UV旋转shader

Shader "Custom/Simple"
{
    Properties
    {
        _Color("Base Color", Color) = (1,1,1,1)
        _MainTex("Base(RGB)", 2D) = "white" {}
        _RSpeed("RotateSpeed", Range(1, 100)) = 30
    }
    
    SubShader
    {
        tags{"Queue" = "Transparent" "RenderType" = "Transparent" "IgnoreProjector" = "True"}
        Blend SrcAlpha OneMinusSrcAlpha
        
        Pass
        {
            Name "Simple"
            Cull off
            
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            
            float4 _Color;
            sampler2D _MainTex;
            float _RSpeed;
            
            struct v2f
            {
                float4 pos:POSITION;
                float4 uv:TEXCOORD0;
            };
            
            v2f vert(appdata_base v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.uv = v.texcoord;
                return o;
            }
            
            half4 frag(v2f i):COLOR
            {
                float2 uv = i.uv.xy - float2(0.5, 0.5);//将旋转点从左上角唯一到中心点（UV默认中（0,0）点为左上角）
                uv = float2(uv.x * cos(_RSpeed * _Time.w) - uv.y * sin(_RSpeed * _Time.w), 
                            uv.x * sin(_RSpeed * _Time.w) + uv.y * cos(_RSpeed * _Time.w));//计算旋转，矩阵乘法
                
                uv += float2(0.5, 0.5);
                
                half4 c = tex2D(_MainTex , uv) * _Color;//以UV为坐标取得纹理_MainTex对应位置的像素内容。
                return c;
            }
            
            ENDCG
        }
    }
}