UnityShader屏幕后处理-Bloom效果(朦胧模糊)

原理：1 取出图片中比较亮(饱和度比较高、远离灰色)的一部分图

2 对1中的图进行高斯模糊的到新的图

3 将2中的图与原图色彩相加

1 取出图片中比较亮的的区域

C#

material.SetFloat("_LuminanceThreshold", luminanceThreshold);

int rtW = src.width/downSample;
int rtH = src.height/downSample;

RenderTexture buffer0 = RenderTexture.GetTemporary(rtW, rtH, 0);
buffer0.filterMode = FilterMode.Bilinear;

Graphics.Blit(src, buffer0, material, 0);

shader

v2f vertExtractBright(appdata_img v) {
v2f o;

o.pos = UnityObjectToClipPos(v.vertex);

o.uv = v.texcoord;

return o;
}

fixed luminance(fixed4 color) {
return  0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b;
}

fixed4 fragExtractBright(v2f i) : SV_Target {
fixed4 c = tex2D(_MainTex, i.uv);
fixed val = clamp(luminance(c) - _LuminanceThreshold, 0.0, 1.0);

return c * val;
}

2 对1中的图进行高斯模糊

C#

for (int i = 0; i < iterations; i++) {
material.SetFloat("_BlurSize", 1.0f + i * blurSpread);

RenderTexture buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);

// Render the vertical pass
Graphics.Blit(buffer0, buffer1, material, 1);

RenderTexture.ReleaseTemporary(buffer0);
buffer0 = buffer1;
buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);

// Render the horizontal pass
Graphics.Blit(buffer0, buffer1, material, 2);

RenderTexture.ReleaseTemporary(buffer0);
buffer0 = buffer1;
}

shader

参考上一篇博客高斯模糊

3 将2的到的RenderTexture与原图颜色相加

C#

material.SetTexture ("_Bloom", buffer0);
Graphics.Blit (src, dest, material, 3);

shader

v2fBloom vertBloom(appdata_img v) {
v2fBloom o;

o.pos = UnityObjectToClipPos (v.vertex);
o.uv.xy = v.texcoord;
o.uv.zw = v.texcoord;

#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0.0)
o.uv.w = 1.0 - o.uv.w;
#endif

return o;
}

fixed4 fragBloom(v2fBloom i) : SV_Target {
return tex2D(_MainTex, i.uv.xy) + tex2D(_Bloom, i.uv.zw);
}

里面使用UNITY_UV_STARTS_AT_TOP来判断是否是DX平台并且开启了抗锯齿效果(Edit-ProjectSetting-Quality-AntiAliasing)….然而我还没遇到过。。。

4代码

Bloom.cs

using UnityEngine;
using System.Collections;

public class Bloom : PostEffectsBase {

public Shader bloomShader;
private Material bloomMaterial = null;
public Material material {
get {
bloomMaterial = CheckShaderAndCreateMaterial(bloomShader, bloomMaterial);
return bloomMaterial;
}
}

// Blur iterations - larger number means more blur.
[Range(0, 4)]
public int iterations = 3;

// Blur spread for each iteration - larger value means more blur
[Range(0f, 3.0f)]
public float blurSpread = 0.6f;

[Range(1, 8)]
public int downSample = 2;

[Range(0.0f, 4.0f)]
public float luminanceThreshold = 0.6f;

void OnRenderImage (RenderTexture src, RenderTexture dest) {
if (material != null) {
material.SetFloat("_LuminanceThreshold", luminanceThreshold);

int rtW = src.width/downSample;
int rtH = src.height/downSample;

RenderTexture buffer0 = RenderTexture.GetTemporary(rtW, rtH, 0);
buffer0.filterMode = FilterMode.Bilinear;

Graphics.Blit(src, buffer0, material, 0);

for (int i = 0; i < iterations; i++) {
material.SetFloat("_BlurSize", 1.0f + i * blurSpread);

RenderTexture buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);

// Render the vertical pass
Graphics.Blit(buffer0, buffer1, material, 1);

RenderTexture.ReleaseTemporary(buffer0);
buffer0 = buffer1;
buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);

// Render the horizontal pass
Graphics.Blit(buffer0, buffer1, material, 2);

RenderTexture.ReleaseTemporary(buffer0);
buffer0 = buffer1;
}

material.SetTexture ("_Bloom", buffer0);
Graphics.Blit (src, dest, material, 3);

RenderTexture.ReleaseTemporary(buffer0);
} else {
Graphics.Blit(src, dest);
}
}
}

PostEffectsBase.cs

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

[ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
public class PostEffectsBase : MonoBehaviour {

protected bool CheckSupport() {
if (SystemInfo.supportsImageEffects == false) {
Debug.LogWarning("This platform does not support image effects.");
return false;
}

return true;
}

protected void NotSupported() {
enabled = false;
}

protected void CheckResources() {
bool isSupported = CheckSupport();

if (isSupported == false) {
NotSupported();
}
}

protected void Start() {
CheckResources();
}

// Called when need to create the material used by this effect
protected Material CheckShaderAndCreateMaterial(Shader shader, Material material) {
if (shader == null) {
return null;
}

if (shader.isSupported && material && material.shader == shader)
return material;

if (!shader.isSupported) {
return null;
}
else {
material = new Material(shader);
material.hideFlags = HideFlags.DontSave;
if (material)
return material;
else
return null;
}
}
}

Bloom.shader

Shader "Custom/Bloom" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_Bloom ("Bloom (RGB)", 2D) = "black" {}
_LuminanceThreshold ("Luminance Threshold", Float) = 0.5
_BlurSize ("Blur Size", Float) = 1.0
}
SubShader {
CGINCLUDE

#include "UnityCG.cginc"

sampler2D _MainTex;
half4 _MainTex_TexelSize;
sampler2D _Bloom;
float _LuminanceThreshold;
float _BlurSize;

struct v2f {
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
};

v2f vertExtractBright(appdata_img v) {
v2f o;

o.pos = UnityObjectToClipPos(v.vertex);

o.uv = v.texcoord;

return o;
}

fixed luminance(fixed4 color) {
return  0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b;
}

fixed4 fragExtractBright(v2f i) : SV_Target {
fixed4 c = tex2D(_MainTex, i.uv);
fixed val = clamp(luminance(c) - _LuminanceThreshold, 0.0, 1.0);

return c * val;
}

struct v2fBloom {
float4 pos : SV_POSITION;
half4 uv : TEXCOORD0;
};

v2fBloom vertBloom(appdata_img v) {
v2fBloom o;

o.pos = UnityObjectToClipPos (v.vertex);
o.uv.xy = v.texcoord;
o.uv.zw = v.texcoord;

#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0.0)
o.uv.w = 1.0 - o.uv.w;
#endif

return o;
}

fixed4 fragBloom(v2fBloom i) : SV_Target {
return tex2D(_MainTex, i.uv.xy) + tex2D(_Bloom, i.uv.zw);
}

ENDCG

ZTest Always Cull Off ZWrite Off

Pass {
CGPROGRAM
#pragma vertex vertExtractBright
#pragma fragment fragExtractBright

ENDCG
}

UsePass "Custom/Gaussian Blur/GAUSSIAN_BLUR_VERTICAL"

UsePass "Custom/Gaussian Blur/GAUSSIAN_BLUR_HORIZONTAL"

Pass {
CGPROGRAM
#pragma vertex vertBloom
#pragma fragment fragBloom

ENDCG
}
}
FallBack Off
}