Shader "Custom/CameraRotate"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Rotation ("Rotation", Float) = 0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        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 _Rotation;

            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;
                
                // 顺时针旋转90度
                float angle = -1.57079633; // -90度转弧度
                float s = sin(angle);
                float c = cos(angle);
                
                // 将UV中心移到(0.5, 0.5)
                uv -= 0.5;
                
                // 旋转
                float2 rotatedUV;
                rotatedUV.x = uv.x * c - uv.y * s;
                rotatedUV.y = uv.x * s + uv.y * c;
                
                // 移回中心
                rotatedUV += 0.5;
                
                // 从中心截取横向区域
                // 旋转后的画面是竖向的，需要截取中间横向部分
                float aspectRatio = 0.6; // 预览框宽高比 / 旋转后相机宽高比
                float2 scale = float2(1.0, aspectRatio);
                float2 offset = float2(0.0, (1.0 - aspectRatio) * 0.5);
                
                rotatedUV = rotatedUV * scale + offset;
                
                // 裁剪越界
                if (rotatedUV.x < 0 || rotatedUV.x > 1 || rotatedUV.y < 0 || rotatedUV.y > 1)
                    return fixed4(0, 0, 0, 1);
                
                fixed4 col = tex2D(_MainTex, rotatedUV);
                return col;
            }
            ENDCG
        }
    }
}