DTM Trail

Assets/Shaders/Grid.shader

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+Shader "Custom/Grid"
+{
+    Properties
+    {
+        _LineColor("Line Color", Color) = (1,1,1,1)
+        _BackgroundColor("Background Color", Color) = (0,0,0,0)
+        _GridScale("Grid Scale", Float) = 1
+        _LineWidth("Line Width", Float) = 0.05
+        _Fade("Fade", Float) = 0.1
+        _Plane("Plane (0: XZ, 1: XY, 2: YZ)", Float) = 0
+        _DisappearStartDistance("Disappear Start Distance", Float) = 50
+        _DisappearEndDistance("Disappear End Distance", Float) = 100
+    }
+    SubShader
+    {
+        Tags { "RenderType"="Transparent" "Queue"="Transparent" }
+        LOD 100
+
+        Pass
+        {
+            Name "GridPass"
+            Cull Off
+            Blend SrcAlpha OneMinusSrcAlpha
+            ZWrite Off
+
+            HLSLPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+            // 内置变量：摄像机在世界空间中的位置
+            //float3 _WorldSpaceCameraPos;
+
+            struct Attributes
+            {
+                float4 vertex : POSITION;
+                float2 uv : TEXCOORD0;
+            };
+
+            struct Varyings
+            {
+                float4 position : SV_POSITION;
+                float3 worldPos : TEXCOORD0;
+            };
+
+            CBUFFER_START(UnityPerMaterial)
+            float4 _LineColor;
+            float4 _BackgroundColor;
+            float _GridScale;
+            float _LineWidth;
+            float _Fade;
+            float _Plane;
+            float _DisappearStartDistance;
+            float _DisappearEndDistance;
+            CBUFFER_END
+
+            Varyings vert(Attributes IN)
+            {
+                Varyings OUT;
+                OUT.position = TransformObjectToHClip(IN.vertex);
+                OUT.worldPos = TransformObjectToWorld(IN.vertex).xyz;
+                return OUT;
+            }
+
+            // 根据 _Plane 选择二维坐标
+            float2 GetGridCoordinates(float3 pos)
+            {
+                if (_Plane < 0.5)      // XZ 平面
+                    return pos.xz;
+                else if (_Plane < 1.5) // XY 平面
+                    return pos.xy;
+                else                   // YZ 平面
+                    return pos.yz;
+            }
+
+            // 根据 _Plane 获取摄像机在网格平面上的位置
+            float2 GetCameraPlanePosition()
+            {
+                if (_Plane < 0.5)      // XZ 平面：摄像机投影到 XZ
+                    return _WorldSpaceCameraPos.xz;
+                else if (_Plane < 1.5) // XY 平面：摄像机投影到 XY
+                    return _WorldSpaceCameraPos.xy;
+                else                   // YZ 平面：摄像机投影到 YZ
+                    return _WorldSpaceCameraPos.yz;
+            }
+
+            half4 frag(Varyings IN) : SV_Target
+            {
+                // 计算二维网格坐标并乘以 _GridScale
+                float2 gridCoord = GetGridCoordinates(IN.worldPos) * _GridScale;
+                // 用 frac 与 fwidth 实现平滑网格线（抗锯齿）
+                float2 grid = abs(frac(gridCoord - 0.5) - 0.5) / fwidth(gridCoord);
+                float lineIntensity = 1.0 - smoothstep(0.0, _LineWidth, min(grid.x, grid.y));
+                
+                // 计算摄像机在平面上的位置与当前片元的二维距离
+                float2 camPos2D = GetCameraPlanePosition();
+                float2 fragPos2D = GetGridCoordinates(IN.worldPos);
+                float dist = distance(fragPos2D, camPos2D);
+                
+                // 超过 100 米开始淡出，到 200 米完全透明
+                float distanceFade = saturate((_DisappearEndDistance - dist) / _DisappearStartDistance);
+                
+                // 最终 alpha 是网格线强度乘以距离淡出因子
+                float finalAlpha = lineIntensity * distanceFade;
+                
+                // 背景颜色始终透明，所以直接输出网格线颜色与 alpha
+                return float4(_LineColor.rgb, finalAlpha);
+            }
+            ENDHLSL
+        }
+    }
+    FallBack "Diffuse"
+}