[unity rendering] customized screen post-processing

Custom screen post-processing is not difficult , The steps are divided into two parts ,1. Set shaders and... For picture processing Shader;2. stay C# The code uses OnrenderImage Function to process the camera picture .

1. establish Shader And shaders

Use ImageEffect（ Image effects ） Type of Shader.
Shader It should be named _MainTex Main texture of , For reception C# Method to pass in the screen image . Otherwise, it is impossible to perform post-processing .
What will be written shader Assign to the shader .
Here is a simple blur shader.

Shader "Hidden/Image_Fuzzy"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Offset("Offset", Range(0, 0.05)) = 0.02

    }
    SubShader
    {
        // No culling or depth
        //Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;
            float _Offset;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                // just invert the colors
                //col.rgb = 1 - col.rgb;
            fixed4 c1 = tex2D(_MainTex, i.uv - (_Offset, 0));
            fixed4 c2 = tex2D(_MainTex, i.uv + (_Offset, 0));
            fixed4 c3 = tex2D(_MainTex, i.uv + (0, _Offset));
            fixed4 c4 = tex2D(_MainTex, i.uv - (0, _Offset));
            return( col + c1 + c2 + c3 + c4) / 5;;
            }
            ENDCG
        }
    }
}

2. call C# in OnRenderImage Method

OnRenderImage Post processing effect . Called after all the rendering operations of the image have been completed .
This function allows you to process the final image using shader based filters , To modify the final image . source Render textures for incoming images .destination Texture the output result .
When the camera is attached with multiple image filters , They process the images in sequence according to the following methods ： Pass the target of the first filter as the source to the next filter , And so on .

 Material material;

    void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
    
        // Copy the source Render Texture to the destination,
        // applying the material along the way.
        Graphics.Blit(source, destination, material);
    }

Graphics.Blit (Texture source, RenderTexture dest, Material mat, int pass= -1) function

Use shaders to copy the source texture to the target render texture .
source For the input image , Corresponding shader Medium _MainTex attribute , Fill in OnRenderImage Medium source that will do .
dest For the output image , Fill in OnRenderImage Medium destination that will do .
mat Materials used for post-treatment .

function Unity You can see the post-processing effect .

Be careful ：1. with OnRenderImage Method , Need to hang to Camera Only on components can .
2.Shader It should be named _MainTex Main texture of , For reception C# Method to pass in the screen image . Otherwise, it is impossible to perform post-processing .