Unity shader learning (I) understanding the basic structure of unity shader

I'm going to learn it seriously recently Unity Of Shader, It will be used in future projects , Although it is said to use other people's shader Very comfortable , But no matter how easy it is to use, it is also someone else's , I can't understand , So you have to understand it yourself . Let's get to know each other today shader Structure , And I am right. unity shader Simple understanding of rendering .

1. Simple understanding of the computer rendering process

First of all, learn shader, You must understand the rendering process of the computer , Here I recommend you to Baidu yourself , The following references ：
Unity Technical art
Computer rendering process
Simple understanding of the computer rendering process
Conceptually, we generally divide the rendering process of a computer into several stages ：
1. Application stage ： Mainly from CPU Process light 、 Data such as models , Entity data forming point, line and plane .
2. Geometric stage ： Processing point, line and plane information .
3. Grating stage ： Add texture 、 Color, etc. .
（ Be careful ： The above stage is to simplify the process , The actual operation is more complicated ）

2. know Unity Shader Structure

open Unity, Create a shader , You can see that the default shader is standard pbr shader Rendering mode

So let's create another one shader, Right click the mouse 》Shader》 Choose any one , Here we choose the one without light Unlit Shader, Create the following ：

Double-click to open shader, What I'm using here is VScode To write Shader,Unity Of Shader It uses shaderlab Language , Encapsulate the underlying interface , Just call it directly , Compatible with all platforms .

Shader "Unlit/shader1"
{
    
    Properties
    {
    
        _MainTex ("Texture", 2D) = "white" {
    }
    }
    SubShader
    {
    
        Tags {
     "RenderType"="Opaque" }
        LOD 100

        Pass
        {
    
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

            struct v2f
            {
    
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

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

            fixed4 frag (v2f i) : SV_Target
            {
    
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDCG
        }
    }
}

The top one is Shader Naming operations for , Don't care

Shader "Unlit/shader1"

And then there was Properties block , Here are the predefined parameter variables , Can pass Unity Panel adjustment

  Properties
    {
    
        _MainTex ("Texture", 2D) = "white" {
    }
    }

The main form of definition is
_Name (“Display Name”,Type) = Default Value
Type Types include ：
Color Color
Int Integers
Float Floating point numbers
Vector Four dimensional number
2D texture
3D texture
Cube Cubic texture

SubShader List of similar renderings , You can provide a variety of image quality options for rendering
Tags: Set up special rendering methods , For example, for transparent objects 、 Rendering of translucent objects
LOD: Set the detail control of rendering , Processing refers to the processing of equipment performance , You can leave it at that

  SubShader
    {
    
        Tags {
     "RenderType"="Opaque" }
        LOD 100

Pass block , All the rendering is done here , from CGPROGRAM Start ,ENDCG end
Generally speaking , There can be multiple Pass

      Pass
        {
    
        CGPROGRAM
        ENDCG

		}

#pragma vertex/fragment name They are the naming of vertex shader and slice shader respectively
Vertex shaders and slice shaders are defined , We need to deal with this ,
See the comments in the code for details

     CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // introduce UnityCG
            #include "UnityCG.cginc"
			
            struct appdata
            {
    
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
    
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
			// Vertex shader processing in the geometric phase , You need to input the data of an application stage appdata, That is, point, line, surface and other information 
			// Process after input , Returns the data used by a slice shader v2f
            v2f vert (appdata v)
            {
    
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }
			// Grating stage , Enter a structure that needs rasterization v2f, Return color information 
            fixed4 frag (v2f i) : SV_Target
            {
    
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDCG

The above stage , In summary ：
vert Processed the information of points
frag Process the point information and output the color
I don't want to know the details , In the next section, let's write our own code