Shader "Custom/TrigonometricRotation"
{
    Properties
    {
        _RotateSpeed("旋转幅度",Range(1,4)) = 1
        _MainTex("贴图",2D) = "White"{}
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue" = "Geometry" "IgnoreProjector" = "True" "DisableBatching" = "True" }

        pass
        {
            CGPROGRAM
            //相当于 引入编辑顶点方法的 程序集
            #pragma vertex vert 
            //相当于 引入编辑片元的程序集
            #pragma fragment frag
            
            //引入Unity自建的函数库
            #include "UnityCG.cginc"
            
            struct appdata
            {
                float4 pos : POSITION;
                float2 uv : TEXCOORD0;
            };
            
            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv : TEXCOORD0;
            };
            
            float _RotateSpeed;
            sampler2D _MainTex;
            float4 _MainTex_ST;            

            v2f vert(in appdata data)
            {
                float angle = length(data.pos) * _SinTime.w / _RotateSpeed;
             
                v2f v;
                //所谓得观察空间就是 剪裁空间
                //视图矩阵 * 投影矩阵 * 模型矩阵 +=》 模型到 视图投影得转换 // 相机视图
                float4x4 m =
                {
                    float4(cos(angle),0,sin(angle),0),
                    float4(0,1,0,0),
                    float4(-sin(angle),0,cos(angle),0),
                    float4(0,0,0,1)
                };
                float4 p = mul(m,data.pos);
                v.pos = UnityObjectToClipPos(p);
                v.uv = TRANSFORM_TEX(data.uv,_MainTex);
                return v;
            }
            
            fixed4 frag(v2f IN) : SV_TARGET
            {
                return tex2D(_MainTex,IN.uv);
            }
            ENDCG
        }  
    }
}