【URP】Unity[视差贴图]模拟[风格化地形]实践

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【从UnityURP开始探索游戏渲染】专栏-直达

陡峭视差贴图(Steep Parallax Mapping)实现原理

陡峭视差贴图通过‌分层深度比较‌和‌动态UV偏移‌技术增强岩石表面立体感.

‌视角自适应分层采样‌

根据视线与表面法线的夹角动态分配采样层数（平视视角增加至12层，俯视视角减少至5层），解决标准视差贴图在平视角度下的失真问题

‌深度图梯度修正‌

引入_LayerBias参数（推荐值0.2-0.4）调整UV偏移量计算公式，避免陡峭区域出现采样断裂：

$Delta UV=frac{ParallaxScale cdot ViewDir_{xy}}{(ViewDir_z+LayerBias) cdot LayerCount}$

‌风格化深度增强‌

在最终插值阶段使用pow(weight,2)强化轮廓对比度，配合ramp贴图实现卡通化光影过渡效果

URP HLSL完整实现代码

关键特性说明

‌动态层数优化‌：通过lerp(_MaxLayers, _MinLayers, saturate(dot(float3(0,0,1), viewDirTS)))实现平视视角自动增加采样精度
‌抗失真处理‌：_LayerBias参数修正陡峭表面的UV偏移计算，避免采样断裂
‌风格化增强‌：ramp贴图控制光影过渡，边缘光强化轮廓立体感

StylizedRockParallax.shader

Shader "Universal Render Pipeline/StylizedRockParallax" {     Properties     {         [Header(Base Textures)]         _MainTex("Albedo (RGB)", 2D) = "white" {}         _NormalMap("Normal Map", 2D) = "bump" {}         _HeightMap("Height Map", 2D) = "white" {}         _RampTex("Stylized Ramp", 2D) = "white" {}          [Header(Parallax Settings)]         _ParallaxScale("Depth Scale", Range(0, 0.15)) = 0.08         _LayerBias("Layer Bias", Range(0.1, 0.5)) = 0.3         _MinLayers("Min Layers", Int) = 5         _MaxLayers("Max Layers", Int) = 12          [Header(Stylized Lighting)]         _RimPower("Rim Power", Range(1, 10)) = 3         _ShadowTint("Shadow Tint", Color) = (0.3,0.3,0.4,1)     }      SubShader     {         Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" }          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);         TEXTURE2D(_RampTex);    SAMPLER(sampler_RampTex);          float _ParallaxScale;         float _LayerBias;         int _MinLayers, _MaxLayers;         float _RimPower;         float4 _ShadowTint;          // 陡峭视差映射核心算法         float2 SteepParallaxMapping(float3 viewDirTS, float2 uv)         {             // 动态层数计算（平视视角增加层数）             int numLayers = (int)lerp(_MaxLayers, _MinLayers, saturate(dot(float3(0,0,1), viewDirTS)));             float layerHeight = 1.0 / numLayers;             float2 deltaUV = _ParallaxScale * viewDirTS.xy / (viewDirTS.z + _LayerBias) / numLayers;              // 光线步进初始化             float currentLayerHeight = 0;             float2 currentUV = uv;             float currentDepth = 1 - SAMPLE_TEXTURE2D(_HeightMap, sampler_HeightMap, currentUV).r;              // 分层深度检测             [loop]             for (int i = 0; i < _MaxLayers; ++i) {                 if (currentLayerHeight >= currentDepth) break;                 currentUV -= deltaUV;                 currentDepth = 1 - SAMPLE_TEXTURE2D(_HeightMap, sampler_HeightMap, currentUV).r;                 currentLayerHeight += layerHeight;             }              // 风格化插值修正             float2 prevUV = currentUV + deltaUV;             float prevDepth = currentDepth - layerHeight;             float weight = pow((currentLayerHeight - currentDepth) / (prevDepth - currentDepth + 0.001), 2);             return lerp(currentUV, prevUV, saturate(weight * 1.5));         }          // 风格化光照计算         half3 StylizedShading(float3 normalWS, float3 viewDirWS, float NdotL)         {             float rim = pow(1 - saturate(dot(normalWS, viewDirWS)), _RimPower);             float2 rampUV = float2(NdotL * 0.5 + 0.5, 0.5);             half3 rampColor = SAMPLE_TEXTURE2D(_RampTex, sampler_RampTex, rampUV).rgb;             return lerp(rampColor * _ShadowTint.rgb, rampColor, saturate(NdotL + rim));         }         ENDHLSL          Pass         {             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 normalWS : TEXCOORD2;                 float3 viewDirWS : TEXCOORD3;                 float4 shadowCoord : TEXCOORD4;             };              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.normalWS = normInput.normalWS;                 OUT.viewDirWS = viewDirWS;                 OUT.shadowCoord = GetShadowCoord(posInput);                 OUT.uv = IN.uv;                 return OUT;             }              half4 frag(Varyings IN) : SV_Target             {                 // 计算陡峭视差UV                 float2 parallaxUV = SteepParallaxMapping(normalize(IN.viewDirTS), IN.uv);                  // 采样纹理                 half4 albedo = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, parallaxUV);                 half3 normalTS = UnpackNormal(SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, parallaxUV));                  // 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);                  // 光照计算                 Light mainLight = GetMainLight(IN.shadowCoord);                 float NdotL = saturate(dot(normalWS, mainLight.direction));                 half3 lighting = StylizedShading(normalWS, normalize(IN.viewDirWS), NdotL);                  return half4(albedo.rgb * lighting * mainLight.color, 1);             }             ENDHLSL         }     } }

材质配置

参数组合	风格化效果
`_ParallaxScale=0.05` + `_RimPower=5`	轻度凹凸+柔和边缘光
`_ParallaxScale=0.1` + `_LayerBias=0.4`	强烈凹凸+抗失真处理
`_ShadowTint=(0.4,0.2,0.6)`	紫色调阴影增强风格化表现