// 薄膜干涉（Iridescence）：肥皂泡、油膜、甲虫壳、回火金属的彩虹色。 // 菲涅尔项 F 被替换成“三层结构的干涉反射率”，其余仍是 GGX。 // （GLSL 版，对应 Ch12/ThinFilm.shader） Shader "Cookbook/Ch12/ThinFilm" { SubShader { Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" "Queue"="Geometry" } GLSLINCLUDE uniform vec4 _ThicknessTex_ST; uniform vec4 _BaseColor; uniform float _BaseF0, _Thickness, _ThicknessVar, _FilmIOR, _Smoothness; uniform sampler2D _ThicknessTex; ENDGLSL Pass { Name "ForwardLit" Tags { "LightMode"="UniversalForwardOnly" } GLSLPROGRAM #pragma shader_feature_local_fragment _FILM_SPECTRAL _FILM_RGB3 _FILM_BELCOUR #include "Ch12/Ch12Common.glsl" #ifdef VERTEX void main() { Ch12Vert(); } #endif #ifdef FRAGMENT float Sq(float x) { return x * x; } #if defined(_FILM_BELCOUR) // ---- 以下移植自 core 包 BSDF.hlsl 的 EvalSensitivity / EvalIridescence（HDRP 用的 Belcour & Barla 2017 实现）---- // HLSL 版直接调用 core 包里的函数，GLSL 版没有这个库，所以把它们原样抄在这里 float IorToFresnel0(float transmittedIor, float incidentIor) { return Sq((transmittedIor - incidentIor) / (transmittedIor + incidentIor)); } float F_Schlick(float f0, float u) { float x = 1.0 - u; float x2 = x * x; return (1.0 - f0) * (x * x2 * x2) + f0; } vec3 F_Schlick(vec3 f0, float u) { float x = 1.0 - u; float x2 = x * x; return (1.0 - f0) * (x * x2 * x2) + f0; } // 在傅里叶空间里求 XYZ 敏感度曲线（高斯拟合），再转到线性 sRGB vec3 EvalSensitivity(float opd, float shift) { float phase = 2.0 * PI * opd * 1e-6; vec3 val = vec3(5.4856e-13, 4.4201e-13, 5.2481e-13); vec3 pos = vec3(1.6810e+06, 1.7953e+06, 2.2084e+06); vec3 var = vec3(4.3278e+09, 9.3046e+09, 6.6121e+09); vec3 xyz = val * sqrt(2.0 * PI * var) * cos(pos * phase + shift) * exp(-var * phase * phase); xyz.x += 9.7470e-14 * sqrt(2.0 * PI * 4.5282e+09) * cos(2.2399e+06 * phase + shift) * exp(-4.5282e+09 * phase * phase); xyz /= 1.0685e-7; // XYZ_2_REC709_MAT（HLSL 按行初始化；GLSL 写成 v * mat3(行0, 行1, 行2)） return xyz * mat3( 3.2409699419, -1.5373831776, -0.4986107603, -0.9692436363, 1.8759675015, 0.0415550574, 0.0556300797, -0.2039769589, 1.0569715142); } // 电介质基底上一层薄膜的反射率 vec3 EvalIridescence(float eta_1, float cosTheta1, float iridescenceThickness, vec3 baseLayerFresnel0) { vec3 I; // 厚度单位是微米，0.5 对应 500nm float Dinc = 3.0 * iridescenceThickness; // 用厚度反推薄膜折射率（HDRP 的“单参数”做法） float eta_2 = mix(2.0, 1.0, iridescenceThickness); float sinTheta2Sq = Sq(eta_1 / eta_2) * (1.0 - Sq(cosTheta1)); float cosTheta2Sq = (1.0 - sinTheta2Sq); if (cosTheta2Sq < 0.0) I = vec3(1.0); // 全反射 else { float cosTheta2 = sqrt(cosTheta2Sq); // 第一个界面 float R0 = IorToFresnel0(eta_2, eta_1); float R12 = F_Schlick(R0, cosTheta1); float T121 = 1.0 - R12; float phi12 = 0.0; float phi21 = PI - phi12; // 第二个界面 vec3 R23 = F_Schlick(baseLayerFresnel0, cosTheta2); float phi23 = 0.0; // 相位差 float OPD = Dinc * cosTheta2; float phi = phi21 + phi23; vec3 R123 = clamp(R12 * R23, 1e-5, 0.9999); vec3 r123 = sqrt(R123); vec3 Rs = Sq(T121) * R23 / (vec3(1.0) - R123); // m = 0 项 vec3 C0 = R12 + Rs; I = C0; // m > 0 项 vec3 Cm = Rs - T121; for (int m = 1; m <= 2; ++m) { Cm *= r123; vec3 Sm = 2.0 * EvalSensitivity(float(m) * OPD, float(m) * phi); I += Cm * Sm; } // 超出色域的颜色可能为负，截到 0 I = max(I, vec3(0.0)); } return I; } #endif //#region film vec3 FilmFresnel(float cosTheta, float thickness) { #if defined(_FILM_RGB3) // 偷懒版：只在 R/G/B 三个代表波长上算一次 Airy 反射率 float sin2 = (1.0 - cosTheta * cosTheta) / (_FilmIOR * _FilmIOR); float opd = 2.0 * _FilmIOR * thickness * sqrt(saturate(1.0 - sin2)); float r12 = -sqrt(AdvF_Schlick(Sq((1.0 - _FilmIOR) / (1.0 + _FilmIOR)), 1.0, cosTheta)); float baseIOR = (1.0 + sqrt(_BaseF0)) / (1.0 - sqrt(min(_BaseF0, 0.99))); float r23 = sign(_FilmIOR - baseIOR) * sqrt(Sq((_FilmIOR - baseIOR) / (_FilmIOR + baseIOR))); return vec3(AdvAiryReflectance(r12, r23, opd, 650.0), AdvAiryReflectance(r12, r23, opd, 532.0), AdvAiryReflectance(r12, r23, opd, 450.0)); #elif defined(_FILM_BELCOUR) // core 包里 HDRP 用的 Belcour & Barla 2017 实现；它的厚度参数是 0~1 的归一化值 return EvalIridescence(1.0, cosTheta, saturate(thickness / 1000.0), vec3(_BaseF0)); #else return AdvThinFilm(cosTheta, thickness, _FilmIOR, _BaseF0); #endif } //#endregion struct MaterialCtx { vec3 N, V; vec3 diffuse; float a, thickness; }; vec3 ShadeOneLight(MaterialCtx m, Light light) { vec3 L = light.direction; vec3 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)); vec3 F = FilmFresnel(VoH, m.thickness); // 用薄膜反射率替换 Schlick vec3 spec = AdvD_GGX(NoH, m.a) * AdvV_SmithGGX(NoV, NoL, m.a) * F; vec3 brdf = m.diffuse * ADV_INV_PI + spec; return brdf * PI * light.color * (NoL * light.distanceAttenuation * light.shadowAttenuation); } #include "Ch12/LightLoop.glsl" void main() { vec3 T, B, N; Ch12BuildFrame(T, B, N); vec3 V = GetWorldSpaceNormalizeViewDir(positionWS); vec2 screenUV = GetNormalizedScreenSpaceUV(gl_FragCoord); float NoV = saturate(dot(N, V)); float tn = texture(_ThicknessTex, TransformTex(uv, _ThicknessTex_ST)).r; MaterialCtx m; m.N = N; m.V = V; m.diffuse = _BaseColor.rgb; m.thickness = max(_Thickness + (tn - 0.5) * 2.0 * _ThicknessVar, 0.0); float pr = 1.0 - _Smoothness; m.a = max(pr * pr, 0.002); vec3 color = AccumulateDirectLighting(m, positionWS, screenUV); // 环境反射同样用薄膜反射率，角度取 N·V；AB.x + AB.y 近似粗糙度带来的能量损失 vec2 AB = AdvEnvBRDFApprox(pr, NoV); color += SampleSH(N) * m.diffuse; color += GlossyEnvironmentReflection(reflect(-V, N), positionWS, pr, 1.0) * FilmFresnel(NoV, m.thickness) * (AB.x + AB.y); color = MixFog(color, fogFactor); fragColor = vec4(color, 1.0); } #endif ENDGLSL } UsePass "Cookbook/Common/SHADOWCASTER" UsePass "Cookbook/Common/DEPTHONLY" UsePass "Cookbook/Common/DEPTHNORMALS" } }