（转）径向模糊效果shader

转自：http://blog.csdn.net/xoyojank/article/details/5146297

最先在这里看到:http://www.gamerendering.com/2008/12/20/radial-blur-filter/

这效果在鬼泣4中切换场景时见过, 极品飞车12的运动模糊也有这种感觉.

原理:

确定一个中心点(如0.5, 0.5), 跟当前像素连一条线. 以当前像素为中心, 在线上的附近像素进行采样, 最后取一下平均值.

代码翻译成HLSL:

// This texture should hold the image to blur.
sampler2D Texture0;// some const, tweak for best look
const float fSampleDist;
const float fSampleStrength; // some sample positions
float samples[10] = 
{-0.08,-0.05,-0.03,-0.02,-0.01,0.01,0.02,0.03,0.05,0.08
};float4 ps_main( float2 texCoord  : TEXCOORD0 ) : COLOR
{// 0.5,0.5 is the center of the screen// so substracting uv from it will result in// a vector pointing to the middle of the screenfloat2 dir = 0.5 - texCoord;// calculate the distance to the center of the screenfloat dist = length(dir);// normalize the direction (reuse the distance)dir /= dist;// this is the original colour of this pixel// using only this would result in a nonblurred versionfloat4 color = tex2D(Texture0, texCoord);float4 sum = color;// take 10 additional blur samples in the direction towards// the center of the screenfor (int i = 0; i < 10; ++i){sum += tex2D(Texture0, texCoord + dir * samples[i] * fSampleDist);}// we have taken eleven samplessum /= 11.0;// weighten the blur effect with the distance to the// center of the screen ( further out is blurred more)float t = saturate(dist * fSampleStrength);//Blend the original color with the averaged pixelsreturn lerp(color, sum, t);
}

Unity shaderLab：

//径向模糊后处理
Shader "RadialBlur" {Properties {_MainTex ("Base (RGB)", 2D) = "white" {}_fSampleDist("SampleDist", Float) = 1 //采样距离_fSampleStrength("SampleStrength", Float) = 2.2 //采样力度
         }SubShader {Pass {               ZTest Always Cull Off ZWrite OffFog { Mode off }  CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"struct appdata_t {float4 vertex : POSITION;float2 texcoord : TEXCOORD;};struct v2f {float4 vertex : POSITION;float2 texcoord : TEXCOORD;};float4 _MainTex_ST;v2f vert (appdata_t v){v2f o;o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);return o;}sampler2D _MainTex;float _fSampleDist;float _fSampleStrength;// some sample positions  static const float samples[6] =   {   -0.05,  -0.03,    -0.01,  0.01,    0.03,  0.05,  }; half4 frag (v2f i) : SV_Target{//0.5,0.5屏幕中心float2 dir = float2(0.5, 0.5) - i.texcoord;//从采样中心到uv的方向向量float2 texcoord = i.texcoord;float dist = length(dir);  dir = normalize(dir); float4 color = tex2D(_MainTex, texcoord);  float4 sum = color;//    6次采样for (int i = 0; i < 6; ++i)  {  sum += tex2D(_MainTex, texcoord + dir * samples[i] * _fSampleDist);    }  //求均值sum /= 7.0f;  //越离采样中心近的地方，越不模糊float t = saturate(dist * _fSampleStrength);  //插值return lerp(color, sum, t);}ENDCG }} Fallback off}

两个参数, 动态调整的话可以产生极品飞车12那种速度感(也算是第一人称运动模糊的简单实现吧).

这是RM里的效果: