Shader "Custom/URPOutline"
{
    Properties
    {
        _BaseColor("Base Color", Color) = (1,1,1,1)
        _OutlineColor("Outline Color", Color) = (1,0,0,1)
        _OutlineWidth("Outline Width", Range(0, 0.1)) = 0.05
    }
    
    SubShader
    {
        Tags 
        { 
            "RenderType"="Opaque"
            "RenderPipeline"="UniversalPipeline"
            "Queue"="Geometry"
        }
        
        // 第一个Pass：渲染描边
        Pass
        {
            Name "Outline"
            Tags { "LightMode" = "SRPDefaultUnlit" }
            
            Cull Front
            ZWrite On
            
            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 positionCS : SV_POSITION;
            };
            
            CBUFFER_START(UnityPerMaterial)
                float4 _OutlineColor;
                float _OutlineWidth;
            CBUFFER_END
            
            Varyings vert(Attributes input)
            {
                Varyings output;
                
                // 沿法线方向膨胀顶点
                float3 normalOS = normalize(input.normalOS);
                float3 positionOS = input.positionOS.xyz + normalOS * _OutlineWidth;
                
                output.positionCS = TransformObjectToHClip(positionOS);
                return output;
            }
            
            half4 frag(Varyings input) : SV_Target
            {
                return _OutlineColor;
            }
            ENDHLSL
        }
        
        // 第二个Pass：渲染物体本身
        Pass
        {
            Name "ForwardLit"
            Tags { "LightMode" = "UniversalForward" }
            
            Cull Back
            ZWrite On
            
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS
            
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
            
            struct Attributes
            {
                float4 positionOS : POSITION;
                float3 normalOS : NORMAL;
            };
            
            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 normalWS : TEXCOORD0;
            };
            
            CBUFFER_START(UnityPerMaterial)
                float4 _BaseColor;
            CBUFFER_END
            
            Varyings vert(Attributes input)
            {
                Varyings output;
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.normalWS = TransformObjectToWorldNormal(input.normalOS);
                return output;
            }
            
            half4 frag(Varyings input) : SV_Target
            {
                // 基础光照
                Light mainLight = GetMainLight();
                float3 normalWS = normalize(input.normalWS);
                float NdotL = saturate(dot(normalWS, mainLight.direction));
                float3 color = _BaseColor.rgb * (mainLight.color * NdotL + 0.2);
                
                return half4(color, _BaseColor.a);
            }
            ENDHLSL
        }
    }
}