Shader "Unlit/Rotate"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _RotateSpeed("RotateSpeed",Float) = 1
    }
    SubShader
    {
        Tags {"Queue" = "Transparent" "RenderType"="Transparent" }
        Blend SrcAlpha OneMinusSrcAlpha

        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;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _RotateSpeed;

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

            fixed4 frag (v2f i) : SV_Target
            {

                float2 uv = i.uv.xy - float2(0.5, 0.5);  
                //旋转矩阵公式  
                uv = float2(uv.x * cos(_RotateSpeed * _Time.y) - uv.y * sin(_RotateSpeed * _Time.y),  
                            uv.x * sin(_RotateSpeed * _Time.y) + uv.y * cos(_RotateSpeed * _Time.y));  
                //恢复纹理位置  
                uv += float2(0.5, 0.5); 
                fixed4 col = tex2D(_MainTex, uv);
                return col;
            }
            ENDCG
        }
    }
}