UnityShader屏幕后处理

屏幕后处理实际为利用shader处理最终呈现在相机中的图片。但是shader不能直接与c#数据传递，所以创建material来沟通。

1 创建shader

shader中的_MainTex为默认相机最终图片所以必须。然后就可以调整整张图片的风格渲染。

2 检查这个平台是不是支持图片效果。

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

return true;
}

3 检查一步骤中的shader是不是被各个平台支持，并且创建材质

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;
}
}

4 在c#脚本中处理图片

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);
}
}

OnRenderImage函数会在所有不透明和透明的Pass执行完毕后被调用(可选)。参数src对应源纹理，dest为目标渲染纹理。通过material处理shader中的src纹理变为dest纹理。处理过程为material.SetFloat(“_Contrast”, contrast);等等。新纹理赋予旧纹理为Graphics.Blit(src, dest, material);处理的纹理为shader中的_MatinTex。

5源码

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;
}
}
}

BrightnessSaturationAndContrast.cs

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;

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);
}
}
}

Brightness.shader

Shader "Custom/Brightness Saturation And Contrast" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_Brightness ("Brightness", Float) = 1
_Saturation("Saturation", Float) = 1
_Contrast("Contrast", Float) = 1
}
SubShader {
Pass {
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
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
}