unity之模糊背景（带你欣赏女人的朦胧美）

最近项目用到了模糊背景效果。实现方法为：shader。代码来自百度。接下来给大家介绍一下模糊背景的实现过程。首先你需要一个先人已经写好的shader（当然，如果你有能力，也可以自己实现！）
没有的可以通过以下链接下载材质球和对应的shader。
模糊背景shader
模糊背景材质球
shader如下：

Shader "FT/Blur/Back"
{
	Properties
	{
		_Color ("Main Color", Color) = (1,1,1,1)
        _Size ("Size", Range(0, 20)) = 1
	}
	Category {  
  
        // We must be transparent, so other objects are drawn before this one.  
        Tags { 
			"Queue"="Transparent" 
			"IgnoreProjector"="True" 
			"RenderType"="Transparent"
			"PreviewType" = "Plane"
			"CanUseSpriteAtlas" = "True"
		}  
  
  
        SubShader {  
  
            // Horizontal blur  
            GrabPass 
			{                      
                Tags { "LightMode" = "Always" }  
            }  
            Pass {
                Tags { "LightMode" = "Always" }  

                Name "BackBlurHor"
                CGPROGRAM  
                #pragma vertex vert  
                #pragma fragment frag  
                #pragma fragmentoption ARB_precision_hint_fastest  
                #include "UnityCG.cginc"  
  
                struct appdata_t {  
                    float4 vertex : POSITION;  
                    float2 texcoord : TEXCOORD0;
					float4 color    : COLOR;
                };  
  
                struct v2f {  
                    float4 vertex : POSITION;  
                    float4 uvgrab : TEXCOORD0;
					float4 color    : COLOR;
                };
  
                v2f vert (appdata_t v) {  
                    v2f o; 
                    o.vertex = UnityObjectToClipPos(v.vertex);  
                    #if UNITY_UV_STARTS_AT_TOP  
                    float scale = -1.0;  
                    #else  
                    float scale = 1.0;  
                    #endif  
                    o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;  
                    o.uvgrab.zw = o.vertex.zw;  

					o.color = v.color;
                    return o;  
                }  
  
                sampler2D _GrabTexture;  
                float4 _GrabTexture_TexelSize;
			    float4 _MainTex_TexelSize;
                float _Size;
                uniform float4 _Color;

                half4 GrabPixel(v2f i, float weight, float kernel){
                    kernel = sign(sign(abs(i.uvgrab.x)) + sign(abs(i.uvgrab.y))) * kernel;
					return tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x + _GrabTexture_TexelSize.x * kernel * _Size, i.uvgrab.y, i.uvgrab.z, i.uvgrab.w))) * weight;
                }
                half4 frag( v2f i ) : COLOR {  
                 	half4 sum = half4(0,0,0,0);
                    sum += GrabPixel(i, 0.05, -4.0);
                    sum += GrabPixel(i, 0.09, -3.0);
                    sum += GrabPixel(i, 0.12, -2.0);
                    sum += GrabPixel(i, 0.15, -1.0);
                    sum += GrabPixel(i, 0.18,  0.0);
                    sum += GrabPixel(i, 0.15, +1.0);
                    sum += GrabPixel(i, 0.12, +2.0);
                    sum += GrabPixel(i, 0.09, +3.0);
                    sum += GrabPixel(i, 0.05, +4.0);

                    float4 col5 = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
					fixed decayFactor = sign(sign(abs(i.uvgrab.x)) + sign(abs(i.uvgrab.y)));
					sum = lerp(col5, sum, decayFactor) * i.color * _Color;
  
                    return sum;  
                }  
                ENDCG  
            }  
			
            // Vertical blur  
            GrabPass {                          
                Tags { "LightMode" = "Always" }  
            }  
            Pass {  
                Tags { "LightMode" = "Always" }

                Name "BackBlurVer"
                CGPROGRAM  
                #pragma vertex vert  
                #pragma fragment frag  
                #pragma fragmentoption ARB_precision_hint_fastest  
                #include "UnityCG.cginc"  
  
                struct appdata_t {  
                    float4 vertex : POSITION;  
                    float2 texcoord: TEXCOORD0;  
					float4 color    : COLOR;
                };  
  
                struct v2f {  
                    float4 vertex : POSITION;  
                    float4 uvgrab : TEXCOORD0;  
					float4 color    : COLOR;
                };  
  
                v2f vert (appdata_t v) {  
                    v2f o;  
                    o.vertex = UnityObjectToClipPos(v.vertex);  
                    #if UNITY_UV_STARTS_AT_TOP  
                    float scale = -1.0;  
                    #else  
                    float scale = 1.0;  
                    #endif  
                    o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;  
                    o.uvgrab.zw = o.vertex.zw;  

					o.color = v.color;
                    return o;  
                }  
  
                sampler2D _GrabTexture;  
                float4 _GrabTexture_TexelSize;  
                float _Size;
                uniform float4 _Color;

                half4 GrabPixel(v2f i, float weight, float kernel){
					kernel = sign(sign(abs(i.uvgrab.x)) + sign(abs(i.uvgrab.y))) * kernel;
                    return tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x, i.uvgrab.y + _GrabTexture_TexelSize.y * kernel * _Size, i.uvgrab.z, i.uvgrab.w))) * weight;
                }
  
                half4 frag( v2f i ) : COLOR
				{
                    half4 sum = half4(0,0,0,0);  
                    sum += GrabPixel(i, 0.05, -4.0);
                    sum += GrabPixel(i, 0.09, -3.0);
                    sum += GrabPixel(i, 0.12, -2.0);
                    sum += GrabPixel(i, 0.15, -1.0);
                    sum += GrabPixel(i, 0.18,  0.0);
                    sum += GrabPixel(i, 0.15, +1.0);
                    sum += GrabPixel(i, 0.12, +2.0);
                    sum += GrabPixel(i, 0.09, +3.0);
                    sum += GrabPixel(i, 0.05, +4.0);

					float4 col5 = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
					fixed decayFactor = sign(sign(abs(i.uvgrab.x)) + sign(abs(i.uvgrab.y)));
					sum = lerp(col5, sum, decayFactor) * i.color * _Color;
  
                    return sum;  
                }  
                ENDCG  
            }
        }
	}
}

unity中使用方法：
为工程导入下载的材质球和shader
通常我们新建Material文件夹存放材质球

创建Shader文件夹存放shader代码

新建背景Image，命名为bg，并为其赋上指定的图片资源，如下：

新建模糊材质背景Image，命名为mask，SourceImage指定任意值即可；Material指定下载的材质球

效果如下：

调节材质球的Size可以调节模糊程度。值越大，效果越模糊。
在这里插入图片描述

将size值拉到5效果如下：