Unity 相机 2D视角 与3D 视角 自由动态 切换

再游戏运行的时候，往往需要 在 正交Orthographic (无消失点投影) 与正交Orthographic (无消失点投影) 两个视角中来回转化。 以达到 不同的 2D 与 3D 视角。

So! 今天的 实例代码就是 描述了 这一个功能：

---

using UnityEngine;

public enum Views
{
    _2DView = 1,
    _3DView
}
 public class BackupCameraProjectionChange
 {
    /// <summary>
    /// 相机透视改变是否触发(调用只需把此值改为true)
    /// </summary>
    public bool ChangeProjection = false;
    private bool _changing = false;
    private float ProjectionChangeTime = 0.5f;
    private float _currentT = 0.0f;
    private Camera m_Camera;

protected Views cur_Views = Views._3DView;

public Views GetCurViews
{
    get
    {
        return cur_Views;
    }
}

public BackupCameraProjectionChange(Camera camera = null , float speed = 0.5f)
{
    ProjectionChangeTime = speed;
    if (m_Camera == null && camera == null)
    {
        m_Camera = Camera.main;
    }
    else
    {
        m_Camera = camera;
    }
}

///这个 Update 需要在 其他继承自 MonoBehaviour 类的 Update 中 调用
public void Update()
{
    if (m_Camera == null)
        return;

    if (_changing)
    {
        ChangeProjection = false;
    }
    else if (ChangeProjection)
    {
        _changing = true;
        _currentT = 0.0f;
    }

    LateUpdate();
}


void LateUpdate()
{
    if (!_changing)
    {
        return;
    }
    //将当前的 是否正视图值 赋值给currentlyOrthographic变量
    bool currentlyOrthographic = m_Camera.orthographic;

    //定义变量存放当前摄像机的透视和正视矩阵信息；
    Matrix4x4 orthoMat, persMat;
    if (currentlyOrthographic)//如果当前摄像机为正视状态，则切换为3D
    {
        orthoMat = m_Camera.projectionMatrix; //保留 2D矩阵信息

        m_Camera.orthographic = false;  //为 3D
        m_Camera.ResetProjectionMatrix();
        persMat = m_Camera.projectionMatrix;   //保留 3D 矩阵信息

        cur_Views = Views._3DView;
    }
    else//否则当前摄像机为透视状态， 则切换为2D
    {
        persMat = m_Camera.projectionMatrix; //保留 3D 矩阵信息

        m_Camera.orthographic = true;    //为2D
        m_Camera.ResetProjectionMatrix();
        orthoMat = m_Camera.projectionMatrix;  //保留 2D矩阵信息

        cur_Views = Views._2DView;
    }
    m_Camera.orthographic = currentlyOrthographic;


    _currentT += (Time.deltaTime / ProjectionChangeTime);
    if (_currentT < 1.0f)
    {
        if (currentlyOrthographic)
        {
            m_Camera.projectionMatrix = MatrixLerp(orthoMat, persMat, _currentT * _currentT);  //从2D 到 3D
        }
        else
        {
            m_Camera.projectionMatrix = MatrixLerp(persMat, orthoMat, Mathf.Sqrt(_currentT)); //从3D 到 2D
        }
    }
    else
    {
        _changing = false;
        m_Camera.orthographic = !currentlyOrthographic;  //取反
        m_Camera.ResetProjectionMatrix();   // 重置
    }
}



private Matrix4x4 MatrixLerp(Matrix4x4 from, Matrix4x4 to, float t)
{
    t = Mathf.Clamp(t, 0.0f, 1.0f);
    Matrix4x4 newMatrix = new Matrix4x4();
    newMatrix.SetRow(0, Vector4.Lerp(from.GetRow(0), to.GetRow(0), t));
    newMatrix.SetRow(1, Vector4.Lerp(from.GetRow(1), to.GetRow(1), t));
    newMatrix.SetRow(2, Vector4.Lerp(from.GetRow(2), to.GetRow(2), t));
    newMatrix.SetRow(3, Vector4.Lerp(from.GetRow(3), to.GetRow(3), t));
    return newMatrix;
}
}

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