From b26a0168788a28c384d394b9e3bb4ebaebc815c2 Mon Sep 17 00:00:00 2001
From: Keuin <keuinx@gmail.com>
Date: Sat, 16 Apr 2022 14:31:38 +0800
Subject: Add dielectric material. (glass ball)

---
 CMakeLists.txt          |  4 ++--
 main_simple_scanner.cpp | 16 +++++++++++++++-
 material_dielectric.cpp | 22 ++++++++++++++++++++++
 material_dielectric.h   | 18 ++++++++++++++++++
 4 files changed, 57 insertions(+), 3 deletions(-)
 create mode 100644 material_dielectric.cpp
 create mode 100644 material_dielectric.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2ed3de8..a197031 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,9 +12,9 @@ set(CMAKE_VERBOSE_MAKEFILE on)
 
 # main executable
 
-add_executable(rt main.cpp vec.h bitmap.h ray.h bitfont.h hitlist.h object.h sphere.h viewport.h aa.h material.h material_diffusive.h material_diffusive.cpp material_reflective.h material_reflective.cpp)
+add_executable(rt main.cpp vec.h bitmap.h ray.h bitfont.h hitlist.h object.h sphere.h viewport.h aa.h material.h material_diffusive.h material_diffusive.cpp material_reflective.h material_reflective.cpp material_dielectric.cpp material_dielectric.h)
 add_executable(image_output main_image_output.cpp vec.h bitmap.h bitfont.h hitlist.h object.h sphere.h viewport.h)
-add_executable(simple_scanner main_simple_scanner.cpp vec.h bitmap.h ray.h timer.h bitfont.h hitlist.h object.h sphere.h viewport.h aa.h material.h material_diffusive.h material_diffusive.cpp material_reflective.h material_reflective.cpp)
+add_executable(simple_scanner main_simple_scanner.cpp vec.h bitmap.h ray.h timer.h bitfont.h hitlist.h object.h sphere.h viewport.h aa.h material.h material_diffusive.h material_diffusive.cpp material_reflective.h material_reflective.cpp material_dielectric.cpp material_dielectric.h)
 
 # googletest
 
diff --git a/main_simple_scanner.cpp b/main_simple_scanner.cpp
index b116933..6e79293 100644
--- a/main_simple_scanner.cpp
+++ b/main_simple_scanner.cpp
@@ -16,10 +16,12 @@
 #include "aa.h"
 #include "material_diffusive.h"
 #include "material_reflective.h"
+#include "material_dielectric.h"
 
 // Select the scene to render
 //#define SCENE_DIFFUSE
-#define SCENE_REFLECT
+//#define SCENE_REFLECT
+#define SCENE_DIALECT
 
 // T: intermediate color depth
 template<typename T>
@@ -58,6 +60,18 @@ void generate_image(uint16_t image_width, uint16_t image_height, double viewport
     world.add_object(std::make_shared<sphere>(vec3d{-1.0, 0.0, -1.0}, 0.5, m_ball_left));
     world.add_object(std::make_shared<sphere>(vec3d{0.0, 0.0, -1.0}, 0.5, m_ball_center));
     world.add_object(std::make_shared<sphere>(vec3d{1.0, 0.0, -1.0}, 0.5, m_ball_right));
+#endif
+#ifdef SCENE_DIALECT
+    material_diffuse_lambertian m_ground{{0.8, 0.8, 0.0}};
+    material_diffuse_lambertian m_ball_center{{0.7, 0.3, 0.3}};
+    material_dielectric m_ball_left{1.5};
+    material_reflective m_ball_right{{0.8, 0.6, 0.2}};
+    // the earth
+    world.add_object(std::make_shared<sphere>(vec3d{0.0, -100.5, -1.0}, 100.0, m_ground));
+    // three balls
+    world.add_object(std::make_shared<sphere>(vec3d{-1.0, 0.0, -1.0}, 0.5, m_ball_left));
+    world.add_object(std::make_shared<sphere>(vec3d{0.0, 0.0, -1.0}, 0.5, m_ball_center));
+    world.add_object(std::make_shared<sphere>(vec3d{1.0, 0.0, -1.0}, 0.5, m_ball_right));
 #endif
     timer tm;
     std::cerr << "Rendering..." << std::endl;
diff --git a/material_dielectric.cpp b/material_dielectric.cpp
new file mode 100644
index 0000000..3aaf259
--- /dev/null
+++ b/material_dielectric.cpp
@@ -0,0 +1,22 @@
+//
+// Created by Keuin on 2022/4/15.
+//
+
+#include "material_dielectric.h"
+
+bool material_dielectric::scatter(ray3d &r, const object &hit_obj, double hit_t, random_uv_gen_3d &ruvg) const {
+    const auto hit_p = r.at(hit_t);
+    assert(hit_obj.is_on(hit_p));
+    auto n = hit_obj.normal_vector(hit_p);
+    auto ri_ = ri_inv;
+    if (dot(r.direction(), n) > 0) {
+        // the ray is started from the object's inner,
+        // use normal vector and ri on the surface's inner side
+        n = -n;
+        ri_ = 1.0 / ri_;
+    }
+    const auto r2 = n.refract<true>(r.direction(), ri_); // refracted vector
+    r.direction(r2.unit_vec());
+    r.source(hit_p);
+    return true;
+}
diff --git a/material_dielectric.h b/material_dielectric.h
new file mode 100644
index 0000000..48382b4
--- /dev/null
+++ b/material_dielectric.h
@@ -0,0 +1,18 @@
+//
+// Created by Keuin on 2022/4/15.
+//
+
+#ifndef RT_MATERIAL_DIELECTRIC_H
+#define RT_MATERIAL_DIELECTRIC_H
+
+#include "vec.h"
+#include "material.h"
+
+class material_dielectric : public material {
+    double ri_inv;
+public:
+    explicit material_dielectric(double ri) : ri_inv{1.0 / ri} {}
+    bool scatter(ray3d &r, const object &hit_obj, double hit_t, random_uv_gen_3d &ruvg) const override;
+};
+
+#endif //RT_MATERIAL_DIELECTRIC_H
-- 
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