模糊组件（转）

转载自：Unity 的CommandBuffer基础_u012740992的专栏-CSDN博客_commandbuffer

原理：将需要模糊的UI单独添加一个摄像机和canvas，canvas下建一个background添加CommandBufferBlurRefraction组件用来显示模糊的背景，用commanderbuffer抓取屏幕并用模糊shader模糊，再将commanderbuffer添加到模糊像机外的所有相机上。

1，SeparableBlur.shader //(不需挂载目标) 作用：渲染模糊效果。
2，GlassWithoutGrab.shader //(糊透明玻璃镜体挂的着色器) 作用：等待输入模糊的抓屏纹理， 将自己的主纹理与抓屏输入纹理混合作为输出，得出模糊透明效果。
3，CommandBufferBlurRefraction.cs //(糊透明玻璃镜体挂的脚本) 作用：抓取当前屏幕纹理并用SeparableBlur.shader渲染出模糊纹理，将模糊纹理传给GlassWithoutGrab.shader混合。

using UnityEngine;
using UnityEngine.Rendering;
using System.Collections.Generic;

[ExecuteInEditMode]
public class CommandBufferBlurRefraction : MonoBehaviour
{
public Shader m_BlurShader;
private Material m_Material;

private Camera m_Cam;

// We'll want to add a command buffer on any camera that renders us,
// so have a dictionary of them.
private Dictionary<Camera,CommandBuffer> m_Cameras = new Dictionary<Camera,CommandBuffer>();

// Remove command buffers from all cameras we added into
private void Cleanup()
{
foreach (var cam in m_Cameras)
{
if (cam.Key)
{
cam.Key.RemoveCommandBuffer (CameraEvent.AfterSkybox, cam.Value);
}
}
m_Cameras.Clear();
Object.DestroyImmediate (m_Material);
}

public void OnEnable()
{
Cleanup();
}

public void OnDisable()
{
Cleanup();
}

// Whenever any camera will render us, add a command buffer to do the work on it
public void OnWillRenderObject()
{
var act = gameObject.activeInHierarchy && enabled;
if (!act)
{
Cleanup();
return;
}

var cam = Camera.current;
if (!cam)
return;

CommandBuffer buf = null;
// Did we already add the command buffer on this camera? Nothing to do then.
if (m_Cameras.ContainsKey(cam))
return;

if (!m_Material)
{
m_Material = new Material(m_BlurShader);
m_Material.hideFlags = HideFlags.HideAndDontSave;
}

buf = new CommandBuffer();
buf.name = "Grab screen and blur";
m_Cameras[cam] = buf;

// copy screen into temporary RT
//获取渲染纹理ID
int screenCopyID = Shader.PropertyToID("_ScreenCopyTexture");
//用screenCopyID标识，获取一个模板纹理。
buf.GetTemporaryRT (screenCopyID, -1, -1, 0, FilterMode.Bilinear);
//BuiltinRenderTextureType.CurrentActive也就是当前屏幕的纹理标识，将其赋值进screenCopyID标识的纹理。
buf.Blit (BuiltinRenderTextureType.CurrentActive, screenCopyID);

// get two smaller RTs
//获取2个模板纹理，后面将它们2的效果轮流混合。
int blurredID = Shader.PropertyToID("_Temp1");
int blurredID2 = Shader.PropertyToID("_Temp2");
buf.GetTemporaryRT (blurredID, -2, -2, 0, FilterMode.Bilinear);
buf.GetTemporaryRT (blurredID2, -2, -2, 0, FilterMode.Bilinear);

// downsample screen copy into smaller RT, release screen RT
//将抓屏纹理_ScreenCopyTexture采样填充到_Temp1后释放。
buf.Blit (screenCopyID, blurredID);
buf.ReleaseTemporaryRT (screenCopyID);

// horizontal blur
//修改SeparableBlur.shader的全局参数offsets，使其产生各个方向的模糊效果来叠加增强效果。
//（如果着色器不在 Properties模块中暴露某个参数，将使用全局属性）
buf.SetGlobalVector("offsets", new Vector4(2.0f/Screen.width,0,0,0));
//使用m_Material渲染blurredID结果赋值给blurredID2。
buf.Blit (blurredID, blurredID2, m_Material);
// vertical blur
buf.SetGlobalVector("offsets", new Vector4(0,2.0f/Screen.height,0,0));
buf.Blit (blurredID2, blurredID, m_Material);
// horizontal blur
buf.SetGlobalVector("offsets", new Vector4(4.0f/Screen.width,0,0,0));
buf.Blit (blurredID, blurredID2, m_Material);
// vertical blur
buf.SetGlobalVector("offsets", new Vector4(0,4.0f/Screen.height,0,0));
buf.Blit (blurredID2, blurredID, m_Material);

//得到透明效果纹理后，赋值给GlassWithoutGrab.shader的_GrabBlurTexture混合得出模糊透明。
buf.SetGlobalTexture("_GrabBlurTexture", blurredID);

cam.AddCommandBuffer (CameraEvent.AfterSkybox, buf);
}
}

Shader "Hidden/SeparableGlassBlur" {
Properties {
_MainTex ("Base (RGB)", 2D) = "" {}
}

CGINCLUDE

#include "UnityCG.cginc"

struct v2f {
float4 pos : POSITION;
float2 uv : TEXCOORD0;

float4 uv01 : TEXCOORD1;
float4 uv23 : TEXCOORD2;
float4 uv45 : TEXCOORD3;
};

float4 offsets;

sampler2D _MainTex;
//偏移定点uv，使其读取到周围颜色值进行混合。
v2f vert (appdata_img v) {
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);

o.uv.xy = v.texcoord.xy;

o.uv01 = v.texcoord.xyxy + offsets.xyxy * float4(1,1, -1,-1);
o.uv23 = v.texcoord.xyxy + offsets.xyxy * float4(1,1, -1,-1) * 2.0;
o.uv45 = v.texcoord.xyxy + offsets.xyxy * float4(1,1, -1,-1) * 3.0;

return o;
}
//混合颜色值。
half4 frag (v2f i) : COLOR {
half4 color = float4 (0,0,0,0);

color += 0.40 * tex2D (_MainTex, i.uv);
color += 0.15 * tex2D (_MainTex, i.uv01.xy);
color += 0.15 * tex2D (_MainTex, i.uv01.zw);
color += 0.10 * tex2D (_MainTex, i.uv23.xy);
color += 0.10 * tex2D (_MainTex, i.uv23.zw);
color += 0.05 * tex2D (_MainTex, i.uv45.xy);
color += 0.05 * tex2D (_MainTex, i.uv45.zw);

return color;
}

ENDCG

Subshader {
Pass {
ZTest Always Cull Off ZWrite Off
Fog { Mode off }

CGPROGRAM
#pragma fragmentoption ARB_precision_hint_fastest
#pragma vertex vert
#pragma fragment frag
ENDCG
}
}

Fallback off

}

Shader "FX/Glass/Stained BumpDistort (no grab)" {
Properties {
_BumpAmt ("Distortion", range (0,64)) = 10
_TintAmt ("Tint Amount", Range(0,1)) = 0.1
_MainTex ("Tint Color (RGB)", 2D) = "white" {}
_BumpMap ("Normalmap", 2D) = "bump" {}
}

Category {

// We must be transparent, so other objects are drawn before this one.
Tags { "Queue"="Transparent" "RenderType"="Opaque" }

SubShader {

Pass {
Name "BASE"
Tags { "LightMode" = "Always" }

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_fog
#include "UnityCG.cginc"

struct appdata_t {
float4 vertex : POSITION;
float2 texcoord: TEXCOORD0;
};

struct v2f {
float4 vertex : POSITION;
float4 uvgrab : TEXCOORD0;
float2 uvbump : TEXCOORD1;
float2 uvmain : TEXCOORD2;
UNITY_FOG_COORDS(3)
};

float _BumpAmt;
half _TintAmt;
float4 _BumpMap_ST;
float4 _MainTex_ST;

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
//将顶点裁剪空间下的坐标，计算NDC空间上的位置后，映射到模糊纹理的uv。
o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;
o.uvgrab.zw = o.vertex.zw;
o.uvbump = TRANSFORM_TEX( v.texcoord, _BumpMap );
o.uvmain = TRANSFORM_TEX( v.texcoord, _MainTex );
UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}
//抓屏得到的模糊纹理会赋值到此。(因为Properties没有定义_GrabBlurTexture，所以默认使用全局的参数)
sampler2D _GrabBlurTexture;
float4 _GrabBlurTexture_TexelSize;
sampler2D _BumpMap;
sampler2D _MainTex;

half4 frag (v2f i) : SV_Target
{
// calculate perturbed coordinates
// we could optimize this by just reading the x & y without reconstructing the Z
half2 bump = UnpackNormal(tex2D( _BumpMap, i.uvbump )).rg;
float2 offset = bump * _BumpAmt * _GrabBlurTexture_TexelSize.xy;
i.uvgrab.xy = offset * i.uvgrab.z + i.uvgrab.xy;

//对模糊纹理采样
half4 col = tex2Dproj (_GrabBlurTexture, UNITY_PROJ_COORD(i.uvgrab));
half4 tint = tex2D(_MainTex, i.uvmain);
//模糊纹理与主纹理混合得出模糊透明效果
col = lerp (col, tint, _TintAmt);
UNITY_APPLY_FOG(i.fogCoord, col);
return col;
}
ENDCG
}
}

}

}