优化回声描边逻辑

unity/Assets/Light/shaders/SpriteWithGroundClip.shader

@@ -1,7 +1,8 @@
 Shader "Custom/SpriteWithGroundClip"
 {
-    // 带地面裁剪的Sprite Shader
+    // 带地面裁剪和阴影的Sprite Shader
     // 当Sprite的世界Y坐标低于地面高度时，会被裁剪掉
+    // 支持投射阴影（可选）
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
@@ -9,6 +10,12 @@ Shader "Custom/SpriteWithGroundClip"
         [MaterialToggle] _EnableClip ("启用裁剪", Float) = 1.0
         _ClipSoftness ("裁剪边缘柔和度", Range(0, 0.5)) = 0.05
         
+        // 阴影设置
+        [MaterialToggle] _CastShadow ("投射阴影", Float) = 1.0
+        _ShadowOpacity ("阴影透明度", Range(0, 1)) = 0.5
+        _ShadowOffset ("阴影偏移 (Y方向)", Float) = -0.1
+        _ShadowColor ("阴影颜色", Color) = (0, 0, 0, 0.5)
+        
         // 颜色
         _Color ("颜色", Color) = (1, 1, 1, 1)
     }
@@ -110,6 +117,122 @@ Shader "Custom/SpriteWithGroundClip"
             }
             ENDHLSL
         }
+        
+        // 阴影Pass
+        Pass
+        {
+            Name "ShadowCaster"
+            Tags { "LightMode" = "ShadowCaster" }
+            
+            ZWrite On
+            ZTest LEqual
+            Cull Off
+            
+            HLSLPROGRAM
+            #pragma vertex ShadowPassVertex
+            #pragma fragment ShadowPassFragment
+            #pragma multi_compile_instancing
+
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Shadows.hlsl"
+            struct Attributes
+            {
+                float4 positionOS : POSITION;
+                float3 normalOS : NORMAL;
+                float2 uv : TEXCOORD0;
+                UNITY_VERTEX_INPUT_INSTANCE_ID
+            };
+
+            struct Varyings
+            {
+                float4 positionCS : SV_POSITION;
+                float2 uv : TEXCOORD0;
+                float3 worldPos : TEXCOORD1;
+                UNITY_VERTEX_INPUT_INSTANCE_ID
+            };
+
+            CBUFFER_START(UnityPerMaterial)
+                float4 _MainTex_ST;
+                float4 _Color;
+                float _GroundHeight;
+                float _EnableClip;
+                float _ClipSoftness;
+                float _CastShadow;
+                float _ShadowOpacity;
+                float _ShadowOffset;
+                float4 _ShadowColor;
+            CBUFFER_END
+
+            TEXTURE2D(_MainTex);
+            SAMPLER(sampler_MainTex);
+
+            Varyings ShadowPassVertex(Attributes input)
+            {
+                Varyings output;
+                UNITY_SETUP_INSTANCE_ID(input);
+                UNITY_TRANSFER_INSTANCE_ID(input, output);
+
+                // URP阴影Pass需要使用特殊的矩阵变换
+                float3 positionWS = TransformObjectToWorld(input.positionOS.xyz);
+                float4 positionCS = TransformWorldToHClip(positionWS);
+                
+                // 应用阴影偏移（向光源方向偏移）
+                #if UNITY_REVERSED_Z
+                    positionCS.z -= unity_LightData.z;
+                #else
+                    positionCS.z += unity_LightData.z;
+                #endif
+                
+                output.positionCS = positionCS;
+                output.uv = TRANSFORM_TEX(input.uv, _MainTex);
+                output.worldPos = positionWS;
+                return output;
+            }
+
+            half4 ShadowPassFragment(Varyings input) : SV_Target
+            {
+                UNITY_SETUP_INSTANCE_ID(input);
+
+                // 如果不投射阴影，直接丢弃
+                if (_CastShadow < 0.5)
+                {
+                    discard;
+                }
+
+                // 采样纹理获取Alpha
+                half4 texColor = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv);
+                half alpha = texColor.a * _Color.a;
+
+                // 地面裁剪逻辑（与主Pass相同）
+                if (_EnableClip > 0.5)
+                {
+                    float worldY = input.worldPos.y;
+                    float distanceToGround = worldY - _GroundHeight;
+                    
+                    if (distanceToGround < 0)
+                    {
+                        float clipAlpha = smoothstep(0, _ClipSoftness, distanceToGround);
+                        alpha *= clipAlpha;
+                        
+                        if (alpha < 0.01)
+                        {
+                            discard;
+                        }
+                    }
+                }
+
+                // 如果Alpha太低，不投射阴影
+                if (alpha < 0.1)
+                {
+                    discard;
+                }
+
+                // 输出阴影（URP阴影格式）
+                return half4(0, 0, 0, alpha * _ShadowOpacity);
+            }
+            ENDHLSL
+        }
     }
     FallBack "Sprites/Default"
 }