【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
cShader "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 |
【从UnityURP开始探索游戏渲染】专栏-直达
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