Shader "SLS/Postprocessing/RadialBlur"
{
    SubShader
    {
        Tags
        {
            "RenderType" = "Opaque"
            "RenderPipeline" = "UniversalPipeline"
        }
        ZWrite Off
        Cull Off
        
        HLSLINCLUDE
        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
        #include "Packages/com.unity.render-pipelines.core/Runtime/Utilities/Blit.hlsl"

        // 变量定义
        float4 _RadialBlurParams;
        #define _BlurRadius _RadialBlurParams.x
        #define _RadialCenter _RadialBlurParams.yz

        // --- 具体实现函数 ---

        half4 RadialBlurPassFragment_4Tap(Varyings input): SV_Target
        {
            float2 uv = input.texcoord - _RadialCenter;
            half scale = 1;
            half4 color = SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
            
            scale = _BlurRadius + 1;
            color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
            scale = 2 * _BlurRadius + 1;
            color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
            scale = 3 * _BlurRadius + 1;
            color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);

            color *= 0.25f; // 1/4
            return color;
        }

        half4 RadialBlurPassFragment_8Tap(Varyings input): SV_Target
        {
            float2 uv = input.texcoord - _RadialCenter;
            half4 color = 0;
            // 为了代码简洁，这里可以使用循环，但在 Shader 中手动展开(Unroll)通常性能更好或便于控制
            // 这里保留你原本的展开逻辑
            [unroll]
            for(int i=0; i<8; i++)
            {
                half scale = i * _BlurRadius + 1;
                color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
            }
            return color * 0.125f;
        }
        

        half4 RadialBlurPassFragment_12Tap(Varyings input): SV_Target
        {
             float2 uv = input.texcoord - _RadialCenter;
             half4 color = 0;
             for(int i=0; i<12; i++) {
                half scale = i * _BlurRadius + 1;
                color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
             }
             return color * 0.0833f;
        }
        
        half4 RadialBlurPassFragment_16Tap(Varyings input): SV_Target
        {
             float2 uv = input.texcoord - _RadialCenter;
             half4 color = 0;
             for(int i=0; i<16; i++) {
                half scale = i * _BlurRadius + 1;
                color += SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_LinearClamp, uv * scale + _RadialCenter);
             }
             return color * 0.0625f;
        }
        
        ENDHLSL

        Pass
        {
            Name "Radial Blur 4 Tap"
            HLSLPROGRAM
            #pragma vertex Vert
            #pragma fragment RadialBlurPassFragment_4Tap
            ENDHLSL
        }

        Pass
        {
            Name "Radial Blur 8 Tap"
            HLSLPROGRAM
            #pragma vertex Vert
            #pragma fragment RadialBlurPassFragment_8Tap
            ENDHLSL
        }
        
        Pass
        {
            Name "Radial Blur 12 Tap"
            HLSLPROGRAM
            #pragma vertex Vert
            #pragma fragment RadialBlurPassFragment_12Tap
            ENDHLSL
        }

        Pass
        {
            Name "Radial Blur 16 Tap"
            HLSLPROGRAM
            #pragma vertex Vert
            #pragma fragment RadialBlurPassFragment_16Tap
            ENDHLSL
        }
    }
}