Shader "URP/WhiteOutline"
{
    Properties
    {
        _OutlineWidth("Outline Width", Range(0, 0.1)) = 0.00003
        _OutlineColor("Outline Color", Color) = (0, 0, 0, 1)
        _Color("Base Color", Color) = (1, 1, 1, 1)
    }

    SubShader
    {
        Tags 
        { 
            "RenderType" = "Opaque"
            "RenderPipeline" = "UniversalPipeline"
        }

        // 描边Pass
        Pass
        {
            Name "Outline"
            Tags { "LightMode" = "SRPDefaultUnlit" }
            
            Cull Front
            
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS : POSITION;
                float3 normalOS : NORMAL;
            };

            struct Varyings
            {
                float4 positionHCS : SV_POSITION;
            };

            CBUFFER_START(UnityPerMaterial)
                float _OutlineWidth;
                float4 _OutlineColor;
            CBUFFER_END

            Varyings vert(Attributes IN)
            {
                Varyings OUT;
                
                // 顶点扩展
                float3 normalOS = normalize(IN.normalOS);
                float3 positionOS = IN.positionOS.xyz + normalOS * _OutlineWidth;
                
                // 转换到裁剪空间
                OUT.positionHCS = TransformObjectToHClip(positionOS);
                return OUT;
            }

            half4 frag(Varyings IN) : SV_Target
            {
                return _OutlineColor;
            }
            ENDHLSL
        }

        // 主颜色Pass
        Pass
        {
            Name "ForwardLit"
            Tags { "LightMode" = "UniversalForward" }

            Cull Back

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS : POSITION;
            };

            struct Varyings
            {
                float4 positionHCS : SV_POSITION;
            };

            CBUFFER_START(UnityPerMaterial)
                float4 _Color;
            CBUFFER_END

            Varyings vert(Attributes IN)
            {
                Varyings OUT;
                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
                return OUT;
            }

            half4 frag(Varyings IN) : SV_Target
            {
                return _Color;
            }
            ENDHLSL
        }
    }
}