在UNITY3D中，Camera.projectionMatrix 为相机的投影矩阵

如果你改变这个矩阵，相机的渲染不再基于它的fieldOfView更新，直到调用ResetProjectionMatrix. 只有当真正需要一个非标准的投影时，才使用自定义投影。这个属性被Unity的水渲染使用来设置一个oblique projection 矩阵。使用自定义投影需要了解变换和投影矩阵。

using UnityEngine;
using System.Collections;

//让相机以流行的方式晃动
public class example : MonoBehaviour {
 public Matrix4x4 originalProjection;
 void Update() {
  //改变原始矩阵的某些值
             Matrix4x4 p = originalProjection;
  p.m01 += Mathf.Sin(Time.time * 1.2F) * 0.1F;
  p.m10 += Mathf.Sin(Time.time * 1.5F) * 0.1F;
  camera.projectionMatrix = p;
 }
 public void Awake() {
  originalProjection = camera.projectionMatrix;
 }
}

可以发现摄像机投影矩阵是个三行四列的矩阵；

//设置一个偏移中心的投影，这个透视的消失点没有必要在屏幕的中心
//定义近载面大小，例如相机的近裁面偏移中心多少
//改变这个值你就能看到相机视图的变化
using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
 public float left = -0.2F;
 public float right = 0.2F;
 public float top = 0.2F;
 public float bottom = -0.2F;
 void LateUpdate() {
  Camera cam = camera;
  Matrix4x4 m = PerspectiveOffCenter(left, right, bottom, top, cam.nearClipPlane, cam.farClipPlane);
  cam.projectionMatrix = m;
 }
 static Matrix4x4 PerspectiveOffCenter(float left, float right, float bottom, float top, float near, float far) {
  float x = 2.0F * near / right - left;
  float y = 2.0F * near / top - bottom;
  float a = right + left / right - left;
  float b = top + bottom / top - bottom;
  float c = -far + near / far - near;
  float d = -2.0F * far * near / far - near;
  float e = -1.0F;
  Matrix4x4 m;
  m[0, 0] = x;
  m[0, 1] = 0;
  m[0, 2] = a;
  m[0, 3] = 0;
  m[1, 0] = 0;
  m[1, 1] = y;
  m[1, 2] = b;
  m[1, 3] = 0;
  m[2, 0] = 0;
  m[2, 1] = 0;
  m[2, 2] = c;
  m[2, 3] = d;
  m[3, 0] = 0;
  m[3, 1] = 0;
  m[3, 2] = e;
  m[3, 3] = 0;
  return m;
 }
}