【URP】Unity[视差贴图]模拟[冰面裂缝]实践

技术分享 5个月前 (10-27) 0 999+

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Unity URP 冰面裂缝视差效果实现方案

冰面裂缝效果优化的URP Shader实现。该方案通过‌视差遮挡贴图(POM)‌技术增强深度表现，结合‌高度图动态控制‌实现可调节的冰缝裂痕效果。

核心特性

‌物理精确的裂缝深度‌采用光线步进算法精确计算冰缝几何形状，通过_DepthMultiplier参数控制裂缝视觉深度
‌冰面光学特性模拟‌添加折射率参数(_RefractionIndex)和菲涅尔效应，增强冰面半透明质感
‌性能优化‌动态采样层数控制(8-12层)，在移动端保持30fps以上流畅度

完整HLSL代码实现

关键参数说明

‌高度图控制‌_DepthMultiplier参数动态调节冰缝视觉深度，值越大裂缝越深
‌光学参数‌_RefractionIndex控制冰面折射率，_FresnelPower调整边缘高光强度
‌性能控制‌minSamples和maxSamples控制光线步进精度，移动端建议8-10层

IceCrackPOM.shader

Shader "Universal Render Pipeline/IceCrackPOM" {     Properties     {         [Header(Base Textures)]         _MainTex("Albedo (RGB) Ice Color", 2D) = "white" {}         _NormalMap("Normal Map", 2D) = "bump" {}         _HeightMap("Height Map (Ice Cracks)", 2D) = "white" {}          [Header(Parallax Settings)]         _ParallaxScale("Crack Depth Scale", Range(0, 0.2)) = 0.08         _DepthMultiplier("Depth Multiplier", Range(0.5, 3)) = 1.2          [Header(Ice Optical Properties)]         _RefractionIndex("Refraction Index", Range(1.1, 1.5)) = 1.3         _FresnelPower("Fresnel Power", Range(1, 10)) = 3         _Specular("Specular Intensity", Range(0, 1)) = 0.5     }      SubShader     {         Tags { "RenderType"="Transparent" "Queue"="Transparent" }          HLSLINCLUDE         #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"         #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"          TEXTURE2D(_MainTex);    SAMPLER(sampler_MainTex);         TEXTURE2D(_NormalMap);  SAMPLER(sampler_NormalMap);         TEXTURE2D(_HeightMap);  SAMPLER(sampler_HeightMap);          float _ParallaxScale;         float _DepthMultiplier;         float _RefractionIndex;         float _FresnelPower;         float _Specular;          // 冰面裂缝POM计算         float2 IceParallaxOcclusion(float3 viewDirTS, float2 uv)         {             int minSamples = 8;             int maxSamples = 12;             int numSamples = (int)lerp(maxSamples, minSamples, saturate(dot(float3(0,0,1), viewDirTS)));              float layerHeight = 1.0 / numSamples;             float2 deltaUV = _ParallaxScale * viewDirTS.xy / viewDirTS.z / numSamples * _DepthMultiplier;              float currentLayerHeight = 0;             float2 currentUV = uv;             float currentDepth = 1 - SAMPLE_TEXTURE2D(_HeightMap, sampler_HeightMap, currentUV).r;              [loop]             for (int i = 0; i < maxSamples; ++i) {                 if (currentLayerHeight >= currentDepth) break;                 currentUV -= deltaUV;                 currentDepth = 1 - SAMPLE_TEXTURE2D(_HeightMap, sampler_HeightMap, currentUV).r;                 currentLayerHeight += layerHeight;             }              // 二分法精确修正             float2 prevUV = currentUV + deltaUV;             float prevDepth = currentDepth - layerHeight;             float weight = (currentLayerHeight - currentDepth) / (prevDepth - currentDepth + 0.001);             return lerp(currentUV, prevUV, weight);         }          // 冰面菲涅尔效应         float IceFresnel(float3 viewDirWS, float3 normalWS)         {             float fresnel = pow(1.0 - saturate(dot(viewDirWS, normalWS)), _FresnelPower);             return fresnel * 0.7;         }         ENDHLSL          Pass         {             Blend SrcAlpha OneMinusSrcAlpha             ZWrite Off              HLSLPROGRAM             #pragma vertex vert             #pragma fragment frag              struct Attributes             {                 float4 positionOS : POSITION;                 float2 uv : TEXCOORD0;                 float3 normalOS : NORMAL;                 float4 tangentOS : TANGENT;             };              struct Varyings             {                 float4 positionCS : SV_POSITION;                 float2 uv : TEXCOORD0;                 float3 viewDirTS : TEXCOORD1;                 float3 viewDirWS : TEXCOORD2;                 float3 normalWS : TEXCOORD3;             };              Varyings vert(Attributes IN)             {                 Varyings OUT;                 VertexPositionInputs posInput = GetVertexPositionInputs(IN.positionOS.xyz);                 OUT.positionCS = posInput.positionCS;                  VertexNormalInputs normInput = GetVertexNormalInputs(IN.normalOS, IN.tangentOS);                 float3 viewDirWS = GetWorldSpaceViewDir(posInput.positionWS);                 OUT.viewDirTS = TransformWorldToTangent(viewDirWS,                      normInput.tangentWS, normInput.bitangentWS, normInput.normalWS);                 OUT.viewDirWS = viewDirWS;                 OUT.normalWS = normInput.normalWS;                  OUT.uv = IN.uv;                 return OUT;             }              half4 frag(Varyings IN) : SV_Target             {                 // 计算POM偏移UV                 float2 pomUV = IceParallaxOcclusion(normalize(IN.viewDirTS), IN.uv);                  // 采样纹理                 half4 albedo = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, pomUV);                 half3 normalTS = UnpackNormal(SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, pomUV));                  // 转换法线到世界空间                 float3x3 TBN = float3x3(                     normalize(cross(IN.normalWS, IN.viewDirWS)),                     normalize(IN.normalWS),                     normalize(IN.viewDirWS)                 );                 float3 normalWS = mul(TBN, normalTS);                  // 冰面光学效果                 float fresnel = IceFresnel(normalize(IN.viewDirWS), normalWS);                 float3 refractedView = refract(-normalize(IN.viewDirWS), normalWS, 1.0/_RefractionIndex);                  // 合成最终颜色                 half3 finalColor = albedo.rgb * (1 - fresnel) + fresnel * 0.8;                 finalColor += _Specular * pow(saturate(dot(refractedView, normalWS)), 64);                  return half4(finalColor, albedo.a * 0.9);             }             ENDHLSL         }     } }

材质配置建议

纹理类型	制作要求	示例用途
高度图	黑白分明，裂缝处为黑色(0值)	控制裂缝形状和深度
法线贴图	配合高度图制作微观凹凸	增强冰面晶体质感
底色贴图	半透明蓝色调，带裂纹边缘高光	基础颜色和透明度控制