写出在unity中实现离轴投影效果的代码

离轴投影需要在相机上设置一个裁剪平面，将场景分为两部分进行投影。在Unity中实现离轴投影效果的代码如下：

using UnityEngine;

public class ObliqueProjection : MonoBehaviour
{
    public float clippingPlaneDistance = 0.1f;
    public Vector3 clippingPlaneNormal = Vector3.up;

    private Camera cam;

    private void Start()
    {
        cam = GetComponent<Camera>();
    }

    private void LateUpdate()
    {
        // Calculate the matrix for the oblique projection
        Matrix4x4 matrix = cam.projectionMatrix;
        Vector4 plane = new Vector4(clippingPlaneNormal.x, clippingPlaneNormal.y, clippingPlaneNormal.z, -clippingPlaneDistance);
        Vector4 clipPlane = matrix.inverse * new Vector4(Mathf.Sign(plane.x), Mathf.Sign(plane.y), 1.0f, 1.0f);
        matrix = CalculateObliqueMatrix(matrix, clipPlane);

        // Apply the oblique projection matrix to the camera
        cam.projectionMatrix = matrix;
    }

    private Matrix4x4 CalculateObliqueMatrix(Matrix4x4 projection, Vector4 clipPlane)
    {
        Vector4 q = projection.inverse * new Vector4(
            Mathf.Sign(clipPlane.x),
            Mathf.Sign(clipPlane.y),
            1.0f,
            1.0f
        );
        
        Vector4 c = clipPlane * (2.0f / Vector4.Dot(clipPlane, q));
        
        projection[2] = c.x - projection[3];
        projection[6] = c.y - projection[7];
        projection[10] = c.z - projection[11];
        projection[14] = c.w - projection[15];
        
        return projection;
    }
}

其中`clippingPlaneDistance`和`clippingPlaneNormal`是裁剪平面的距离和法向量。在`LateUpdate()`方法中计算出离轴投影的矩阵，并将其应用到相机上。`CalculateObliqueMatrix()`方法计算出用于进行离轴投影的矩阵。