Preface

Screen coordinates of Shader in Unity

1. Screen coordinates

1. Coordinates of screen pixels

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2. Screen coordinate normalization

Use the formula: Screen normalized coordinates = current pixels/total pixels

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2. Get the current screen pixels and total pixels in Unity

1. Get the total pixels of the screen, use the _ScreenParams parameter

_ScreenParams
Screen related parameters, unit is pixels.
x represents the width of the screen
y represents the height of the screen
z represents 1+1/screen width
w represents 1+1/screen height

2. Get the pixels on the current fragment

UNITY_VPOS_TYPE screenPos: VPOS
1. The position of the current fragment on the screen (unit is pixel, can be divided by _ScreenParams.xy for normalization), this function only supports #pragma target 3.0 and above compilation instructions 2. Under most
platforms VPOS returns a four-dimensional vector, and some platforms are two-dimensional vectors, so UNITY_VPOS_TYPE needs to be used to distinguish them uniformly. 3.
When using VPOS, you cannot define SV_POSITION in v2f, which will conflict, so you need to change the input of the vertex shader placed in the parameters of (), and SV_POSITION is added out.

How to use: Used when passing in parameters to the fragment shader

fixed4 frag (v2f i,UNITY_VPOS_TYPE screenPos : VPOS) : SV_Target
{
}

Because the type of VPOS is not uniform on different platforms, some are float2 and some are float4, so we use the type UNITY_VPOS_TYPE provided by Unity and let Unity handle it automatically.

When using UNITY_VPOS_TYPE screenPos: VPOS as the input of the fragment shader, the input of the vertex shader needs to be modified.

Modified code:

Shader "MyShader/P0_10_3"
{
    SubShader
    {
        
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct v2f
            {
                float2 uv : TEXCOORD0;
            };
            //在顶点着色器的输入处，不用appdata,直接使用用到的参数，防止 SV_POSITION 重复定义
            v2f vert (
                float4 vertex : POSITION,
                out float4 pos : SV_POSITION
            )
            {
                v2f o;
                pos = UnityObjectToClipPos(vertex);
                return o;
            }

            fixed4 frag (v2f i,UNITY_VPOS_TYPE screenPos : VPOS) : SV_Target
            {
                
                float2 screenUV = screenPos.xy / _ScreenParams.xy;
                return fixed4(screenUV,0,0);
            }
            ENDCG
        }
    }
}

Effect:
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Output the effect of screen normalized x: return screenUV.x;

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Output the effect of screen normalization y: return screenUV.y;