Limit velocity of a rigidbody on the XZ plane

Questions & Answers
1

I’m new to unity, and I’ve been trying to make a player controller that makes the player able to move in the XZ plane with a maximum velocity, independently of their velocity in the Y axis. So far this is what I’ve got, partly through copying from examples and just trial and error:

using UnityEngine;
using UnityEngine.InputSystem;

public class PlayerMovement : MonoBehaviour
{
    [SerializeField]
    private float _moveSpeed;
    [SerializeField]
    private float _moveAcceleration;
    [SerializeField]
    private Rigidbody _rb;

    private void Update()
    {
        Gamepad gamepad = Gamepad.current;
        if (gamepad == null)
            return;

        Vector2 leftStick = gamepad.leftStick.ReadValue();

        Move(leftStick);
    }

    private void Move(Vector2 direction)
    {
        // The Quaternion.Euler(0, -45, 0) is used to correct for perspective,
        //  as my camera is pointed at 45° with respect to the player.
        Vector3 _moveDirection = Quaternion.Euler(0, -45, 0) * new Vector3(direction.x, 0, direction.y);

         float _scaledMoveAcceleration = _moveAcceleration * Time.deltaTime;
        _rb.AddForce(_moveDirection.x * _scaledMoveAcceleration, 0, _moveDirection.z * _scaledMoveAcceleration, ForceMode.VelocityChange);

        //This is what I'm using to limit the player's velocity
        _rb.velocity = Vector3.ClampMagnitude(_rb.velocity, _moveSpeed);

    }
}

As you can see, my player has a Rigidbody component I linked to the script in the inspector. I also have a jump method that simply adds a vertical velocity when a button is pressed, but I removed it for clarity.

My main problem is that the player’s movement on the Y axis isn’t independant of its movement on the XZ plane, so if I drop the player from a cliff, it ends up falling faster if I don’t move the player in mid-air, and it stops accelerating when it reaches a the max velocity I set. I know this is caused by my usage of Vector3.ClampMagnitude, but I haven’t found an alternative that fits my needs.

2

Try clamping the magnitude of the velocity separately for X/Z vs Y axis

Vector3 xzVel = new Vector3(_rb.velocity.x, 0, _rb.velocity.z);
Vector3 yVel = new Vector3(0, _rb.velocity.y, 0);

xzVel = Vector3.ClampMagnitude(xzVel, _movespeed);
yVel = Vector3.ClampMagnitude(yVel, maxVertSpeed);

_rb.velocity = xzVel + yVel;