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 lookconst float fSampleDist;const float fSampleStrength; // some sample positionsfloat 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 screen float2 dir = 0.5 - texCoord; // calculate the distance to the center of the screen float 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 version float4 color = tex2D(Texture0, texCoord); float4 sum = color; // take 10 additional blur samples in the direction towards // the center of the screen for (int i = 0; i < 10; ++i) { sum += tex2D(Texture0, texCoord + dir * samples[i] * fSampleDist); } // we have taken eleven samples sum /= 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 pixels return 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 Off Fog { 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:
