[游戏开发-学习笔记]菜鸟慢慢飞（四）-Camera

游戏开发中，主相机应该是最重要的GameObject之一，毕竟游戏呈现给玩家，就是通过它。
相机的使用，在不同的游戏中，有很大的不同。这里总结一下自己学到的一些相关知识。

固定位置-游戏过程中相机的Transform属性不改变。

• 调整好位置后就不要动了,一般使用正交相机，即Camera-Projection选择Orthographic。Unity Manual-Camera
  适用：2D游戏。比如飞机大战，消消乐。
• 游戏开始后，相机追踪某一物体，然后固定不动。
  游戏开始后，我们才能确定追踪物体的位置，先看代码：

 using UnityEngine;

 public class CameraController : MonoBehaviour
 {
     public GameObject player;
     private Vector3 offset;
     void Start ()
     {
         offset = transform.position - player.transform.position;
     }
     void LateUpdate ()
     {
         transform.position = player.transform.position + offset;
     }
 }

适用：固定视角的3D游戏。

3D视角-围绕一个中心随意旋转

先看代码：

using UnityEngine;

public class CameraContorller : MonoBehaviour
{
    /// <summary>
    /// 追踪目标
    /// </summary>
    public Transform target;
    /// <summary>
    /// 旋转速度
    /// </summary>
    public float xSpeed = , ySpeed = ;
    /// <summary>
    /// 缩放速度
    /// </summary>
    public float mSpeed = ;
    /// <summary>
    /// 最小/最大限制角度
    /// </summary>
    public float yMinLimit = -, yMaxLimit = ;
    /// <summary>
    /// 是否使用插值运算
    /// </summary>
    public bool needDamping = true;
    /// <summary>
    /// 速度
    /// </summary>
    public float damping = 5.0f;

    /// <summary>
    /// 观察距离
    /// </summary>
    private float distance = ;
    /// <summary>
    /// 最小/最大观察距离
    /// </summary>
    private float minDistance = , maxDistance = ;
    /// <summary>
    /// 旋转角度
    /// </summary>
    private float x = 0.0f, y = 0.0f;

    void Start()
    {
        Vector3 angles = transform.eulerAngles;
        x = angles.y;
        y = angles.x;
        //根据相机的初始位置初始化距离，最大距离，最小距离；
        Vector3 offset = transform.position - target.position;
        distance = offset.magnitude;
        minDistance = distance / ;
        maxDistance = distance * ;
    }

    void LateUpdate()
    {
        if (target)
        {
            if (Input.GetMouseButton())//0-左键,1-右键,2-中键
            {
                x += Input.GetAxis("Mouse X") * xSpeed * 0.02f;
                y -= Input.GetAxis("Mouse Y") * ySpeed * 0.02f;

                y = ClampAngle(y, yMinLimit, yMaxLimit);
            }
            distance -= Input.GetAxis("Mouse ScrollWheel") * mSpeed;
            distance = Mathf.Clamp(distance, minDistance, maxDistance);

            Quaternion rotation = Quaternion.Euler(y, x, 0.0f);
            Vector3 disVector = new Vector3(0.0f, 0.0f, -distance);
            Vector3 position = rotation * disVector + target.position;
            if (needDamping)
            {
                transform.rotation = Quaternion.Lerp(transform.rotation, rotation, Time.deltaTime * damping);
                Vector3 transformTemp = Vector3.Lerp(transform.position, position, Time.deltaTime * damping);
                if (transformTemp.y <= )//如果相机位置在“水平面”以下，强制设置到水平面。
                {
                    transform.position = new Vector3(transformTemp.x, , transformTemp.z);
                }
                else
                {
                    transform.position = transformTemp;
                }
            }
            else
            {
                transform.rotation = rotation;
                if (position.y <= )//如果相机位置在“水平面”以下，强制设置到水平面。
                {
                    transform.position = new Vector3(position.x, , position.z);
                }
                else
                {
                    transform.position = position;
                }
            }
        }
    }

    static float ClampAngle(float angle, float min, float max)
    {
        if (angle < -)
            angle += ;
        if (angle > )
            angle -= ;
        return Mathf.Clamp(angle, min, max);
    }
}

大部分3D游戏中，我这样理解：主角看作球心，球半径玩家可以自己改变，相机的位置就在“地面”以上的半球球体上。
上面这段代码基本做到了这个要求，并在相机到“地面”的时候有抬头看的效果。
代码有点问题，开始游戏后相机会跳动两次，暂时放到自己的问题清单中。

其他用法

官方教程Tanks tutorial 中有个不常见的用法。
不管两个Tank如何移动，相机通过前后缩放，大小缩放保证两个Tank肯定在相机视野内。
主要代码：（官方代码写得好啊）

private void Move ()
        {
            // Find the average position of the targets.
            FindAveragePosition ();

            // Smoothly transition to that position.
            transform.position = Vector3.SmoothDamp(transform.position, m_DesiredPosition, ref m_MoveVelocity, m_DampTime);
        }

        private void FindAveragePosition ()
        {
            Vector3 averagePos = new Vector3 ();
            int numTargets = ;

            // Go through all the targets and add their positions together.
            for (int i = ; i < m_Targets.Length; i++)
            {
                // If the target isn't active, go on to the next one.
                if (!m_Targets[i].gameObject.activeSelf)
                    continue;

                // Add to the average and increment the number of targets in the average.
                averagePos += m_Targets[i].position;
                numTargets++;
            }

            // If there are targets divide the sum of the positions by the number of them to find the average.
            if (numTargets > )
                averagePos /= numTargets;

            // Keep the same y value.
            averagePos.y = transform.position.y;

            // The desired position is the average position;
            m_DesiredPosition = averagePos;
        }

        private void Zoom ()
        {
            // Find the required size based on the desired position and smoothly transition to that size.
            float requiredSize = FindRequiredSize();
            m_Camera.orthographicSize = Mathf.SmoothDamp (m_Camera.orthographicSize, requiredSize, ref m_ZoomSpeed, m_DampTime);
        }

        private float FindRequiredSize ()
        {
            // Find the position the camera rig is moving towards in its local space.
            Vector3 desiredLocalPos = transform.InverseTransformPoint(m_DesiredPosition);

            // Start the camera's size calculation at zero.
            float size = 0f;

            // Go through all the targets...
            for (int i = ; i < m_Targets.Length; i++)
            {
                // ... and if they aren't active continue on to the next target.
                if (!m_Targets[i].gameObject.activeSelf)
                    continue;

                // Otherwise, find the position of the target in the camera's local space.
                Vector3 targetLocalPos = transform.InverseTransformPoint(m_Targets[i].position);

                // Find the position of the target from the desired position of the camera's local space.
                Vector3 desiredPosToTarget = targetLocalPos - desiredLocalPos;

                // Choose the largest out of the current size and the distance of the tank 'up' or 'down' from the camera.
                size = Mathf.Max(size, Mathf.Abs(desiredPosToTarget.y));

                // Choose the largest out of the current size and the calculated size based on the tank being to the left or right of the camera.
                size = Mathf.Max(size, Mathf.Abs(desiredPosToTarget.x) / m_Camera.aspect);
            }

            // Add the edge buffer to the size.
            size += m_ScreenEdgeBuffer;

            // Make sure the camera's size isn't below the minimum.
            size = Mathf.Max (size, m_MinSize);

            return size;
        }

暂时放下的内容

Unity的相机相关：

• Screen Space Ambient Obscurance
• Bloom
• TiltShift
• VignetteAndChromaticAberration
• Color Correction Curves