0x00 序言
本文是《Unity Shader入門精要》讀書筆記,最近接觸到項目中用到了模糊處理,經過查閱資料,發覺模糊處理是屏幕後處理技術中的一種,就從屏幕後處理技術開始學習。[使用的Unity版本:5.6.1f1]0x01效果圖
0x02 屏幕後處理的定義
屏幕後處理,通常指的是在渲染完整個場景得到屏幕圖像後,再對這個圖像一系列操作,實現各種屏幕特效。
想要實現屏幕後處理的基礎在於得到渲染後的屏幕圖像,即抓取屏幕,而Unity爲我們提供了這樣一個方便的接口——OnRenderImage函數:
MonoBehaviour.OnRenderImage(RenderTexture src, RenderTexture dest)
0x03 後處理過程
1.需要在攝像機中添加一個用於屏幕後處理的腳本。在這個腳本中,我們會實現OnRenderImage函數來獲取當前屏幕的渲染紋理;
2.調用Graphics.Blit函數使用特定的Unity Shader來對當前圖像進行處理;
3.把返回的渲染紋理顯示到屏幕上。0x04 後處理腳本代碼
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
[ExecuteInEditMode] //編輯器狀態下可以直接看到運行結果
[RequireComponent (typeof(Camera))]
public class BrightnessSaturationAndContrast : MonoBehaviour {
protected void CheckResources()
{
bool isSupported = CheckSupport();
if (isSupported == false)
{
NotSupported();
}
}
protected bool CheckSupport()
{
if (SystemInfo.supportsImageEffects == false)
{
Debug.LogWarning("This platform does not support image effects or render textures.");
return false;
}
return true;
}
protected void NotSupported()
{
enabled = false;
}
void Start () {
CheckResources();
}
//第一個參數指定了特效需要使用的Shader,第二個參數則是用於後期處理的材質。
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;
}
}
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;
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);
}
}
}
- 0x05 Shader代碼
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Brightness Saturation And Contrast"{
//聲明本例使用的各個屬性
Properties{
_MainTex("Base (RGB)", 2D) = "white" {}
_Brightness("Brightness", Float) = 1
_Saturation("Saturation", Float) = 1
_Contrast("Contrast", Float) = 1
}
//定義用於屏幕後處理的pass
SubShader{
Pass{
//關閉深度寫入
//爲了防止它“擋住”在其後面被渲染的物體。
ZTest Always Cull Off ZWrite Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
//在CG代碼塊中聲明對應的變量
sampler2D _MainTex;
half _Brightness;
half _Saturation;
half _Contrast;
//定義頂點着色器
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;
}
//定義片元着色器
fixed4 frag(v2f i) : SV_Target{
fixed4 renderTex = tex2D(_MainTex, i.uv);
//Apply brightness
fixed3 finalColor = renderTex.rgb * _Brightness;
//Apply saturation
//['luːmɪn(ə)ns]亮度
fixed luminance = 0.2125 * renderTex.r + 0.7154 * renderTex.g + 0.0721 * renderTex.b;
fixed3 luminanceColor = fixed3(luminance, luminance, luminance);
finalColor = lerp(luminanceColor, finalColor, _Saturation);
//Apply contrast
fixed3 avgColor = fixed3(0.5, 0.5, 0.5);
finalColor = lerp(avgColor, finalColor, _Contrast);
return fixed4(finalColor, renderTex.a);
}
ENDCG
}
}
Fallback Off
}