Question by Jamboozler · Oct 10, 2020 at 05:19 PM · rotation 3d ai

Efficient Rotation with Different Rotation Rates on Each Axis

I am currently developing the AI behavior for a 3D space simulation game. The first behavior I am attempting to implement is for an NPC to rotate towards a target.

Note: Each axis the ship can rotate on (pitch, yaw, and roll) has a set rotation rate. As such, I am not sure if it is possible to implement this using Quaternion.RotateTowards(). I am currently rotating incrementally to face the target as shown in the code below:

 private void LookAtTarget()
     {
         // Find the Target Rotation to Look At
         Vector3 targetRotation = Quaternion.LookRotation(target.transform.position - this.transform.position, Vector3.up).eulerAngles;
         Vector3 currentRotation = this.transform.rotation.eulerAngles;
 
         Vector3 rotationIncrement = Vector3.zero; // Our Vector3 to Store the Rotational Increment
 
         // Get Pitch Increment Amount
         GetRotationIncrementOnAxis(currentRotation.x, targetRotation.x, pitchRate, ref rotationIncrement.x);
         // Get Yaw Increment Amount
         GetRotationIncrementOnAxis(currentRotation.y, targetRotation.y, yawRate, ref rotationIncrement.y);
         // Get Roll Increment Amount
         GetRotationIncrementOnAxis(currentRotation.z, targetRotation.z, rollRate, ref rotationIncrement.z);
 
         // Apply Rotation Increment to our Current Rotation
         this.transform.rotation = Quaternion.Euler(currentRotation + rotationIncrement);
     }
 
     /**
      * Helper method for LookAtTarget() for getting the rotation increment on a specific axis
      */
     private void GetRotationIncrementOnAxis(float currentRotation, float targetRotation, float rate, ref float rotationIncrement)
     {
 
         // Determine the Direction to Rotate
         float sign = Mathf.Sign(targetRotation - currentRotation) * -Mathf.Sign(Mathf.Abs(targetRotation - currentRotation) - 180);
 
         // Apply Rotation Rate and Frame Time
         rotationIncrement = sign * rate * frameTime;
 
         // Adjust Rotation Increment if it is Greater than the Difference between our Target and Current Rotations
         if (Mathf.Abs(targetRotation - currentRotation) < Mathf.Abs(rotationIncrement))
         {
             rotationIncrement = targetRotation - currentRotation;
         }
     }

This code achieves the desired behavior. However, it proves to be inefficient when the rotation rate of a specific axis is very low. For instance, one ship has the given rotation rates below:

Pitch: 60
Roll: 45
Yaw: 20

In this case, it would be much more effective to pitch and roll to face the target. How could I find the fasted way to rotate towards the target when each axis has a different rotation rate?

Thank you in advance for any advice or resources you can provide!

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