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unity/Assets/Light/shaders/DarknessOverlay.shader

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+Shader "IndianOcean/DarknessOverlay"
+{
+    // 黑暗遮罩 Shader v2 —— 乘法混合版（纯黑暗 + 光源，不含回声）
+    // 回声描边已独立到 SpriteEchoOutline shader，由 EchoSystem 全局参数驱动。
+    //
+    // 乘法混合：finalColor = srcColor * dstColor
+    // 黑暗区域：sceneColor * 0 = 纯黑（精灵完全看不见）
+    // 光照区域：sceneColor * 1 = 原色（完全可见）
+    Properties
+    {
+        _DarknessColor ("黑暗底色（夜间微光色调）", Color) = (0.01, 0.01, 0.02, 1)
+        _MinBrightness ("最小亮度（0=纯黑不可见, 0.05=微光）", Range(0, 0.3)) = 0.0
+        _LightSoftness ("光线柔和度（边缘渐变宽度）", Range(0.01, 1.0)) = 0.35
+    }
+    SubShader
+    {
+        Tags
+        {
+            "RenderType" = "Transparent"
+            "Queue" = "Transparent+100"
+            "RenderPipeline" = "UniversalPipeline"
+        }
+        Blend DstColor Zero
+        ZWrite Off
+        ZTest Always
+        Cull Off
+
+        Pass
+        {
+            Name "DarknessOverlay"
+            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;
+                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 _DarknessColor;
+                float  _MinBrightness;
+                float  _LightSoftness;
+            CBUFFER_END
+
+            // 光源数据数组：xy = 世界坐标 XZ, z = 半径, w = 强度(0~1)
+            float4 _LightData[64];
+            int    _LightCount;
+
+            Varyings vert(Attributes input)
+            {
+                Varyings output;
+                UNITY_SETUP_INSTANCE_ID(input);
+                UNITY_TRANSFER_INSTANCE_ID(input, output);
+
+                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
+                output.uv = input.uv;
+                output.worldPos = TransformObjectToWorld(input.positionOS.xyz);
+                return output;
+            }
+
+            half4 frag(Varyings input) : SV_Target
+            {
+                // 2.5D 俯视角：用世界坐标的 XZ 平面计算距离
+                float2 worldPos = input.worldPos.xz;
+                float lightAmount = 0.0;
+
+                // 常规光源
+                for (int i = 0; i < _LightCount; i++)
+                {
+                    float2 lightPos = _LightData[i].xy;
+                    float  radius   = _LightData[i].z;
+                    float  intensity= _LightData[i].w;
+
+                    float dist = distance(worldPos, lightPos);
+                    float innerRadius = radius * (1.0 - _LightSoftness);
+                    float light = 1.0 - smoothstep(innerRadius, radius, dist);
+                    light *= intensity;
+                    lightAmount = max(lightAmount, light);
+                }
+
+                // 最小亮度：全黑区域是否允许微微看到东西
+                lightAmount = max(lightAmount, _MinBrightness);
+
+                // 从黑暗底色插值到白色
+                float3 maskColor = lerp(_DarknessColor.rgb, float3(1.0, 1.0, 1.0), lightAmount);
+                return half4(maskColor, 1.0);
+            }
+            ENDHLSL
+        }
+    }
+    FallBack Off
+}