Shader "Custom/TransparentOutline"
{
    Properties
    {
        _MainColor ("Main Color", Color) = (1,1,1,0.5)
        _OutlineColor ("Outline Color", Color) = (0,0,0,1)
        _OutlineWidth ("Outline Width", Range(0.001, 0.1)) = 0.02
    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue"="Transparent" }
        LOD 100

        // First Pass: Render the Outline Behind the Mesh
        Pass {
            Name "Outline"
            Cull Front
            ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

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

            struct v2f {
                float4 positionCS : SV_POSITION;
            };

            float _OutlineWidth;
            float4 _OutlineColor;

            v2f vert(appdata_t v) {
                v2f o;
                float3 normalWS = TransformObjectToWorldNormal(v.normalOS);
                float3 positionWS = TransformObjectToWorld(v.positionOS.xyz);
                positionWS += normalWS * _OutlineWidth;
                o.positionCS = TransformWorldToHClip(positionWS);
                return o;
            }

            half4 frag(v2f i) : SV_Target {
                return _OutlineColor;
            }
            ENDHLSL
        }

        // Second Pass: Render the Transparent Mesh on Top
        Pass {
            Name "Main"
            Cull Back
            ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct appdata_t {
                float4 positionOS : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f {
                float4 positionCS : SV_POSITION;
                float2 uv : TEXCOORD0;
            };

            float4 _MainColor;

            v2f vert(appdata_t v) {
                v2f o;
                o.positionCS = TransformObjectToHClip(v.positionOS);
                o.uv = v.uv;
                return o;
            }

            half4 frag(v2f i) : SV_Target {
                return _MainColor;
            }
            ENDHLSL
        }
    }
}