UnityShader 屏幕特效 模糊

1. 上一篇文章写了屏幕特效必须的几个要素，这边通过一个 脚本继承与PostEffectsBase .以及通过shader 交互实现屏幕模糊特效。

2. 下面通过添加在摄像机，引用3的shader。

using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
public class Test : PostEffectsBase {

public Shader edgeDetectShader;
private Material edgeDetectMaterial = null;
public Material material
    {
get
        {
            edgeDetectMaterial = CheckShaderAndCreateMaterial(edgeDetectShader, edgeDetectMaterial);
return edgeDetectMaterial;
        }
    }

    [Range(0.0f, 1.0f)]
public float Parameter = 0.0f;

//类似Update,也是会不断通过输入，输出结果
void OnRenderImage(RenderTexture src, RenderTexture dest)
    {
if (material != null)
        {
            material.SetFloat("_BlurAmount", Parameter);
            Graphics.Blit(src, dest, material);
        }
else
        {
            Graphics.Blit(src, dest);
        }
    }
}

3.下面Shader

Shader "Futile/Blur"
{
    Properties
    {
        _MainTex("Base (RGB) Trans (A)", 2D) = "white" {}
    _Color("Main Color", Color) = (0.2,0,1,1.5)
        _BlurAmount("Blur Amount", Range(0,02)) = 0.0005
    }

    Category
    {
        Tags{ "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Opaque"  }
        ZWrite Off
        //Alphatest Greater 0
        Cull Off

    SubShader
    {
        Pass
    {

        CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
#pragma profileoption NumTemps=64
        float4 _Color;
    sampler2D _MainTex;
    float _BlurAmount;

    struct v2f {
        float4  pos : SV_POSITION;
        float2  uv : TEXCOORD0;
    };

    float4 _MainTex_ST;

    v2f vert(appdata_base v)
    {
        v2f o;
        o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
        o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
        return o;
    }

    half4 frag(v2f i) : COLOR
    {
        half4 texcol = half4(0,0,0,0);
        float remaining = 1.0f;
        float coef = 1.0;
        float fI = 0;
        for (int j = 0; j < 3; j++) {
            fI++;
            coef *= 0.32;
            texcol += tex2D(_MainTex, float2(i.uv.x, i.uv.y - fI * _BlurAmount)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x - fI * _BlurAmount, i.uv.y)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x + fI * _BlurAmount, i.uv.y)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x, i.uv.y + fI * _BlurAmount)) * coef;

            remaining -= 4 * coef;
        }
        //return texcol;

        texcol += tex2D(_MainTex, float2(i.uv.x, i.uv.y)) * remaining;

        return texcol;
    }
        ENDCG



    }
    }
    }
}

4.简单介绍Category ：就是同一个Shader，如果下面有多个Shader的话，都会套用下面这一套

    Tags{ "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Opaque" }
    ZWrite Off
    //Alphatest Greater 0
    Cull Off

5.简单讲一下这个算法，这个通过在片元着色器进行上下左右进行像素微偏移

for (int j = 0; j < 3; j++) {
            fI++;
            coef *= 0.32;
            texcol += tex2D(_MainTex, float2(i.uv.x, i.uv.y - fI * _BlurAmount)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x - fI * _BlurAmount, i.uv.y)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x + fI * _BlurAmount, i.uv.y)) * coef;
            texcol += tex2D(_MainTex, float2(i.uv.x, i.uv.y + fI * _BlurAmount)) * coef;

            remaining -= 4 * coef;
        }

原图

模糊图，通过调参数Parameter

这边的Remaining为了 在下面保证迭代后基数为1。这样不会影响原本图像的亮度。比如这边基数默认设置10。就会锐化图像

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总结：
这边计算可以在顶点v2f vert(appdata_base v)里面计算，这样一位顶点计算量数比片元着色器计算更少。