Why does my player fall very slowly because of script?

Question

I have a problem with when my player needs to fall. The player is falling very slowly. I got that problem is in my script because when I turn off the script, the player is falling in normal acceleration.

Can you help me? I tried to figure out the problem in my code and tried to use ChatGPT for help, but I don't understand. I am new at Unity. Here is my code:

using System.Collections;
using System.Collections.Generic;
using Unity.VisualScripting;
using UnityEngine;

public class Player : MonoBehaviour
{
    Rigidbody rb;
    public GameObject trigger;
    public GameObject camera;
    public float speed;
    public float rotationSpeed;
    public Animator anim;
    public float jump;
    public bool isGrounded = true;

    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

---
    // Update is called once per frame
    void FixedUpdate()
    {

        


        float horizontalInput = Input.GetAxis("Horizontal");
        float verticalInput = Input.GetAxis("Vertical");

        // Calculate the movement direction based on input
        Vector3 cameraForward = Vector3.ProjectOnPlane(camera.transform.forward, Vector3.up).normalized;
        Vector3 cameraRight = Vector3.ProjectOnPlane(camera.transform.right, Vector3.up).normalized;
        Vector3 moveDirection = cameraForward * verticalInput + cameraRight * horizontalInput;
        moveDirection.Normalize();

        if (moveDirection != Vector3.zero)
        {
            // Calculate the target rotation based on the movement direction
            Quaternion targetRotation = Quaternion.LookRotation(moveDirection, Vector3.up);

            // Smoothly rotate the character towards the target rotation
            transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, rotationSpeed * Time.deltaTime);
        }

        // Move the character
        rb.velocity = moveDirection * speed;


        if(Input.GetKey(KeyCode.W) || Input.GetKey(KeyCode.S) || Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.D))
        {
            anim.SetInteger("swr", 1);
        }
        else
        {
            anim.SetInteger("swr", 0);
        }

        
    }

    //private void OnCollisionEnter(Collision collision)
    //{
      //  if (trigger.CompareTag("Cloud"))
      //  {
             //   isGrounded = true;
     //   }
     //   else
     ///   {
      //      isGrounded = false;
      //  }
    //}

}

Answer 1

You do

 rb.velocity = moveDirection * speed;

which completely ignores gravity. You copletely overrule the velocity with the new one which is only based on input

You should probably maintain the Y axis component and do e.g.

var velocity = moveDirection * speed;
velocity.y = rb.velocity.y;
rb.velocity = velocity;

---

Additionally you also shouldn't use

transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, rotationSpeed * Time.deltaTime);
  

but rather also for that one go through

rb.MoveRotation(Quaternion.RotateTowards(rb.rotation, targetRotation, rotationSpeed * Time.deltaTime));