径向模糊shader

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 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：

按 Ctrl+C 复制代码

//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: