Unity屏幕后处理（高斯模糊）

super1 · 发表于 2022-7-29 21:52

高斯模糊效果实现依然使用卷积操作，使用的卷积核为高斯核。具体计算流程书中解释如下：

这里为了提高性能，我们将一个5x5的高斯核拆分为两个长度为5的一维高斯核，从而降低采样次数已达到提升性能的目的。

挂载在相机上的后处理脚本实现如下：
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GaussianBlur : PostEffectsBase
{
public Shader GaussianBlurShader;

[Range(0,4)]
public int _Iterations = 3;  //模糊迭代（越大越模糊）
[Range(0.2f, 3.0f)]
public float _BlurSpread = 0.6f;
[Range(1,8)]
public int _DownSample = 2;

private Material _GaussianBlurMaterial;

public Material material
{
      get
      {
         _GaussianBlurMaterial = CheckShaderAndCreateMaterial(GaussianBlurShader, _GaussianBlurMaterial);
         return _GaussianBlurMaterial;
      }
}

////方案一（使用临时缓冲区存储过渡纹理）
// private void OnRenderImage(RenderTexture src, RenderTexture dest)
// {
//    if (material != null)
//    {
//       int rtW = src.width;
//       int rtH = src.height;
//       RenderTexture buffer = RenderTexture.GetTemporary(rtW, rtH, 0);
//
//       //渲染垂直方向的Pass
//       Graphics.Blit(src,buffer,material,0);
//       //渲染水平方向的Pass
//       Graphics.Blit(src,dest,material,1);
//
//       RenderTexture.ReleaseTemporary(buffer);
//    }
//    else
//    {
//       Graphics.Blit(src,dest);
//    }
// }

////方案二（在方案一的基础上，利用缩放对图像进行降采样，从而减少处理的像素个数提高性能）
// private void OnRenderImage(RenderTexture src, RenderTexture dest)
// {
//    if (material != null)
//    {
//       int rtW = src.width/_DownSample;
//       int rtH = src.height/_DownSample;
//       RenderTexture buffer = RenderTexture.GetTemporary(rtW, rtH, 0);
//       buffer.filterMode = FilterMode.Bilinear;
//       //渲染垂直方向的Pass
//       Graphics.Blit(src,buffer,material,0);
//       //渲染水平方向的Pass
//       Graphics.Blit(src,dest,material,1);
//
//       RenderTexture.ReleaseTemporary(buffer);
//    }
//    else
//    {
//       Graphics.Blit(src,dest);
//    }
// }

////方案三（在方案二的基础上，增加了高斯模糊的迭代次数以得到更好的效果）
private void OnRenderImage(RenderTexture src, RenderTexture dest)
{
      if (material != null)
      {
         int rtW = src.width/_DownSample;
         int rtH = src.height/_DownSample;
         RenderTexture buffer0 = RenderTexture.GetTemporary(rtW, rtH, 0);
         buffer0.filterMode = FilterMode.Bilinear;

         Graphics.Blit(src,buffer0);

         for (int i = 0; i < _Iterations; i++)
         {
            material.SetFloat(&#34;_BlurSize&#34;,1.0f + i * _BlurSpread);

            RenderTexture buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);
            //渲染垂直方向的Pass
            Graphics.Blit(src,buffer1,material,0);

            RenderTexture.ReleaseTemporary(buffer0);
            buffer0 = buffer1;
            buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);

            //渲染水平方向的Pass
            Graphics.Blit(src,buffer1,material,1);

            RenderTexture.ReleaseTemporary(buffer0);
            buffer0 = buffer1;
         }

         Graphics.Blit(buffer0,dest);
         RenderTexture.ReleaseTemporary(buffer0);
      }
      else
      {
         Graphics.Blit(src,dest);
      }
}
}
用来渲染后处理效果的Shader实现如下：
Shader &#34;Unlit/GaussianBlur&#34;
{
Properties
{
      _MainTex (&#34;Texture&#34;, 2D) = &#34;white&#34; {}
      _BlurSize (&#34;Blur Size&#34;, Float) = 1.0
}
SubShader
{
      CGINCLUDE

      #include &#34;UnityCG.cginc&#34;

      sampler2D _MainTex;
      float4 _MainTex_TexelSize;
      float _BlurSize;

      struct appdata
      {
         float4 vertex : POSITION;
         float2 uv : TEXCOORD0;
      };

      struct v2f
      {
         float4 pos : SV_POSITION;
         half2 uv[5] : TEXCOORD0;
      };

      //垂直方向的顶点着色器
      v2f vertBlurVertical(appdata v)
      {
         v2f o;
         o.pos = UnityObjectToClipPos(v.vertex);
         half2 uv = v.uv;

         o.uv[0] = uv;
         o.uv[1] = uv + float2(0.0, _MainTex_TexelSize.y * 1.0) * _BlurSize;
         o.uv[2] = uv + float2(0.0, _MainTex_TexelSize.y * -1.0) * _BlurSize;
         o.uv[3] = uv + float2(0.0, _MainTex_TexelSize.y * 2.0) * _BlurSize;
         o.uv[4] = uv + float2(0.0, _MainTex_TexelSize.y * -2.0) * _BlurSize;

         return o;
      }
      //水平方向的顶点着色器
      v2f vertBlurHorizontal(appdata v)
      {
         v2f o;
         o.pos = UnityObjectToClipPos(v.vertex);
         half2 uv = v.uv;

         o.uv[0] = uv;
         o.uv[1] = uv + float2( _MainTex_TexelSize.x * 1.0, 0.0) * _BlurSize;
         o.uv[2] = uv + float2( _MainTex_TexelSize.x * -1.0, 0.0) * _BlurSize;
         o.uv[3] = uv + float2( _MainTex_TexelSize.x * 2.0, 0.0) * _BlurSize;
         o.uv[4] = uv + float2( _MainTex_TexelSize.x * -2.0, 0.0) * _BlurSize;

         return o;
      }

      fixed4 fragBlur(v2f i) : SV_Target
      {
         //{0.0545, 0.2442, 0.4026, 0.2442, 0.0545} 高斯核，写成下边这样以提升性能
         float weight[3] = {0.4026, 0.2442, 0.0545};

         //根据高斯核计算五个点的采样之和
         fixed3 sum = tex2D(_MainTex,i.uv[0]).rgb * weight[0];

         for(int it = 1; it < 3; it++)
         {
            sum += tex2D(_MainTex,i.uv[it]).rgb * weight[it];
            sum += tex2D(_MainTex,i.uv[it*2]).rgb * weight[it];
         }
         return fixed4(sum,1.0);
      }

      ENDCG

      //后处理标配
      ZWrite Off
      ZTest Always
      Cull Off

      Pass
      {
         NAME &#34;GAUSSIAN_BLUR_VERTICAL&#34;

         CGPROGRAM
         #pragma vertex vertBlurVertical
         #pragma fragment fragBlur

         ENDCG
      }

      Pass
      {
         NAME &#34;GAUSSIAN_BLUR_HORIZONTAL&#34;

         CGPROGRAM
         #pragma vertex vertBlurHorizontal
         #pragma fragment fragBlur

         ENDCG
      }
}
Fallback Off
}
渲染结果如下：

此篇文章是在学习《Unity Shader入门精要》一书的笔记，加入了一些个人理解，如有错误之处，还请各位不吝赐教。

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Unity屏幕后处理（高斯模糊）

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