源码 / Ch12/ClearCoat.shader
Ch12/ClearCoat.shader
// 清漆（Clear Coat）：在基础 GGX 材质上再盖一层透明的电介质 GGX。 // 两层之间的能量分配、折射对底层的影响，是本案例要讲清的重点。 Shader "Cookbook/Ch12/ClearCoat" { Properties { [MainColor] _BaseColor ("Base Color", Color) = (0.6, 0.04, 0.03, 1) _Metallic ("Metallic", Range(0, 1)) = 0.6 _Smoothness ("Base Smoothness", Range(0, 1)) = 0.45 [Header(Flakes)] _FlakeDensity ("Flake Density (cells per UV)", Float) = 600 _FlakeStrength ("Flake Normal Strength", Range(0, 1)) = 0.35 [Header(Clear Coat)] _CoatMask ("Coat Mask", Range(0, 1)) = 1 _CoatSmoothness ("Coat Smoothness", Range(0, 1)) = 0.95 [Toggle] _CoatEnergy ("Energy Attenuation (1 - Fc)", Float) = 1 [Toggle] _CoatAffectBase ("Coat Modifies Base (IOR 1.5)", Float) = 1 } SubShader { Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" "Queue"="Geometry" } HLSLINCLUDE #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl" #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/CommonMaterial.hlsl" CBUFFER_START(UnityPerMaterial) half4 _BaseColor; half _Metallic, _Smoothness; float _FlakeDensity; half _FlakeStrength; half _CoatMask, _CoatSmoothness, _CoatEnergy, _CoatAffectBase; CBUFFER_END ENDHLSL Pass { Name "ForwardLit" Tags { "LightMode"="UniversalForwardOnly" } HLSLPROGRAM #pragma target 3.5 #pragma vertex Ch12Vert #pragma fragment frag #pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN #pragma multi_compile _ _ADDITIONAL_LIGHTS #pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS #pragma multi_compile_fragment _ _SHADOWS_SOFT _SHADOWS_SOFT_LOW _SHADOWS_SOFT_MEDIUM _SHADOWS_SOFT_HIGH #pragma multi_compile_fragment _ _REFLECTION_PROBE_BLENDING #pragma multi_compile_fragment _ _REFLECTION_PROBE_BOX_PROJECTION #pragma multi_compile_fragment _ _LIGHT_COOKIES #pragma multi_compile _ _FORWARD_PLUS #pragma multi_compile_fog #pragma multi_compile_instancing #include "Assets/Cookbook/Ch12/Ch12Common.hlsl" struct MaterialCtx { float3 N, V; float3 flakeN; // 带金属片扰动的底层法线 float3 diffuse, f0; float aBase; // 底层 α（可能已被清漆修正） float aCoat; // 清漆层 α float coatMask; float coatFv; // 清漆在视线方向的菲涅尔，用来衰减底层 }; half3 ShadeOneLight(MaterialCtx m, Light light) { float3 L = light.direction; float3 H = normalize(m.V + L); float NoL = saturate(dot(m.N, L)); float NoV = max(dot(m.N, m.V), 1e-4); float NoH = saturate(dot(m.N, H)); float VoH = saturate(dot(m.V, H)); // 底层：漫反射 + 金属片法线下的 GGX float3 baseBRDF = m.diffuse * ADV_INV_PI + AdvSpecularGGX(m.flakeN, m.V, L, m.aBase, m.f0); // 清漆层：F0 = 0.04 的电介质 GGX，用宏观法线（漆面是平的） float Fc = AdvF_Schlick(0.04, 1.0, VoH); float coatSpec = AdvD_GGX(NoH, m.aCoat) * AdvV_SmithGGX(NoV, NoL, m.aCoat) * Fc; // 能量衰减：被清漆反射掉的那部分光不会再到达底层 float attenuation = lerp(1.0, 1.0 - m.coatMask * m.coatFv, _CoatEnergy); float3 brdf = baseBRDF * attenuation + coatSpec * m.coatMask; return brdf * PI * light.color * (NoL * light.distanceAttenuation * light.shadowAttenuation); } #include "Assets/Cookbook/Ch12/LightLoop.hlsl" // 程序化金属片：把 UV 切成很小的格子，每格一个随机倾斜的法线 float3 Hash33(float3 p) { p = frac(p * float3(0.1031, 0.1030, 0.0973)); p += dot(p, p.yxz + 33.33); return frac((p.xxy + p.yxx) * p.zyx); } float3 FlakeNormal(float2 uv, float3 T, float3 B, float3 N) { float2 cell = floor(uv * _FlakeDensity); float3 r = Hash33(float3(cell, 7.0)) * 2.0 - 1.0; return normalize(N + (r.x * T + r.y * B) * _FlakeStrength); } half4 frag(Varyings i) : SV_Target { UNITY_SETUP_INSTANCE_ID(i); float3 T, B, N; Ch12BuildFrame(i, T, B, N); float3 V = GetWorldSpaceNormalizeViewDir(i.positionWS); float2 screenUV = GetNormalizedScreenSpaceUV(i.positionCS); float NoV = saturate(dot(N, V)); MaterialCtx m; m.N = N; m.V = V; m.flakeN = FlakeNormal(i.uv, T, B, N); m.coatMask = _CoatMask; m.f0 = lerp(0.04, _BaseColor.rgb, _Metallic); m.diffuse = _BaseColor.rgb * (1.0 - _Metallic) * 0.96; float prBase = 1.0 - _Smoothness; float aBase = max(prBase * prBase, 0.002); if (_CoatAffectBase > 0.5) { // ① 折射让底层波瓣变宽：α → 等效 Blinn-Phong 指数，乘 (1/1.5)²，再换回来（与 URP 的做法相同） float ieta = lerp(1.0, 1.0 / 1.5, m.coatMask); float n = 2.0 / (aBase * aBase) - 2.0; aBase = sqrt(2.0 / (n * ieta * ieta + 2.0)); // ② 底层 F0 原本相对空气，现在相对 IOR=1.5 的漆：数值会变小、颜色更饱和 float3 f0Coat = saturate(m.f0 * (m.f0 * 0.526868 + 0.529324) - 0.0482256); m.f0 = lerp(m.f0, f0Coat, m.coatMask); } m.aBase = aBase; float prCoat = 1.0 - _CoatSmoothness; m.aCoat = max(prCoat * prCoat, 0.002); m.coatFv = AdvF_Schlick(0.04, 1.0, NoV); half3 color = AccumulateDirectLighting(m, i.positionWS, screenUV); // 间接光：底层用（修正后的）底层粗糙度，清漆用自己的粗糙度各采一次反射 float prBaseEff = sqrt(m.aBase); float2 AB = AdvEnvBRDFApprox(prBaseEff, saturate(dot(m.flakeN, V))); float3 baseIndirect = SampleSH(N) * m.diffuse + GlossyEnvironmentReflection(reflect(-V, m.flakeN), i.positionWS, prBaseEff, 1.0, screenUV) * (m.f0 * AB.x + AB.y); float2 ABc = AdvEnvBRDFApprox(prCoat, NoV); float3 coatIndirect = GlossyEnvironmentReflection(reflect(-V, N), i.positionWS, prCoat, 1.0, screenUV) * (0.04 * ABc.x + ABc.y); float attenuation = lerp(1.0, 1.0 - m.coatMask * m.coatFv, _CoatEnergy); color += baseIndirect * attenuation + coatIndirect * m.coatMask; color = MixFog(color, i.fogFactor); return half4(color, 1); } ENDHLSL } Pass { Name "ShadowCaster" Tags { "LightMode"="ShadowCaster" } ZWrite On ZTest LEqual ColorMask 0 Cull Back HLSLPROGRAM #pragma vertex ShadowPassVertex #pragma fragment ShadowPassFragment #pragma multi_compile_instancing #pragma multi_compile_vertex _ _CASTING_PUNCTUAL_LIGHT_SHADOW // URP 自带的阴影 Pass 只在 _ALPHATEST_ON 时才读 _BaseMap，其余部分与材质无关，直接复用 #include "Packages/com.unity.render-pipelines.universal/Shaders/ShadowCasterPass.hlsl" ENDHLSL } Pass { Name "DepthOnly" Tags { "LightMode"="DepthOnly" } ZWrite On ColorMask R Cull Back HLSLPROGRAM #pragma vertex DepthOnlyVertex #pragma fragment DepthOnlyFragment #pragma multi_compile_instancing #include "Packages/com.unity.render-pipelines.universal/Shaders/DepthOnlyPass.hlsl" ENDHLSL } Pass { Name "DepthNormals" Tags { "LightMode"="DepthNormals" } ZWrite On Cull Back HLSLPROGRAM #pragma vertex DepthNormalsVertex #pragma fragment DepthNormalsFragment #pragma multi_compile_instancing #include "Packages/com.unity.render-pipelines.universal/Shaders/DepthNormalsPass.hlsl" ENDHLSL } } }