ichni_Official/Assets/ThemeBundles/DepartureToMultiverse/Shaders/DTM_RandomGridTube.shader

Shader "Soullies/DTM_RandomGridTube"
{
    Properties
    {
        [HDR]_Color0("Color0", Color) = (1, 1, 1, 0)
        
        [Header(Pattern Settings)]
        _PatternSize("Pattern Size (X, Y)", Vector) = (2.0, 2.0, 0, 0)
        _GridDensity("Grid Density (Quantity Multiplier)", Float) = 1.0
        _BaseSpeed("Base Speed (Static)", Float) = 1.0
        _TimeAngle("Time Angle / Offset (Dynamic)", Float) = 0.0
        
        [Header(Edge Settings)]
        _StepA("Step A", Range(0, 1)) = 0.293
        _StepB("Step B", Range(0, 1)) = 0.345

        [Header(Seam Hiding)]
        _SeamRotation("Seam Angle Offset", Range(-180, 180)) = -90.0
        _SeamFadeWidth("Seam Cut Width", Range(0.0, 1.0)) = 0.2
        _SeamFadeSmoothness("Seam Softness", Range(0.0, 1.0)) = 1.0

        [Header(Tube Specific Settings)]
        _FadeFar("Fade Far (Fully Transparent)", Float) = 100.0
        _FadeNear("Fade Near (Fully Opaque)", Float) = 20.0
        _TubeRadius("Virtual Tube Radius", Float) = 10.0
        
        [Header(Render State)]
        [Enum(UnityEngine.Rendering.BlendMode)] _SrcBlend("Src Blend", Float) = 5 // SrcAlpha
        [Enum(UnityEngine.Rendering.BlendMode)] _DstBlend("Dst Blend", Float) = 10 // OneMinusSrcAlpha
        [Enum(Off, 0, On, 1)] _ZWrite("Z Write", Float) = 0
        [Enum(Front, 0, Back, 1, Off, 2)] _CullMode("Cull Mode", Float) = 1 // Front (Inside)
    }

    SubShader
    {
        Tags 
        { 
            "RenderPipeline" = "UniversalPipeline"
            "RenderType" = "Transparent" 
            "Queue" = "Transparent-300" 
            "UniversalMaterialType" = "Unlit"
            "IgnoreProjector" = "True"
        }

        Blend [_SrcBlend] [_DstBlend]
        ZWrite [_ZWrite]
        Cull [_CullMode] // Default Cull Front to see inside the tube
        
        Pass
        {
            Name "ForwardOnly"
            Tags { "LightMode" = "UniversalForwardOnly" }

            HLSLPROGRAM
            #pragma target 4.5
            #pragma prefer_hlslcc gles
            #pragma multi_compile_instancing
            #pragma multi_compile_fog

            #pragma vertex vert
            #pragma fragment frag

            #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;
                float3 positionWS   : TEXCOORD0;
                float3 positionOS   : TEXCOORD1;
                half   fogFactor    : TEXCOORD3;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            CBUFFER_START(UnityPerMaterial)
                half4 _Color0;
                float4 _PatternSize;
                float  _GridDensity;
                float  _BaseSpeed;
                float  _TimeAngle;
                float  _StepA;
                float  _StepB;
                float  _SeamRotation;
                float  _SeamFadeWidth;
                float  _SeamFadeSmoothness;
                float  _FadeFar;
                float  _FadeNear;
                float  _TubeRadius;
            CBUFFER_END

            // -------------------------------------
            // 极限优化工具库组 (无三角函数，全MAD指令)
            
            // Fast 2D Hash (纯乘加与小数截断，干掉 sin)
            float2 FastHash22(float2 p)
            {
                float3 p3 = frac(float3(p.xyx) * float3(0.1031, 0.1030, 0.0973));
                p3 += dot(p3, p3.yzx + 33.33);
                return frac((p3.xx + p3.yz) * p3.zy);
            }

            // Extreme Optimized 4-Tap Voronoi for Mobile (从9次循环砍至4次)
            float VoronoiDistanceFast(float2 v, float t)
            {
                float2 n = floor(v);
                float2 f = frac(v);
                
                // 象限锚定：算出像素所处方格的偏向，完美剔除背面5个不可能相邻的远格
                float2 mg = step(0.5, f); 
                
                float minDist = 8.0;

                UNITY_UNROLL
                for (int j = 0; j <= 1; j++)
                {
                    UNITY_UNROLL
                    for (int i = 0; i <= 1; i++)
                    {
                        // 检索偏向象限的核心 4 个格子
                        float2 g = mg + float2(i - 1.0, j - 1.0);
                        
                        float2 hash = FastHash22(n + g);
                        
                        // 剔除昂贵的 sin 并换用平滑三角波：
                        // t * 0.1591549 即相当于 t / (2*PI) 把时间归一化到周期
                        float2 phase = frac(t * 0.1591549 + hash);
                        float2 tri = abs(phase * 2.0 - 1.0);       // 线性三角波 1 -> 0 -> 1
                        float2 o = tri * tri * (3.0 - 2.0 * tri);  // 光滑三次曲线，模拟 sin 的柔顺运动
                        
                        float2 r = f - g - o;
                        
                        // Manhattan 曼哈顿距离
                        float d = 0.5 * (abs(r.x) + abs(r.y));
                        minDist = min(minDist, d);
                    }
                }
                return minDist;
            }

            // -------------------------------------
            // Vertex Shader
            Varyings vert(Attributes input)
            {
                Varyings output = (Varyings)0;
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.positionCS = vertexInput.positionCS;
                output.positionWS = vertexInput.positionWS;
                output.positionOS = input.positionOS.xyz;
                output.fogFactor  = ComputeFogFactor(vertexInput.positionCS.z);

                return output;
            }

            // -------------------------------------
            // Fragment Shader
            half4 frag(Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);

                // ==========================================
                // 1. Cylindrical Mapping & Seam Control
                // ==========================================
                // Calculate angle around the Z-axis in object space. atan2 returns [-PI, PI].
                float rawAngle = atan2(input.positionOS.y, input.positionOS.x);

                // Rotate the seam mechanically
                float angleOffset = _SeamRotation * (3.14159265 / 180.0);
                float angle = rawAngle + angleOffset;

                // Wrap angle to [-PI, PI] to keep math bounded 
                if(angle > 3.14159265) angle -= 6.2831853;
                if(angle < -3.14159265) angle += 6.2831853;

                // Derive distance to the seam (seam is at absolute PI or -PI)
                float distToSeam = 3.14159265 - abs(angle);
                
                // Seam alpha fading calculation
                float endFade = _SeamFadeWidth * 3.14159265;
                float startFade = endFade * (1.0 - _SeamFadeSmoothness);
                float seamFadeMask = smoothstep(startFade, endFade + 0.0001, distToSeam);

                // Convert adjusted angle to U coordinate
                float u = angle * _TubeRadius;
                
                // V is driven by Object Z scaled by World Scale to maintain seamless tiling and resist rotation stretching
                float scaleZ = length(float3(unity_ObjectToWorld[0].z, unity_ObjectToWorld[1].z, unity_ObjectToWorld[2].z));
                float v = input.positionOS.z * scaleZ;

                float2 cylindricalUV = float2(u, v);

                // Density Multiplier
                float density = max(_GridDensity, 0.0001);
                float2 sizeDivisor = max(_PatternSize.xy, float2(0.0001, 0.0001)) / density;
                
                float2 scaledUV = cylindricalUV / sizeDivisor;

                // Rotate 45 degrees
                float c = 0.707106; 
                float s = 0.707106;
                float2 rotatedUV = mul(scaledUV, float2x2(c, -s, s, c));

                // Time driven animation (Base Time + Phase Offset)
                float t = _TimeParameters.x * _BaseSpeed + _TimeAngle;
                
                // [TA 极限计算压缩] 使用 4-Tap、零三角函数的极简数学方法，保持无限分辨率。
                float voronoiV = VoronoiDistanceFast(rotatedUV, t);

                // Anti-aliased border mask computation
                float fw = fwidth(voronoiV);
                float edge1 = smoothstep(_StepA - fw, _StepA + fw, voronoiV);
                float edge2 = smoothstep(_StepB - fw, _StepB + fw, voronoiV);
                float gridAlphaMask = edge2 - edge1;

                half3 gridColor = _Color0.rgb;
                half  gridAlpha = gridAlphaMask * _Color0.a;

                // ==========================================
                // 2. Distance Fade (Far = Transparent, Near = Opaque)
                // ==========================================
                float distToCam = distance(GetCameraPositionWS(), input.positionWS);
                
                // If distToCam is between _FadeFar and _FadeNear, smoothly transition
                // When dist = _FadeFar, fadeMask = 0 (Transparent)
                // When dist = _FadeNear, fadeMask = 1 (Opaque)
                float rawFade = (distToCam - _FadeFar) / (_FadeNear - _FadeFar + 0.0001);
                float fadeMask = saturate(rawFade);

                // Multiply the alpha by our camera distance fade AND seam smooth fade
                gridAlpha *= fadeMask * seamFadeMask;

                // Apply URP Fog
                gridColor = MixFog(gridColor, input.fogFactor);

                return half4(gridColor, gridAlpha);
            }
            ENDHLSL
        }
    }
    FallBack "Hidden/Universal Render Pipeline/FallbackError"
}