using UnityEngine; 
using System.Collections; 
 
public class Translating : MonoBehaviour { 
 
 public float speed = 10.0f; 
 public Vector3 startPoint = Vector3.zero; 
 public Vector3 endPoint = Vector3.zero; 
 public Vector3 lookAt = Vector3.zero; 
 public bool pingpong = true; 
 
 private Vector3 curEndPoint = Vector3.zero; 
 
 // Use this for initialization 
 void Start () { 
 transform.position = startPoint; 
 curEndPoint = endPoint; 
 } 
 
 // Update is called once per frame 
 void Update () { 
 transform.position = Vector3.Slerp(transform.position, curEndPoint, Time.deltaTime * speed); 
 transform.LookAt(lookAt); 
 if (pingpong) { 
  if (Vector3.Distance(transform.position, curEndPoint) < 0.001f) { 
  curEndPoint = Vector3.Distance(curEndPoint, endPoint) < Vector3.Distance(curEndPoint, startPoint) ? startPoint : endPoint; 
  } 
 } 
 } 
} 

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
 
public class MotionBlurWithDepthTexture : PostEffectsBase
{
 public Shader MotionBlurShader;
 private Material _motionBlurMaterial = null;
 
 public Material Material
 {
 get
 {
  _motionBlurMaterial = CheckShaderAndCreateMaterial(MotionBlurShader, _motionBlurMaterial);
  return _motionBlurMaterial;
 }
 }
 
 //定義運動模糊時模糊圖像使用的大小
 [Range(0.0f, 1.0f)] public float BlurSize = 0.5f;
 //定義一個Camera變量，獲取該腳本所在的攝像機組建，得到攝像機的視角和投影矩陣
 private Camera _myCamera;
 
 public Camera Camera
 {
 get
 {
  if (_myCamera == null)
  {
  _myCamera = GetComponent<Camera>();
  }
  return _myCamera;
 }
 }
 
 //定義一個變量保存 上一幀攝像機的視角 * 投影矩陣
 private Matrix4x4 _previousViewProjectionMatrix;
 
 //在OnEnable中設置攝像機的狀態(tài)，以獲得深度紋理
 void OnEnable()
 {
 Camera.depthTextureMode = DepthTextureMode.Depth;
 }
 
 void OnRenderImage(RenderTexture src, RenderTexture dest)
 {
 if (Material != null)
 {
  //將模糊大小傳給Shader
  Material.SetFloat("_BlurSize", BlurSize);
 
  //使用 視角 * 投影矩陣 對NDC（歸一化的設備坐標）下的頂點坐標進行變換，得到該像素在世界空間下的位置
  //計算前一幀與當前幀的位置差，生成該像素的速度
 
  //將 前一幀視角 * 投影矩陣 傳給Shader
  Material.SetMatrix("_PreviousViewProjectionMatrix", _previousViewProjectionMatrix);
  //計算 當前幀視角 * 投影矩陣
  //Camera.projectionMatrix獲得當前攝像機投影矩陣
  //Camera.worldToCameraMatrix獲得當前攝像機視角矩陣
  Matrix4x4 currentViewProjectionMartix = Camera.projectionMatrix * Camera.worldToCameraMatrix;
  //計算 當前幀視角 * 投影矩陣 的逆矩陣
  Matrix4x4 currentViewProjectionInverseMartix = currentViewProjectionMartix.inverse;
  //將當前幀視角 * 投影矩陣 的逆矩陣 傳遞給Shader
  Material.SetMatrix("_CurrentViewProjectionInverseMartix", currentViewProjectionInverseMartix);
  //將 當前幀視角 * 投影矩陣 保存為 前一幀視角 * 投影矩陣
  _previousViewProjectionMatrix = currentViewProjectionMartix;
 
  Graphics.Blit(src, dest, Material);
 }
 else
 {
  Graphics.Blit(src, dest);
 }
 }
}

Shader "Unity Shaders Book/Chapter 13/MotionBlurWithDepthTexture"
{
 Properties
 {
 _MainTex ("Base (RGB)", 2D) = "white" {}
 //模糊圖像時使用的參數(shù)
 _BlurSize ("Blur Size", Float) = 1.0
 
 //這里并沒有聲明_PreviousViewProjectionMatrix和_CurrentViewProjectionInverseMartix
 //是因為Unity并沒有提供矩陣類型的屬性，但仍然可以在CG代碼塊中定義這些矩陣，并從腳本中設置它們
 }
 SubShader
 {
 CGINCLUDE
 #include "UnityCG.cginc"
 
 sampler2D _MainTex;
 //使用_MainTex_TexelSize變量來對深度紋理的采樣坐標進行平臺化差異處理
 half4 _MainTex_TexelSize;
 //Unity傳遞來的深度紋理
 sampler2D _CameraDepthTexture;
 //聲明_PreviousViewProjectionMatrix和_CurrentViewProjectionInverseMartix
 float4x4 _PreviousViewProjectionMatrix;
 float4x4 _CurrentViewProjectionInverseMartix;
 half _BlurSize;
 
 //定義頂點著色器
 struct v2f {
 float4 pos : SV_POSITION;
 half2 uv : TEXCOORD0;
 //添加了用于深度紋理采樣的紋理坐標變量
 half2 uv_depth : TEXCOORD1;
 };
 
 v2f vert(appdata_img v) {
 v2f o;
 o.pos = UnityObjectToClipPos(v.vertex);
 o.uv = v.texcoord;
 o.uv_depth = v.texcoord;
 
 //平臺差異化處理
 #if UNITY_UV_STARTS_AT_TOP
 if (_MainTex_TexelSize.y < 0) {
 o.uv_depth.y = 1 - o.uv_depth.y;
 }
 #endif
 
 return o;
 }
 
 //定義片元著色器
 fixed4 frag(v2f i) : SV_Target{
 //使用宏和紋理坐標對深度紋理進行采樣，得到深度值
 float d = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, i.uv_depth);
 
 //構建當前像素的NDC坐標,xy坐標由像素的紋理坐標映射而來，z坐標由深度值d映射而來
 float4 H = float4(i.uv.x * 2 - 1, i.uv.y * 2 - 1, d * 2 - 1, 1);
 //使用 當前幀的視角 * 投影矩陣 的逆矩陣 對H進行變換
 float4 D = mul(_CurrentViewProjectionInverseMartix, H);
 //把結果除以它的w分量，得到該像素世界空間下的坐標
 float4 worldPos = D / D.w;
 
 //像素當前幀NDC坐標
 float4 currentPos = H;
 
 //使用 前一幀視角 * 投影矩陣 變換世界空間的的坐標worldPos，并除以它的w分量，得到前一幀的NDC坐標
 float4 previousPos = mul(_PreviousViewProjectionMatrix, worldPos);
 previousPos /= previousPos.w;
 
 //計算當前幀與前一幀在屏幕空間下的位置差，得到該像素的速度
 float2 velocity = (currentPos.xy - previousPos.xy) / 2.0f;
 
 //使用速度值對鄰域像素進行采樣，相加后取平均值得到一個模糊效果，使用_BlurSize控制采樣距離
 float2 uv = i.uv;
 float4 c = tex2D(_MainTex, uv);
 uv += velocity * _BlurSize;
 for (int it = 1; it < 3; it++, uv += velocity * _BlurSize) {
 float4 currentColor = tex2D(_MainTex, uv);
 c += currentColor;
 }
 c /= 3;
 
 return fixed4(c.rgb, 1.0);
 }
 ENDCG
 
 Pass
 {
 ZTest Always Cull Off ZWrite Off
 CGPROGRAM
 #pragma vertex vert
 #pragma fragment frag 
 ENDCG
 }
 }
 Fallback Off
}