Making an enemy follow player (Unity)

Question

I'm working on coding enemy ai for a star fox-esqe shooter and I need the enemy to approach the player, stay a certain distance away and stay in front of them until destroyed. I can get the enemy to approach the player and I can get the enemy to stay a certain distance from the player but I'm not sure how to get the enemy to actually stay in front of the player. For a bit of extra information, the player makes a number of sharp turns and the like throughout the level. Also, as a stand in I tried simply causing the enemy to parent to the player within a certain radius but that causes clipping issues with buildings and the ground.

public class EnemyCar: MonoBehaviour
{
    public float safeDistance = 20f; // How close the enemy can get to the player


    // ...

    // Update is called once per frame
    void Update()
    {
        transform.LookAt(player.transform);

        Vector3 targertLocation = player.transform.position - transform.position;
        float distance = targertLocation.magnitude;

        // Decrease our speed as we get closer
        rb.AddRelativeForce(Vector3.forward * Mathf.Clamp((distance - 30) / 50, 0f, 1f) * thrust);
    }
}

Answer 1

You can do this by keeping track of a desired position relative to the player's view, or current frame of reference:

Vector3 desiredOffsetFromPlayer;

You can update this variable to make it approach the player or follow any arbitrary curve in its holding pattern in front of the player.

Then you can transform this into an actual world position like so:

Vector3 desiredPosition = player.transform.TransformPoint(desiredOffsetFromPlayer);

Now you can apply your navigation forces to seek toward that point (in FixedUpdate, for consistency regardless of framerate), or use physics queries to find the closest you can get to that point without clipping an obstacle.

Here's one potential way to do it:

void FixedUpdate() {
    // If you want to animate the holding position, update desired offset here.

    Vector3 desiredPosition = player.transform.TransformPoint(desiredOffsetFromPlayer);

    // How do we need to move to reach our target in this physics step?
    // You can also add the player velocity here to match course with them.
    Vector3 desiredVelocity = (desiredPosition - rb.position)/Time.deltaTime;

    // Clamp this within what our vessel is physically allowed to do.
    // (Here I assume we can thrust in any direction without turning around first)
    float maxDeltaV = maxThrust * Time.deltaTime;
    Vector3 deltaV = Vector3.ClampMagnitude(desiredVelocity - rb.velocity, maxDeltaV);

    // Accelerate to apply the needed correction.
    rb.AddForce(deltaV, ForceMode.VelocityChange);
}