FPS控制器中的Unity / C＃奇怪故障

Question

i have a weird glitch, when i walk down from a corner (i dont press jump), the player will falling down with very fast speed. If i jump, then everything goes normal. (Its Quill18 FPS controller, i learn from there so thats why i dont use the built in controller instead)

using UnityEngine;
using System.Collections;    
[RequireComponent (typeof(CharacterController))]
public class FirstPersonController : MonoBehaviour
{

    public float movementSpeed = 5.0f;
    public float mouseSensitivity = 5.0f;
    public float jumpSpeed = 20.0f;

    float verticalRotation = 0;
    public float upDownRange = 60.0f;

    float verticalVelocity = 0;

    CharacterController characterController;

    // Use this for initialization
    void Start()
    {
//     Screen.lockCursor = true;
       characterController = GetComponent<CharacterController>();
    }

    // Update is called once per frame
    void Update() 
    {
       // Rotation

       float rotLeftRight = Input.GetAxis("Mouse X") * mouseSensitivity;
       transform.Rotate(0, rotLeftRight, 0);

       verticalRotation -= Input.GetAxis("Mouse Y") * mouseSensitivity;
       verticalRotation = Mathf.Clamp(verticalRotation, -upDownRange, upDownRange);
       Camera.main.transform.localRotation = Quaternion.Euler(verticalRotation, 0, 0);

       // Movement

       float forwardSpeed = Input.GetAxis("Vertical") * movementSpeed;
       float sideSpeed = Input.GetAxis("Horizontal") * movementSpeed;

       verticalVelocity += Physics.gravity.y * Time.deltaTime;

       if (characterController.isGrounded && Input.GetButton("Jump"))
       {
          verticalVelocity = jumpSpeed;
       }

       Vector3 speed = new Vector3(sideSpeed, verticalVelocity, forwardSpeed ;

       speed = transform.rotation * speed;

       characterController.Move(speed * Time.deltaTime);
    }
}

Answer 1

The problem is that every frame you're running this line:

verticalVelocity += Physics.gravity.y * Time.deltaTime;

Thus, you're gaining "momentum" each second, and it wont stop ever until you jump because you're "resetting" the Y velocity to a normal value. I've ran into this problem before, and it can be fixed simply by only adding the Y velocity when you're not grounded. You can use Raycast to check if you have ground, and if you dont, increase verticalVelocity by that amount.