonly float[] angles = new float[] { 90f, 180f };  
int angleIndex = 0;

void CheckForTrigger()
{
    if (rigidbody2D.IsSleeping())
        return;

    var rotation = Mathf.Abs(rigidbody2D.rotation);

    if (rotation % 360f >= angles[angleIndex])        
    {        
        Debug.Log("Fire");

        angleIndex++;

        if (angleIndex== angles.Length)
            angleIndex= 0;
    }
}

This suffers from a couple of issues:

• Floating point inaccuracy means that values close to 360f will often be missed (e.g. 359f)
• Fire will be logged each frame between the last and first value (i.e. between 180f and 90f)

Does anyone have any advice for approaching this problem and improving the above method?

Answer 1

This is somewhat long and might not work well if they are rotating faster than the deadzone value, but then you can just increase the deadzone. I've commented the below code: //declare new array of the dataclass we made below

static AngleData[] angleDatas = new AngleData[] { new AngleData(90f), new AngleData(180f) };
int angleIndex = 0;
//the deadzone is how close it has to be to the target angle to fire, and how far it needs to be to 'reset itself'
float deadzone = 15f;
void CheckForTrigger()
{
    if (rigidbody2D.IsSleeping())
        return;

    var rotation = Mathf.Abs(rigidbody2D.rotation) % 360f;
    //we get the current AngleData
    AngleData currentAngle = angleDatas[angleIndex];
    //find the absolute difference from the target to the current rotation
    float difference = Mathf.Abs(rotation - currentAngle.angle);
    //if we haven't 'used up' this angle for this revolution
    if (currentAngle.available)
    {
        //if it's within the deadzone
        if (difference < deadzone)
        {
            Debug.Log("Fire:" + currentAngle.angle);
            currentAngle.available = false;
        }
    }
    else
    {
        //if it's outside the deadzone
        if (difference > deadzone)
        {
            currentAngle.available = true;
            //move on to next angle in list
            angleIndex = (angleIndex + 1) % angleDatas.Length;
        }
    }
}
public class AngleData
{
    public float angle;
    public bool available = true;
    //could have an event declared here if you want specific event methods to be fired for every different angle
    public AngleData(float angle) { this.angle = angle; }
}

Let me know if you have any questions or if it doesn't work as intended.