#5 Realistic Transparency

CMakeLists.txt

@@ -18,6 +18,8 @@ endif ()
 set (SOURCE_BRDFS
   src/BRDFs/BRDF.cpp
   src/BRDFs/BRDF.h
+  src/BRDFs/FresnelReflector.cpp
+  src/BRDFs/FresnelReflector.h
   src/BRDFs/GlossySpecular.cpp
   src/BRDFs/GlossySpecular.h
   src/BRDFs/Lambertian.cpp
@@ -29,6 +31,8 @@ set (SOURCE_BRDFS
 set (SOURCE_BTDFS
   src/BTDFs/BTDF.cpp
   src/BTDFs/BTDF.h
+  src/BTDFs/FresnelTransmitter.cpp
+  src/BTDFs/FresnelTransmitter.h
   src/BTDFs/PerfectTransmitter.cpp
   src/BTDFs/PerfectTransmitter.h
 )

src/BRDFs/FresnelReflector.cpp

@@ -0,0 +1,69 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#include "FresnelReflector.h"
+
+#include <cmath>
+#include <utility>
+
+#include "../Utilities/ShadeRec.h"
+#include "../Utilities/Vector3D.h"
+
+FresnelReflector::FresnelReflector(const FresnelReflector& fr) : BRDF(fr), eta_in(fr.eta_in), eta_out(fr.eta_out) {}
+
+FresnelReflector::FresnelReflector(FresnelReflector&& fr) noexcept : BRDF(std::move(fr)), eta_in(std::exchange(fr.eta_in, 1.0f)), eta_out(std::exchange(fr.eta_out, 1.0f)) {}
+
+FresnelReflector& FresnelReflector::operator=(const FresnelReflector& fr) {
+    FresnelReflector::operator=(fr);
+    eta_in = fr.eta_in;
+    eta_out = fr.eta_out;
+
+    return *this;
+}
+
+FresnelReflector& FresnelReflector::operator=(FresnelReflector&& fr) noexcept {
+    FresnelReflector::operator=(fr);
+    eta_in = std::exchange(fr.eta_in, 1.0f);
+    eta_out = std::exchange(fr.eta_out, 1.0f);
+
+    return *this;
+}
+
+FresnelReflector* FresnelReflector::clone() const { return new FresnelReflector(*this); }
+
+RGBColor FresnelReflector::sample_f(const ShadeRec& sr, const Vector3D& wo, Vector3D& wr) const {
+    float ndotwo = sr.normal * wo;
+    wr = -wo + 2.0f * sr.normal * ndotwo;
+    return fresnel(sr) * RGBColor::white / fabs(sr.normal * wr);
+}
+
+float FresnelReflector::fresnel(const ShadeRec& sr) const {
+    Normal normal(sr.normal);
+    float ndotd = -normal * sr.ray.d;
+    float eta;
+
+    if (ndotd < 0.0f) {
+        normal = -normal;
+        eta = eta_out / eta_in;
+    } else {
+        eta = eta_in / eta_out;
+    }
+
+    float cos_theta_i = -normal * sr.ray.d;
+    float temp = 1.0f - (1.0f - cos_theta_i * cos_theta_i) / (eta * eta);
+    float cos_theta_t = sqrt(1.0f - (1.0f - cos_theta_i * cos_theta_i) / (eta * eta));
+    float r_parallel = (eta * cos_theta_i - cos_theta_t) / (eta * cos_theta_i + cos_theta_t);
+    float r_perpendicular = (cos_theta_i - eta * cos_theta_t) / (cos_theta_i + eta * cos_theta_t);
+    float kr = 0.5f * (r_parallel * r_parallel + r_perpendicular * r_perpendicular);
+
+    return kr;
+}

src/BRDFs/FresnelReflector.h

@@ -0,0 +1,56 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#ifndef __FRESNEL_REFLECTOR__
+#define __FRESNEL_REFLECTOR__
+
+class ShadeRec;
+class Vector;
+
+#include "BRDF.h"
+
+class FresnelReflector : public BRDF {
+public:
+
+    FresnelReflector() = default;
+
+    ~FresnelReflector() = default;
+
+    FresnelReflector(const FresnelReflector& fr);
+
+    FresnelReflector(FresnelReflector&& fr) noexcept;
+
+    FresnelReflector& operator=(const FresnelReflector& fr);
+
+    FresnelReflector& operator=(FresnelReflector&& fr) noexcept;
+
+    FresnelReflector* clone() const override;
+
+    void set_eta_in(const float eta);
+
+    void set_eta_out(const float eta);
+
+    RGBColor sample_f(const ShadeRec& sr, const Vector3D& wo, Vector3D& wr) const override;
+
+private:
+
+    float eta_in = 1.0f;
+    float eta_out = 1.0f;
+
+    float fresnel(const ShadeRec& sr) const;
+};
+
+inline void FresnelReflector::set_eta_in(const float eta) { eta_in = eta; }
+
+inline void FresnelReflector::set_eta_out(const float eta) { eta_out = eta; }
+
+#endif

src/BTDFs/BTDF.h

@@ -33,7 +33,7 @@ class BTDF {
 
     BTDF& operator=(BTDF&& btdf) = default;
 
-    virtual BTDF* clone() = 0;
+    virtual BTDF* clone() const = 0;
 
     virtual RGBColor f(const ShadeRec& sr, const Vector3D& wo, const Vector3D& wi) const;
 

src/BTDFs/FresnelTransmitter.cpp

@@ -0,0 +1,81 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#include "FresnelTransmitter.h"
+
+#include <utility>
+#include <cmath>
+
+#include "../Utilities/Vector3D.h"
+#include "../Utilities/ShadeRec.h"
+
+FresnelTransmitter::FresnelTransmitter(const FresnelTransmitter& pt) : BTDF(pt), kt(pt.kt), ior(pt.ior) {}
+
+FresnelTransmitter::FresnelTransmitter(FresnelTransmitter&& pt) noexcept : BTDF(std::move(pt)), kt(std::exchange(pt.kt, 0.0f)), ior(std::exchange(pt.ior, 1.0f)) {}
+
+FresnelTransmitter& FresnelTransmitter::operator=(const FresnelTransmitter& pt) {
+    FresnelTransmitter::operator=(pt);
+    kt = pt.kt;
+    ior = pt.ior;
+
+    return *this;
+}
+
+FresnelTransmitter& FresnelTransmitter::operator=(FresnelTransmitter&& pt) noexcept {
+    FresnelTransmitter::operator=(pt);
+    kt = std::exchange(pt.kt, 0.0f);
+    ior = std::exchange(pt.ior, 1.0f);
+
+    return *this;
+}
+
+FresnelTransmitter* FresnelTransmitter::clone() const { return new FresnelTransmitter(*this); }
+
+// tests for total internal reflection
+
+bool FresnelTransmitter::tir(const ShadeRec& sr) const {
+    Vector3D wo(-sr.ray.d);
+    float cos_thetai = sr.normal * wo;
+    float eta = ior;
+
+    if (cos_thetai < 0.0f) {
+        eta = 1.0f / eta;
+    }
+
+    return 1.0f - (1.0f - cos_thetai * cos_thetai) / (eta * eta) < 0.0f;
+}
+
+RGBColor FresnelTransmitter::f(const ShadeRec& sr, const Vector3D& wo, const Vector3D& wi) const { return RGBColor::black; }
+
+// this computes the direction wt for perfect transmission
+// and returns the transmission coefficient
+// this is only called when there is no total internal reflection
+
+RGBColor FresnelTransmitter::sample_f(const ShadeRec& sr, const Vector3D& wo, Vector3D& wt) const {
+    Normal n(sr.normal);
+    float cos_thetai = n * wo;
+    float eta = ior;
+
+    if (cos_thetai < 0.0f) {  // transmitted ray is outside
+        cos_thetai = -cos_thetai;
+        n = -n;            // reverse direction of normal
+        eta = 1.0f / eta;  // invert ior
+    }
+
+    float temp = 1.0f - (1.0f - cos_thetai * cos_thetai) / (eta * eta);
+    float cos_theta2 = sqrt(temp);
+    wt = -wo / eta - (cos_theta2 - cos_thetai / eta) * n;
+
+    return kt / (eta * eta) * RGBColor::white / fabs(sr.normal * wt);
+}
+
+RGBColor FresnelTransmitter::rho(const ShadeRec& sr, const Vector3D& wo) const { return RGBColor::black; }

src/BTDFs/FresnelTransmitter.h

@@ -0,0 +1,59 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#ifndef __FRESNEL_TRANSMITTER__
+#define __FRESNEL_TRANSMITTER__
+
+#include "BTDF.h"
+
+class FresnelTransmitter : public BTDF {
+public:
+
+    FresnelTransmitter() = default;
+
+    ~FresnelTransmitter() = default;
+
+    FresnelTransmitter(const FresnelTransmitter& pt);
+
+    FresnelTransmitter(FresnelTransmitter&& pt) noexcept;
+
+    FresnelTransmitter& operator=(const FresnelTransmitter& rhs);
+
+    FresnelTransmitter& operator=(FresnelTransmitter&& rhs) noexcept;
+
+    FresnelTransmitter* clone() const override;
+
+    void set_eta_in(const float eta);
+
+    void set_eta_out(const float eta);
+
+    bool tir(const ShadeRec& sr) const;
+
+    RGBColor f(const ShadeRec& sr, const Vector3D& wo, const Vector3D& wi) const override;
+
+    RGBColor sample_f(const ShadeRec& sr, const Vector3D& wo, Vector3D& wt) const override;
+
+    RGBColor rho(const ShadeRec& sr, const Vector3D& wo) const override;
+
+private:
+
+    float eta_in = 1.0f;
+    float eta_out = 1.0f;
+    float kt = 0.0f; // TODO: what is kt?
+    float ior = 0.0f; // TODO: what is ior?
+};
+
+inline void FresnelTransmitter::set_eta_in(const float eta) { eta_in = eta; }
+
+inline void FresnelTransmitter::set_eta_out(const float eta) { eta_out = eta; }
+
+#endif

src/BTDFs/PerfectTransmitter.cpp

@@ -38,7 +38,7 @@ PerfectTransmitter& PerfectTransmitter::operator=(PerfectTransmitter&& pt) noexc
     return *this;
 }
 
-PerfectTransmitter* PerfectTransmitter::clone() { return new PerfectTransmitter(*this); }
+PerfectTransmitter* PerfectTransmitter::clone() const { return new PerfectTransmitter(*this); }
 
 // tests for total internal reflection
 

src/BTDFs/PerfectTransmitter.h

@@ -30,7 +30,7 @@ class PerfectTransmitter : public BTDF {
 
     PerfectTransmitter& operator=(PerfectTransmitter&& rhs) noexcept;
 
-    PerfectTransmitter* clone() override;
+    PerfectTransmitter* clone() const override;
 
     void set_kt(const float k);
 

src/Materials/Dielectric.cpp

@@ -0,0 +1,13 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#include "Dielectric.h"

src/Materials/Dielectric.h

@@ -0,0 +1,22 @@
+//  Copyright (C) Kevin Suffern 2000-2007.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+//  Copyright notice for changes since the originally published version:
+//  Copyright (C) Eduárd Mándy 2019-2021
+//  Though this C++ code was change in a large measure it still has the original copyright notice.
+//  This C++ code is for non-commercial purposes only.
+//  This C++ code is licensed under the GNU General Public License Version 2.
+//  See the file COPYING.txt for the full license.
+
+#ifndef __DIELECTRIC__
+#define __DIELECTRIC__
+
+class Dielectric {
+
+// TODO: implement, 28.3 Implementation, page 601
+
+};
+
+#endif