C for Graphic：径向模糊

      最近要做一系列特效需求，顺便记录一下。
      径向模糊（也叫辐射模糊）：一种由内向外发散的模糊的效果
在这里插入图片描述
      原理：获取中心点（centeruv）到当前像素（pixeluv）的朝向法向量（ndir），pixeluv沿着ndir进行向前向后的像素颜色采样，并叠加到当前像素颜色（pixelcolor）
      和以前聊过的高斯滤器模糊有点类似，核心都是将其他像素颜色叠加到当前像素颜色，无非叠加的计算规则不同
      画个图：
在这里插入图片描述       以pixeluv为起点，ndir为朝向，向外、向内、或两端同时采样颜色进行叠加，为了保证叠加后亮度的统一，除以采样次数进行衰减即可

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class RadialBlurScreenEffect : MonoBehaviour
{public Material mat;[Range(1, 5)]public int downSample = 2;private int downWidth;private int downHeight;void Start(){downWidth = Screen.width / downSample;downHeight = Screen.height / downSample;}private void Update(){if (Input.GetMouseButton(1)){Vector2 spos = Input.mousePosition;Vector2 uv = new Vector2(spos.x / Screen.width, spos.y / Screen.height);mat.SetVector("_CenterUV", uv);}}private void OnRenderImage(RenderTexture source, RenderTexture destination){if (mat != null){//为了性能考虑，先降采样RenderTexture downRt = RenderTexture.GetTemporary(downWidth, downHeight, 0, RenderTextureFormat.ARGB32);Graphics.Blit(source, downRt);Graphics.Blit(downRt, destination, mat);RenderTexture.ReleaseTemporary(downRt);}else{Graphics.Blit(source, destination);}}
}

后处理控制器，降采样提升效率

Shader "RadialBlur/RadialBlurImageEffectShader"
{Properties{_MainTex ("Texture", 2D) = "white" {}_CenterUV("Center UV",vector) = (0.5,0.5,0,0)_SampleCount("Sample Count",Range(5,30)) = 10_SampleDistance("Sample Distance",Range(0.005,0.03)) = 0.01[Enum(InOut,1,In,2,Out,3)]_InOut("In Out Type",int) = 0}SubShader{// No culling or depthCull Off ZWrite Off ZTest AlwaysPass{CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"struct appdata{float4 vertex : POSITION;float2 uv : TEXCOORD0;};struct v2f{float2 uv : TEXCOORD0;float4 vertex : SV_POSITION;float2 ndir : TEXCOORD1;};float2 _CenterUV;int _SampleCount;float _SampleDistance;int _InOut;v2f vert (appdata v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.uv = v.uv;o.ndir = normalize(o.uv-_CenterUV.xy);return o;}sampler2D _MainTex;fixed4 frag (v2f i) : SV_Target{fixed4 col = fixed4(0,0,0,0);fixed2 dir = i.ndir;if(_InOut == 1){int halfsample = _SampleCount/2;for(int x=0;x<_SampleCount;x++){int offset = x-halfsample;col += (tex2D(_MainTex,i.uv+dir*(offset*_SampleDistance))/(float)_SampleCount);}}else if(_InOut == 2){for(int x=0;x<_SampleCount;x++){col += (tex2D(_MainTex,i.uv+dir*(x*_SampleDistance))/(float)_SampleCount);}}else if(_InOut == 3){for(int x=0;x<_SampleCount;x++){col += (tex2D(_MainTex,i.uv-dir*(x*_SampleDistance))/(float)_SampleCount);}}return col;}ENDCG}}
}