UnityShader使用图像叠加实现运动模糊

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 MotionBlur : PostEffectsBase{  public Shader MotionBlurShader; private Material _motionBlurMaterial = null;  public Material Material {  get  {   _motionBlurMaterial = CheckShaderAndCreateMaterial(MotionBlurShader, _motionBlurMaterial);   return _motionBlurMaterial;  } }   //定义运动模糊在混合图像时使用的模糊参数,值越大，拖尾越明显，但过大会完全替代当前帧的渲染结果，所以最大为0.9 [Range(0.0f, 0.9f)] public float BlurAmount = 0.5f;  //定义一个RenderTexture类型的变量，保存之前图像叠加的结果 private RenderTexture _accumulationTexture; //当脚本不运行时，立即销毁，这样在下一次开始运行时会重新叠加图像 void OnDisable() {  DestroyImmediate(_accumulationTexture); }  void OnRenderImage(RenderTexture src, RenderTexture dest) {  if (Material != null)  {   //判断用于混合图像的_accumulationTexture是否为空，或者是否与当前屏幕分辨率相等   //如果不满足，需要重新创建   if (_accumulationTexture == null || _accumulationTexture.width != src.width ||    _accumulationTexture.height != src.height)   {    //立即销毁当前_accumulationTexture    DestroyImmediate(_accumulationTexture);    //创建一个与当前屏幕分辨率相等的    _accumulationTexture = new RenderTexture(src.width, src.height, 0);    //由于我们自己控制这个变量的销毁，所以不需要他显示在Hierarchy中，也不需要保存在场景中    _accumulationTexture.hideFlags = HideFlags.HideAndDontSave;    //使用当前的帧图像初始化_accumulationTexture    Graphics.Blit(src, _accumulationTexture);   }    //对渲染纹理进行恢复操作，发生在渲染的纹理而该纹理又没有被提前清空或销毁的情况下   //运动模糊每次调用OnRenderImage函数，都需要把当前纹理与_accumulationTexture中的图像混合，所以_accumulationTexture不需要被提前清空   _accumulationTexture.MarkRestoreExpected();    //将参数传给材质   Material.SetFloat("_BlurAmount", 1.0f - BlurAmount);    //把当前的屏幕图像叠加到_accumulationTexture   Graphics.Blit(src, _accumulationTexture, Material);   //把叠加后的图像输出到屏幕   Graphics.Blit(_accumulationTexture, dest);  }  else  {   Graphics.Blit(src, dest);  } }}

Shader "Unity Shaders Book/Chapter 12/MotionBlur"{ Properties { _MainTex ("Base (RGB)", 2D) = "white" {}  //混合系数 _BlurAmount("Blur Amount", Float) = 1.0 } SubShader { CGINCLUDE #include "UnityCG.cginc"  sampler2D _MainTex; fixed _BlurAmount;  //定义顶点着色器 struct v2f { float4 pos : SV_POSITION; half2 uv : TEXCOORD0; };  v2f vert(appdata_img v) { v2f o; o.pos = UnityObjectToClipPos(v.vertex); o.uv = v.texcoord; return o; }  //定义第一个片元着色器，用于更新渲染纹理的RGB通道部分 fixed4 fragRGB(v2f i) : SV_Target{ //将A通道的值设为_BlurAmount,这样在后面混合时可直接使用透明通道进行混合 return fixed4(tex2D(_MainTex, i.uv).rgb, _BlurAmount); }  //定义第二个片元着色器，用于更新渲染纹理的A通道部分 half4 fragA(v2f i) : SV_Target{ //直接返回采样结果，为了维护渲染纹理的透明通道值，不让其受到混合时使用的透明度值的影响 return tex2D(_MainTex, i.uv); }  ENDCG  ZTest Always Cull Off Zwrite Off //第一个Pass,用于更新渲染纹理的RGB通道 Pass { Blend SrcAlpha OneMinusSrcAlpha ColorMask RGB CGPROGRAM #pragma vertex vert #pragma fragment fragRGB ENDCG }  //第二个Pass,用于更新渲染纹理的A通道 Pass { Blend One Zero ColorMask A CGPROGRAM #pragma vertex vert #pragma fragment fragA ENDCG } } Fallback Off}