新增回声扩散特效

unity/Assets/Light/shaders/EchoRing.shader

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+Shader "IndianOcean/EchoRing"
+{
+    // 回声红圈 Shader —— 配合 EchoSystem 使用
+    // 在地面（XZ平面）上绘制一个红色渐变圆环，圆环位置跟随全局 _EchoRadius
+    // 边缘使用 smoothstep 渐变，从圆环中心满透明度向两侧柔和消散
+    Properties
+    {
+        _RingColor  ("Ring Color", Color) = (1, 0.15, 0.1, 1)
+        _RingWidth  ("Ring Width (world units)", Float) = 2.5
+    }
+    SubShader
+    {
+        Tags
+        {
+            "RenderType"     = "Transparent"
+            "Queue"          = "Transparent+250"
+            "RenderPipeline" = "UniversalPipeline"
+        }
+        Blend SrcAlpha OneMinusSrcAlpha
+        ZWrite Off
+        ZTest Always
+        Cull Off
+
+        Pass
+        {
+            Name "EchoRing"
+            HLSLPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #pragma multi_compile_instancing
+
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+            struct Attributes
+            {
+                float4 positionOS : POSITION;
+                UNITY_VERTEX_INPUT_INSTANCE_ID
+            };
+
+            struct Varyings
+            {
+                float4 positionCS : SV_POSITION;
+                float3 worldPos   : TEXCOORD0;
+                UNITY_VERTEX_INPUT_INSTANCE_ID
+            };
+
+            CBUFFER_START(UnityPerMaterial)
+                float4 _RingColor;
+                float  _RingWidth;
+            CBUFFER_END
+
+            // 全局回声参数（由 EchoSystem 通过 Shader.SetGlobalX 设置）
+            float4 _EchoCenter;            // xy = 回声中心世界坐标 XZ
+            float  _EchoRingRadius;         // 红圈独立扩散半径
+            float  _EchoRingAlpha;         // 红圈独立透明度（独立于描边强度）
+
+            Varyings vert(Attributes input)
+            {
+                Varyings output;
+                UNITY_SETUP_INSTANCE_ID(input);
+                UNITY_TRANSFER_INSTANCE_ID(input, output);
+
+                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
+                output.worldPos   = TransformObjectToWorld(input.positionOS.xyz);
+                return output;
+            }
+
+            half4 frag(Varyings input) : SV_Target
+            {
+                // 世界空间 XZ 平面上的距离
+                float2 wp   = input.worldPos.xz;
+                float  dist = distance(wp, _EchoCenter.xy);
+
+                // 距离圆环中心的偏差
+                float distFromRing = abs(dist - _EchoRingRadius);
+
+                // 渐变：圆环中心满强度，两侧柔和消散
+                float halfW  = max(0.001, _RingWidth * 0.5);
+                float alpha  = 1.0 - smoothstep(0.0, halfW, distFromRing);
+
+                // 乘以红圈独立透明度（独立于描边消散时序）
+                alpha *= _EchoRingAlpha;
+
+                if (alpha < 0.001) discard;
+
+                return half4(_RingColor.rgb, alpha * _RingColor.a);
+            }
+            ENDHLSL
+        }
+    }
+    FallBack Off
+}

unity/Assets/Light/shaders/EchoRing.shader.meta

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+fileFormatVersion: 2
+guid: CX1JsiL7AnkPMkp0FGGR15PogOhTjb8ArRIm08D4oVWvMTimFo71lmA=
+ShaderImporter:
+  externalObjects: {}
+  defaultTextures: []
+  nonModifiableTextures: []
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: