放大或缩小相机

Question

I have a ball which is focusing by a camera at random height and distance. On mouse scroll I want to zoom in-out my camera towards the ball. I have tried this weird code and its behaving weird as I expected.

void ZoomInOut() { 
    if(Input.GetAxis("Mouse ScrollWheel") > 0){
        Debug.Log("mouse scroll wheel greater");
        distance += 20.0f;
        Vector3 negDistance = new Vector3(targetFollow.transform.position.x, targetFollow.transform.position.y, -distance);
        Vector3 pos = transform.rotation * negDistance + targetFollow.transform.position;
        transform.position = pos;
    }
    if(Input.GetAxis("Mouse ScrollWheel") < 0){
        Debug.Log("mouse scroll wheel less");
        distance -= 20.0f;
        Vector3 negDistance = new Vector3(targetFollow.transform.position.x, targetFollow.transform.position.y, -distance);
        Vector3 pos = transform.rotation * negDistance + targetFollow.transform.position;
        transform.position = pos;
    }
}

Answer 1

If want to zoom directly forwards/backwards, can use this: ZoomWithMouse.cs

It just moves camera along transform.forward axis.

using UnityEngine;

// Zoom forward and backward with mousewheel, Attach this script to camera
public class ZoomWithMouse : MonoBehaviour
{
    public float zoomSpeed = 300;
    void Update()
    {
        var mouseScroll = Input.GetAxis("Mouse ScrollWheel");

        if (mouseScroll!=0)
        {
            transform.Translate(transform.forward * mouseScroll * zoomSpeed * Time.deltaTime, Space.Self);
        }
    }
}

source: https://github.com/UnityCommunity/UnityLibrary/blob/master/Scripts/Camera/ZoomWithMouse.cs

Answer 2

using UnityEngine;
using System.Collections;

public class Zoom : MonoBehaviour
{
    private float _speed = 10;

private void Update()
{
    float mouseScroll = Input.GetAxis("Mouse ScrollWheel");

    if (mouseScroll!=0)
    {
        transform.Translate(Mathf.Sign(mouseScroll) * transform.forward * _speed * Time.deltaTime, Space.World);
    }
}
}