Unity3D第一人称视角及移动，Y轴保持不变

创建一个Capsule，在Capsule下面创建一个Camera：

 在Capsule下增加Character Controller，新增FPLook.cs（鼠标控制的第一人称视角）和FPMove.cs（键盘WSAD控制的前后左右移动）：

 FPLook.cs：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FPLook : MonoBehaviour
{
    //视野转动速度
    float speedX = 10f;
    float speedY = 10f;　　//上下观察范围
    float minY = -60;
    float maxY = 60;
　　//观察变化量
    float rotationX;
    float rotationY;

    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update () 
    {
        rotationX +=  Input.GetAxis ("Mouse X")*speedX;
        rotationY +=  Input.GetAxis ("Mouse Y")*speedY;
        if (rotationX < 0) {
            rotationX += 360;
        }
        if (rotationX >360) {
            rotationX -= 360;
        }
        rotationY = Mathf.Clamp (rotationY, minY, maxY);　　
        transform.localEulerAngles = new Vector3 (-rotationY, rotationX, 0);
    }
}

 FPMove.cs：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FPMove : MonoBehaviour
{
    float speed = 5f;　　//移动速度
    private CharacterController characterController;

    // Start is called before the first frame update
    void Start()
    {
        characterController = this.GetComponent();
    }

    // Update is called once per frame
    void Update()
    {
        //键盘控制前后
        float x = Input.GetAxis("Horizontal") * Time.deltaTime * speed;//左右移动
        float z = Input.GetAxis("Vertical") * Time.deltaTime * speed;//前后移动

        Vector3 movement = new Vector3 (x,0,z);
        movement = transform.TransformDirection(movement);//旋转之后的转向

        Vector3 newMovement = new Vector3 (movement.x,0,movement.z);
        characterController.Move(newMovement);//移动
    }
}

起飞降落模式：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FPMove : MonoBehaviour
{
    float speed = 5f;　　//移动速度
    private CharacterController characterController;

    // Start is called before the first frame update
    void Start()
    {
        characterController = this.GetComponent();
    }

    // Update is called once per frame
    void Update()
    {
        //键盘控制前后
        float x = Input.GetAxis("Horizontal") * Time.deltaTime * speed;//左右移动
        float z = Input.GetAxis("Vertical") * Time.deltaTime * speed;//前后移动
        float y = 0;

        Vector3 movement = new Vector3 (x,y,z);
        movement = transform.TransformDirection(movement);//旋转之后的转向

        if(transform.localPosition.y >= 0)
        {
            y = movement.y;
        }
        else
        {
            y = 0.002f;//根据实际情况调整
        }

        Vector3 newMovement = new Vector3 (movement.x,y,movement.z);
        characterController.Move(newMovement);//移动
    }
}