UnityShader高级篇——Bloom效果

1.将此脚本挂在相机上

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

public class Bloom : PostEffectsBase
{

    public Shader BloomShader;
    private Material _bloomMaterial = null;

    public Material Material
    {
        get
        {
            _bloomMaterial = CheckShaderAndCreateMaterial(BloomShader, _bloomMaterial);
            return _bloomMaterial;
        }
    }

    //Bloom是建立在高斯模糊基础上的，所以参数基本与高斯模糊一样
    //模糊迭代次数
    [Range(0,4)] public int Iterations = 3;
    //模糊范围
    [Range(0.2f, 3.0f)] public float BlurSperad = 0.6f;
    //缩放系数
    [Range(1, 8)] public int DownSample = 2;
    //亮度阈值，控制提取较亮区域时使用的阈值大小
    //一般情况下图像的亮度值不会超过1，但是如果开启了HDR，硬件会允许颜色值被存储在一个更高精度范围的缓冲中，此时可能会超过1，所以范围定在0-4
    [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;

            //使用Shader中的第一个Pass提取图像中较亮的区域
            Graphics.Blit(src, buffer0, Material, 0);

            //高斯模糊迭代处理
            for (int i = 0; i < Iterations; i++)
            {
                Material.SetFloat("_BlurSize", 1.0f + i * BlurSperad);
                RenderTexture buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);
                //使用第二个Pass,渲染竖直滤波
                Graphics.Blit(buffer0, buffer1,Material,1);
                RenderTexture.ReleaseTemporary(buffer0);
                buffer0 = buffer1;
                buffer1 = RenderTexture.GetTemporary(rtW, rtH, 0);
                //使用第三个Pass，渲染水平滤波
                Graphics.Blit(buffer0, buffer1, Material, 2);
                RenderTexture.ReleaseTemporary(buffer0);
                buffer0 = buffer1;
            }

            //把材质传递给材质中的Bloom纹理属性
            Material.SetTexture("_Bloom", buffer0);
            //使用第四个Pass，将原图与材质进行混合,并输出最终结果
            Graphics.Blit(src, dest, Material, 3);
            RenderTexture.ReleaseTemporary(buffer0);
        }
        else
        {
            Graphics.Blit(src, dest);
        }
    }

}

2.将此shader赋值给脚本

Shader "Unity Shaders Book/Chapter 12/Bloom"
{
	Properties
	{
		_MainTex ("Base (RGB)", 2D) = "white" {}
	    //高斯模糊的较亮区域
	    _Bloom ("Bloom (RGB)", 2D) = "black"{}
		//提取较亮区域的阈值
		_LuminanceThreshold("Luminance Threshold", Float) = 0.5
		//控制不同迭代之间高斯模糊的模糊区域范围
		_BlurSize("Blur Size", Float) = 1.0

	}
	SubShader
	{
		CGINCLUDE
		#include "UnityCG.cginc"

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

		//定义提取较亮区域需要使用的顶点着色器和片元着色器
		struct v2f {
			float4 pos : SV_POSITION;
			half2 uv : TEXCOORD0;
		};

		//顶点着色器与之前相同
		v2f vertExtractBright(appdata_img v) {
			v2f o;
			o.pos = UnityObjectToClipPos(v.vertex);
			o.uv = v.texcoord;
			return o;
		}

		//亮度值采样
		fixed luminance(fixed4 color) {
			return 0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b;
		}

		//片元着色器，得到亮部区域
		fixed4 fragExtractBright(v2f i) : SV_Target
		{
			fixed4 c = tex2D(_MainTex, i.uv);
			//将亮度值减去阈值并截取到0-1范围
			fixed val = clamp(luminance(c) - _LuminanceThreshold, 0.0, 1.0);
			//将该值与原像素值相乘，得到亮部区域
			return c * val;
		}

		//定义混合亮部区域与原图像时使用的顶点着色器和片元着色器
		struct v2fBloom {
			float4 pos : SV_POSITION;
			//使用half4同时存储_MainTex与_Bloom的坐标
			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;
			
			//平台差异化处理
			//判断是否时DirectX平台(uv从顶部开始)
			#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
		{
			//把两张纹理的采样结果相加混合
			return tex2D(_MainTex, i.uv.xy) + tex2D(_Bloom,i.uv.zw);
		}
			
		ENDCG

		//定义Bloom效果需要的4个Pass
		
		ZTest Always Cull Off Zwrite Off

		Pass
		{
			CGPROGRAM
			#pragma vertex vertExtractBright
			#pragma fragment fragExtractBright		
			ENDCG
		}

		//使用在高斯模糊中定义好的两个Pass
		UsePass"UnityShaderBook/Chapter12/GaussianBlur/GAUSSIAN_BLUR_VERTICAL"

		UsePass"UnityShaderBook/Chapter12/GaussianBlur/GAUSSIAN_BLUR_HORIZONTAL"

		Pass
		{
			CGPROGRAM
			#pragma vertex vertBloom
			#pragma fragment fragBloom	
			ENDCG
		}
	}
		Fallback Off
}