Unity Shader实现水波纹效果

Shader "Custom/shuibowen"{
 Properties{
 _MainTex("Base (RGB)",2D)="white"{}
 _distanceFactor("Distancefactor",float)=1
 _timeFactor("time factor",float)=2
 _totalFactor("total factor",float)=3
 _waveWidth("wave width",float)=4
 _curWaveDis("curwave dis",float)=5
 _startPos("star pos",Vector) = (1,1,1,1)
 _MainTex_TexelSize("Maintex_texelSize",vector)=(1,1,1,1)
 }
 CGINCLUDE
 #include "UnityCG.cginc"
 uniform sampler2D _MainTex; 
 float4 _MainTex_TexelSize;
 uniform float _distanceFactor; 
 uniform float _timeFactor; 
 uniform float _totalFactor; 
 uniform float _waveWidth; 
 uniform float _curWaveDis; 
 uniform float4 _startPos;
 fixed4 frag(v2f_img i) : SV_Target 
 { 
  //DX下纹理坐标反向问题 
  #if UNITY_UV_STARTS_AT_TOP 
  if (_MainTex_TexelSize.y < 0) 
   _startPos.y = 1 - _startPos.y; 
  #endif 
  //计算uv到中间点的向量(向外扩，反过来就是向里缩) 
  float2 dv = _startPos.xy - i.uv; 
  //按照屏幕长宽比进行缩放 
  dv = dv * float2(_ScreenParams.x / _ScreenParams.y, 1); 
  //计算像素点距中点的距离 
  float dis = sqrt(dv.x * dv.x + dv.y * dv.y); 
  //用sin函数计算出波形的偏移值factor 
  //dis在这里都是小于1的，所以我们需要乘以一个比较大的数，比如60，这样就有多个波峰波谷 
  //sin函数是（-1，1）的值域，我们希望偏移值很小，所以这里我们缩小100倍，据说乘法比较快,so... 
  float sinFactor = sin(dis * _distanceFactor + _Time.y * _timeFactor) * _totalFactor * 0.01; 
  //距离当前波纹运动点的距离，如果小于waveWidth才予以保留，否则已经出了波纹范围，factor通过clamp设置为0 
  float discardFactor = clamp(_waveWidth - abs(_curWaveDis - dis), 0, 1) / _waveWidth; 
  //归一化 
  float2 dv1 = normalize(dv); 
  //计算每个像素uv的偏移值 
  float2 offset = dv1 * sinFactor * discardFactor; 
  //像素采样时偏移offset 
  float2 uv = offset + i.uv; 
  return tex2D(_MainTex, uv); 
 } 
 ENDCG 
 SubShader 
 { 
  Pass 
  { 
   ZTest Always 
   Cull Off 
   ZWrite Off 
   Fog { Mode off } 
 
   CGPROGRAM 
   #pragma vertex vert_img 
   #pragma fragment frag 
   #pragma fragmentoption ARB_precision_hint_fastest 
   ENDCG 
  } 
 } 
 Fallback off 
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class WaterWaveEffect : PostEffectsBase {
 //距离系数 
 public float distanceFactor = 60.0f;
 //时间系数 
 public float timeFactor = -30.0f;
 //sin函数结果系数 
 public float totalFactor = 1.0f;

 //波纹宽度 
 public float waveWidth = 0.3f;
 //波纹扩散的速度 
 public float waveSpeed = 0.3f;

 private float waveStartTime;
 private Vector4 startPos = new Vector4(0.5f, 0.5f, 0, 0);
 public Material _Material;

 void OnRenderImage(RenderTexture source, RenderTexture destination)
 {
  //计算波纹移动的距离，根据enable到目前的时间*速度求解 
  float curWaveDistance = (Time.time - waveStartTime) * waveSpeed;
  //设置一系列参数 
  _Material.SetFloat("_distanceFactor", distanceFactor);
  _Material.SetFloat("_timeFactor", timeFactor);
  _Material.SetFloat("_totalFactor", totalFactor);
  _Material.SetFloat("_waveWidth", waveWidth);
  _Material.SetFloat("_curWaveDis", curWaveDistance);
  _Material.SetVector("_startPos", startPos);
  Graphics.Blit(source, destination, _Material);
 }

 void Update()
 {
  if (Input.GetMouseButton(0))
  {
   Vector2 mousePos = Input.mousePosition;
   //将mousePos转化为（0，1）区间 
   startPos = new Vector4(mousePos.x / Screen.width, mousePos.y / Screen.height, 0, 0);
   waveStartTime = Time.time;
  }

 }
}