Unity Shader总结（十二）——屏幕后处理

建立屏幕后处理脚本

首先创建脚本检查当前脚本是否支持，绑定在摄像机上；后面的屏幕特效继承该类即可；

using UnityEngine;
using System.Collections;

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

	// Called when start
	//检查各种资源和条件是否满足
	protected void CheckResources() {
   
		bool isSupported = CheckSupport();
		
		if (isSupported == false) {
   
			NotSupported();
		}
	}

	// Called in CheckResources to check support on this platform
	protected bool CheckSupport() {
   
		if (SystemInfo.supportsImageEffects == false || SystemInfo.supportsRenderTextures == false) {
   
			Debug.LogWarning("This platform does not support image effects or render textures.");
			return false;
		}
		
		return true;
	}

	// Called when the platform doesn't support this effect
	protected void NotSupported() {
   
		enabled = false;
	}
	
	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;
		}
	}
}

调整屏幕亮度、饱和度和对比度

该脚本给摄像机

using UnityEngine;
using System.Collections;

public class BrightnessSaturationAndContrast : PostEffectsBase {
   

	public Shader briSatConShader;
	private Material briSatConMaterial;
	public Material material {
     
		get {
   
			briSatConMaterial = CheckShaderAndCreateMaterial(briSatConShader, briSatConMaterial);
			return briSatConMaterial;
		}  
	}

	[Range(0.0f, 3.0f)]
	public float brightness = 1.0f;

	[Range(0.0f, 3.0f)]
	public float saturation = 1.0f;

	[Range(0.0f, 3.0f)]
	public float contrast = 1.0f;
	//OnRenderImage得到当前屏幕图像，利用Graphics.Blit处理后给RenderTexture
	void OnRenderImage(RenderTexture src, RenderTexture dest) {
   
		if (material != null) {
   
			material.SetFloat("_Brightness", brightness);
			material.SetFloat("_Saturation", saturation);
			material.SetFloat("_Contrast", contrast);

			Graphics.Blit(src, dest, material);
		} else {
   
			Graphics.Blit(src, dest);
		}
	}
}

把该shader拖到脚本属性中

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unity Shaders Book/Chapter 12/Brightness Saturation And Contrast" {
   
	Properties {
   
		_MainTex ("Base (RGB)", 2D) = "white" {
   }
		_Brightness ("Brightness", Float) = 1
		_Saturation("Saturation", Float) = 1
		_Contrast("Contrast", Float) = 1
	}
	SubShader {
   
		Pass {
     
		//防止对其他物体产生影响，屏幕后处理相当于绘制一个和屏幕相同大小的四边形面片
			ZTest Always Cull Off ZWrite Off
			
			CGPROGRAM  
			#pragma vertex vert  
			#pragma fragment frag  
			  
			#include "UnityCG.cginc"  
			  
			sampler2D _MainTex;  
			half _Brightness;
			half _Saturation;
			half _Contrast;
			  
			struct v2f {
   
				float4 pos : SV_POSITION;
				half2 uv: TEXCOORD0;
			};
			  
			v2f vert(appdata_img v) {
   
				v2f o;
				
				o.pos = UnityObjectToClipPos(v.vertex);
				
				o.uv = v.texcoord;
						 
				return o;
			}
		
			fixed4 frag(v2f i) : SV_Target {
   
				fixed4 renderTex = tex2D(_MainTex, i.uv);  
				  
				// Apply brightness
				fixed3 finalColor = renderTex.rgb * _Brightness;
				
				// Apply saturation
				//计算该像素对应的亮度值，创建一个饱和度为0的颜色值
				fixed luminance = 0.2125 * renderTex.r + 0.7154 * renderTex.g + 0.0721 * renderTex.b;
				fixed3 luminanceColor = fixed3(luminance, luminance, luminance);
				//_Saturation插值，得到饱和度
				finalColor = lerp(luminanceColor, finalColor, _Saturation);
				
				// Apply contrast
				//创建对比度为0的颜色值
				fixed3 avgColor = fixed3(0.5, 0.5, 0.5);
				finalColor = lerp(avgColor, finalColor, _Contrast);
				
				return fixed4(finalColor, renderTex.a);  
			}  
			  
			ENDCG
		}  
	}
	
	Fallback Off
}

边缘检测实现描边

边缘检测要用卷积核来做，计算梯度值

脚本

using UnityEngine;
using System.Collections;

public class