Add optional tint to dielectric material/BxDF

src/pbrt/bxdfs.cpp

@@ -88,8 +88,8 @@ SampledSpectrum DielectricInterfaceBxDF::f(Vector3f wo, Vector3f wi,
             return SampledSpectrum(0.);
         wh = Normalize(wh);
         Float F = FrDielectric(Dot(wi, FaceForward(wh, Vector3f(0, 0, 1))), eta);
-        return SampledSpectrum(mfDistrib.D(wh) * mfDistrib.G(wo, wi) * F /
-                               (4 * cosTheta_i * cosTheta_o));
+        return tint * SampledSpectrum(mfDistrib.D(wh) * mfDistrib.G(wo, wi) * F /
+                                      (4 * cosTheta_i * cosTheta_o));
 
     } else {
         // Compute transmission at non-delta dielectric interface
@@ -112,7 +112,8 @@ SampledSpectrum DielectricInterfaceBxDF::f(Vector3f wo, Vector3f wi,
         Float F = FrDielectric(Dot(wo, wh), eta);
         Float sqrtDenom = Dot(wo, wh) + etap * Dot(wi, wh);
         Float factor = (mode == TransportMode::Radiance) ? Sqr(1 / etap) : 1;
-        return SampledSpectrum((1 - F) * factor *
+        return tint *
+               SampledSpectrum((1 - F) * factor *
                                std::abs(mfDistrib.D(wh) * mfDistrib.G(wo, wi) *
                                         AbsDot(wi, wh) * AbsDot(wo, wh) /
                                         (cosTheta_i * cosTheta_o * Sqr(sqrtDenom))));
@@ -137,7 +138,7 @@ pstd::optional<BSDFSample> DielectricInterfaceBxDF::Sample_f(
         if (uc < pr / (pr + pt)) {
             // Sample perfect specular reflection at interface
             Vector3f wi(-wo.x, -wo.y, wo.z);
-            SampledSpectrum fr(R / AbsCosTheta(wi));
+            SampledSpectrum fr(tint * R / AbsCosTheta(wi));
             return BSDFSample(fr, wi, pr / (pr + pt), BxDFFlags::SpecularReflection);
 
         } else {
@@ -153,7 +154,7 @@ pstd::optional<BSDFSample> DielectricInterfaceBxDF::Sample_f(
             if (tir)
                 return {};
 
-            SampledSpectrum ft(T / AbsCosTheta(wi));
+            SampledSpectrum ft(tint * T / AbsCosTheta(wi));
             // Account for non-symmetry with transmission to different medium
             if (mode == TransportMode::Radiance)
                 ft /= Sqr(etap);
@@ -285,8 +286,8 @@ Float DielectricInterfaceBxDF::PDF(Vector3f wo, Vector3f wi, TransportMode mode,
 }
 
 std::string DielectricInterfaceBxDF::ToString() const {
-    return StringPrintf("[ DielectricInterfaceBxDF eta: %f mfDistrib: %s ]", eta,
-                        mfDistrib.ToString());
+    return StringPrintf("[ DielectricInterfaceBxDF eta: %f mfDistrib: %s tint: %s ]", eta,
+                        mfDistrib.ToString(), tint);
 }
 
 std::string ThinDielectricBxDF::ToString() const {

src/pbrt/bxdfs.h

@@ -197,8 +197,9 @@ class DielectricInterfaceBxDF {
     // DielectricInterfaceBxDF Public Methods
     DielectricInterfaceBxDF() = default;
     PBRT_CPU_GPU
-    DielectricInterfaceBxDF(Float eta, const TrowbridgeReitzDistribution &mfDistrib)
-        : eta(eta == 1 ? 1.001 : eta), mfDistrib(mfDistrib) {}
+    DielectricInterfaceBxDF(Float eta, SampledSpectrum tint,
+                            const TrowbridgeReitzDistribution &mfDistrib)
+        : eta(eta == 1 ? 1.001 : eta), tint(tint), mfDistrib(mfDistrib) {}
 
     PBRT_CPU_GPU
     BxDFFlags Flags() const {
@@ -229,6 +230,7 @@ class DielectricInterfaceBxDF {
   private:
     // DielectricInterfaceBxDF Private Members
     Float eta;
+    SampledSpectrum tint;
     TrowbridgeReitzDistribution mfDistrib;
 };
 
@@ -266,7 +268,7 @@ class ThinDielectricBxDF {
             return {};
 
         if (uc < pr / (pr + pt)) {
-            // Sample perfect specular reflection at interface
+            // Sample perfect specular reflection at thin dielectric interface
             Vector3f wi(-wo.x, -wo.y, wo.z);
             SampledSpectrum fr(R / AbsCosTheta(wi));
             return BSDFSample(fr, wi, pr / (pr + pt), BxDFFlags::SpecularReflection);

src/pbrt/materials.cpp

@@ -30,8 +30,8 @@ namespace pbrt {
 std::string DielectricMaterial::ToString() const {
     return StringPrintf("[ DielectricMaterial displacement: %s uRoughness: %s "
                         "vRoughness: %s etaF: %s "
-                        "etaS: %s remapRoughness: %s ]",
-                        displacement, uRoughness, vRoughness, etaF, etaS,
+                        "etaS: %s tint: %s remapRoughness: %s ]",
+                        displacement, uRoughness, vRoughness, etaF, etaS, tint,
                         remapRoughness);
 }
 
@@ -60,8 +60,11 @@ DielectricMaterial *DielectricMaterial::Create(
         parameters.GetFloatTextureOrNull("displacement", alloc);
     bool remapRoughness = parameters.GetOneBool("remaproughness", true);
 
+    SpectrumTextureHandle tint =
+        parameters.GetSpectrumTextureOrNull("tint", SpectrumType::Albedo, alloc);
     return alloc.new_object<DielectricMaterial>(uRoughness, vRoughness, etaF, etaS,
-                                                displacement, normalMap, remapRoughness);
+                                                displacement, normalMap, tint,
+                                                remapRoughness);
 }
 
 // ThinDielectricMaterial Method Definitions

src/pbrt/materials.h

@@ -142,13 +142,14 @@ class DielectricMaterial {
     DielectricMaterial(FloatTextureHandle uRoughness, FloatTextureHandle vRoughness,
                        FloatTextureHandle etaF, SpectrumTextureHandle etaS,
                        FloatTextureHandle displacement, Image *normalMap,
-                       bool remapRoughness)
+                       SpectrumTextureHandle tint, bool remapRoughness)
         : displacement(displacement),
           normalMap(normalMap),
           uRoughness(uRoughness),
           vRoughness(vRoughness),
           etaF(etaF),
           etaS(etaS),
+          tint(tint),
           remapRoughness(remapRoughness) {
         CHECK((bool)etaF ^ (bool)etaS);
     }
@@ -157,7 +158,7 @@ class DielectricMaterial {
 
     template <typename TextureEvaluator>
     PBRT_CPU_GPU bool CanEvaluateTextures(TextureEvaluator texEval) const {
-        return texEval.CanEvaluate({etaF, uRoughness, vRoughness}, {etaS});
+        return texEval.CanEvaluate({etaF, uRoughness, vRoughness}, {etaS, tint});
     }
 
     PBRT_CPU_GPU
@@ -200,7 +201,8 @@ class DielectricMaterial {
         TrowbridgeReitzDistribution distrib(urough, vrough);
 
         // Return BSDF for dielectric material
-        *bxdf = DielectricInterfaceBxDF(eta, distrib);
+        SampledSpectrum t = tint ? texEval(tint, ctx, lambda) : SampledSpectrum(1.f);
+        *bxdf = DielectricInterfaceBxDF(eta, t, distrib);
         return BSDF(ctx.wo, ctx.n, ctx.ns, ctx.dpdus, bxdf);
     }
 
@@ -210,6 +212,7 @@ class DielectricMaterial {
     Image *normalMap;
     FloatTextureHandle uRoughness, vRoughness, etaF;
     SpectrumTextureHandle etaS;
+    SpectrumTextureHandle tint;
     bool remapRoughness;
 };
 
@@ -629,7 +632,7 @@ class CoatedDiffuseMaterial {
         Float gg = Clamp(texEval(g, ctx), -1, 1);
 
         *bxdf =
-            CoatedDiffuseBxDF(DielectricInterfaceBxDF(e, distrib),
+            CoatedDiffuseBxDF(DielectricInterfaceBxDF(e, SampledSpectrum(1.f), distrib),
                               IdealDiffuseBxDF(r), thick, a, gg, config);
         return BSDF(ctx.wo, ctx.n, ctx.ns, ctx.dpdus, bxdf);
     }
@@ -731,7 +734,7 @@ class CoatedConductorMaterial {
         Float gg = Clamp(texEval(g, ctx), -1, 1);
 
         *bxdf = CoatedConductorBxDF(
-            DielectricInterfaceBxDF(ieta, interfaceDistrib),
+            DielectricInterfaceBxDF(ieta, SampledSpectrum(1.f), interfaceDistrib),
             ConductorBxDF(conductorDistrib, ce, ck), thick, a, gg, config);
         return BSDF(ctx.wo, ctx.n, ctx.ns, ctx.dpdus, bxdf);
     }
@@ -817,7 +820,7 @@ class SubsurfaceMaterial {
         TrowbridgeReitzDistribution distrib(urough, vrough);
 
         // Initialize _bsdf_ for smooth or rough dielectric
-        *bxdf = DielectricInterfaceBxDF(eta, distrib);
+        *bxdf = DielectricInterfaceBxDF(eta, SampledSpectrum(1.f), distrib);
         return BSDF(ctx.wo, ctx.n, ctx.ns, ctx.dpdus, bxdf);
     }