[FEAT] Add Plane Chapter 09 is done

README.md

@@ -23,6 +23,6 @@ The Web Site of the book: http://raytracerchallenge.com/
 | :------------------------: | :------------------------: |
 | ![05](data/chapter_05.png) | ![06](data/chapter_06.png) |
 
-| Chapiter 07                |  Chapiter 08                   |
+| Chapiter 07               | Chapiter 08                |  Chapiter 09                   |
-| :------------------------: | :----------------------------: |
+|:------------------------: | :------------------------: | :----------------------------: |
-| ![07](data/chapter_07.png) | ![08](data/chapter_08.png)     |
+|![07](data/chapter_07.png) | ![08](data/chapter_08.png) | ![09](data/chapter_09.png)     |

apps/CMakeLists.txt

@@ -13,3 +13,6 @@ target_link_libraries(chapter_06 PRIVATE raytracing gcov)
 
 add_executable(chapter_07 chapter_07.cpp)
 target_link_libraries(chapter_07 PRIVATE raytracing gcov)
+
+add_executable(chapter_09 chapter_09.cpp)
+target_link_libraries(chapter_09 PRIVATE raytracing gcov)

apps/chapter_09.cpp

@@ -0,0 +1,101 @@
+/*!
+ * chapter_09.cpp
+ *
+ * Copyright (c) 2024, NADAL Jean-Baptiste. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ *
+ * @Author:  NADAL Jean-Baptiste
+ * @Date: 26/02/2024
+ *
+ */
+
+// This is an independent project of an individual developer. Dear PVS-Studio, please check it.
+// PVS-Studio Static Code Analyzer for C, C++, C#, and Java: http://www.viva64.com
+
+#include <chrono>
+#include <cstdio>
+
+#include <raytracing.h>
+
+/* ------------------------------------------------------------------------- */
+
+using namespace Raytracer;
+using namespace std;
+
+/* ------------------------------------------------------------------------- */
+
+int main(void)
+{
+    World the_world;
+    Camera the_camera;
+    Canvas the_canvas;
+    Plane *the_floor;
+    Sphere *the_middle, *the_right, *the_left;
+    chrono::time_point<chrono::high_resolution_clock> the_start, the_end;
+
+    printf("Chapter 09 example.\n");
+
+    // Floor is an extremely flattened sphere with a matte texture.
+    the_floor = new Plane();
+    the_floor->material().set_color(Color(1, 0.9, 0.9));
+    the_floor->material().set_specular(0);
+    the_world.add_object(the_floor);
+
+    // The large sphere in the middle is a unit sphere, translated upward slightly and colored green.
+    the_middle = new Sphere();
+    the_middle->set_transform(Matrix::translation(-0.5, 1, 0.5));
+    the_middle->material().set_color(Color(0.1, 1, 0.5));
+    the_middle->material().set_diffuse(0.7);
+    the_middle->material().set_specular(0.3);
+    the_world.add_object(the_middle);
+
+    // The smaller green sphere on the right is scaled in half
+    the_right = new Sphere();
+    the_right->set_transform(Matrix::translation(1.5, 0.5, -0.5) * Matrix::scaling(0.5, 0.5, 0.5));
+    the_right->material().set_color(Color(0.5, 1, 0.1));
+    the_right->material().set_diffuse(0.7);
+    the_right->material().set_specular(0.3);
+    the_world.add_object(the_right);
+
+    // The smallest sphere is scaled by a third, before being translated
+    the_left = new Sphere();
+    the_left->set_transform(Matrix::translation(-1.5, 0.33, -0.75) * Matrix::scaling(0.33, 0.33, 0.33));
+    the_left->material().set_color(Color(1, 0.8, 0.1));
+    the_left->material().set_diffuse(0.7);
+    the_left->material().set_specular(0.3);
+    the_world.add_object(the_left);
+
+    // The Light source is white, shining from above and to the left
+    the_world.set_light(PointLight(Tuple::Point(-10, 10, -10), Color(1, 1, 1)));
+
+    // Configure the camera.
+    // the_camera = Camera(100, 50, std::numbers::pi / 2);
+    the_camera = Camera(320, 200, std::numbers::pi / 2);
+    the_camera.set_transform(
+        Matrix::view_transform(Tuple::Point(0, 1.5, -3.5), Tuple::Point(0, 1, 0), Tuple::Vector(0, 1, 0)));
+
+    the_start  = chrono::high_resolution_clock::now();
+    the_canvas = the_camera.render(the_world);
+    the_end    = chrono::high_resolution_clock::now();
+
+    the_canvas.save_to_file("chapter09.ppm");
+
+    chrono::duration<double> the_elapsed_time = the_end - the_start;
+    printf("Execution Time: %f secondes\n", the_elapsed_time.count());
+
+    return 0;
+}

raytracing/CMakeLists.txt

@@ -24,6 +24,7 @@ add_library(raytracing
     src/renderer/material.cpp
     src/renderer/ray.cpp
     src/renderer/world.cpp
+    src/shapes/plane.cpp
     src/shapes/shape.cpp
     src/shapes/sphere.cpp
 )

raytracing/include/raytracing.h

@@ -38,4 +38,5 @@
 #include "renderer/material.h"
 #include "renderer/ray.h"
 #include "renderer/world.h"
-#include "shapes/sphere.h"
+#include "shapes/plane.h"
+#include "shapes/sphere.h"

raytracing/src/core/intersection-data.cpp

@@ -34,7 +34,7 @@ using namespace Raytracer;
 
 /* ------------------------------------------------------------------------- */
 
-IntersectionData::IntersectionData(void) : m_is_inside(false), m_distance(0)
+IntersectionData::IntersectionData(void) : m_is_inside(false), m_distance(0), m_shape(nullptr)
 {
 }
 
@@ -56,12 +56,12 @@ void IntersectionData::set_distance_t(double a_value)
 
 const Shape &IntersectionData::object(void) const
 {
-    return m_shape;
+    return *m_shape;
 }
 
 /* ------------------------------------------------------------------------- */
 
-void IntersectionData::set_object(const Shape &a_shape)
+void IntersectionData::set_object(Shape *a_shape)
 {
     m_shape = a_shape;
 }

raytracing/src/core/intersection-data.h

@@ -45,7 +45,7 @@ namespace Raytracer
         void set_distance_t(double a_value);
 
         const Shape &object(void) const;
-        void set_object(const Shape &a_shape);
+        void set_object(Shape *a_shape);
 
         const Tuple &point(void) const;
         void set_point(const Tuple &a_point);
@@ -65,7 +65,7 @@ namespace Raytracer
     private:
         bool m_is_inside;
         double m_distance;
-        Shape m_shape; // TODO ??
+        Shape *m_shape;
         Tuple m_point;
         Tuple m_over_point;
         Tuple m_eyev;

raytracing/src/core/intersection.cpp

@@ -36,13 +36,13 @@ using namespace Raytracer;
 
 /* ------------------------------------------------------------------------- */
 
-Intersection::Intersection(void) : m_is_nothing(true), m_distance_t(0.0), m_shape()
+Intersection::Intersection(void) : m_is_nothing(true), m_distance_t(0.0), m_shape(nullptr)
 {
 }
 
 /* ------------------------------------------------------------------------- */
 
-Intersection::Intersection(double a_distance_t, const Shape &a_shape) :
+Intersection::Intersection(double a_distance_t, Shape *a_shape) :
     m_is_nothing(false),
     m_distance_t(a_distance_t),
     m_shape(a_shape)
@@ -143,7 +143,7 @@ double Intersection::distance_t(void) const
 
 const Shape &Intersection::object(void) const
 {
-    return m_shape;
+    return *m_shape;
 }
 
 /* ------------------------------------------------------------------------- */
@@ -173,7 +173,7 @@ IntersectionData Intersection::prepare_computations(Ray a_ray) const
     // Precompute some useful values
     the_data.set_point(a_ray.position(m_distance_t));
     the_data.set_eyev(-a_ray.direction());
-    the_data.set_normalv(m_shape.normal_at(the_data.point()));
+    the_data.set_normalv(m_shape->normal_at(the_data.point()));
     the_data.set_over_point(the_data.point() + the_data.normalv() * kEpsilon);
     the_data.set_inside();
 

raytracing/src/core/intersection.h

@@ -41,7 +41,7 @@ namespace Raytracer
     {
     public:
         Intersection(void);
-        Intersection(double a_distance_t, const Shape &a_shape);
+        Intersection(double a_distance_t, Shape *a_shape);
         Intersection(Intersection &an_intersection);
         Intersection(const Intersection &an_intersection);
 
@@ -65,7 +65,7 @@ namespace Raytracer
     private:
         bool m_is_nothing;
         double m_distance_t;
-        Shape m_shape;
+        Shape *m_shape;
     };
 }; // namespace Raytracer
 

raytracing/src/shapes/plane.cpp

@@ -0,0 +1,63 @@
+/*!
+ * sphere.cpp
+ *
+ * Copyright (c) 2024, NADAL Jean-Baptiste. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ *
+ * @Author:  NADAL Jean-Baptiste
+ * @Date: 05/02/2024
+ *
+ */
+
+// This is an independent project of an individual developer. Dear PVS-Studio, please check it.
+// PVS-Studio Static Code Analyzer for C, C++, C#, and Java: http://www.viva64.com
+
+/* ------------------------------------------------------------------------- */
+
+#include <cmath>
+
+#include "core/common.h"
+#include "core/intersections.h"
+
+#include "plane.h"
+
+using namespace Raytracer;
+
+/* ------------------------------------------------------------------------- */
+
+Intersections Plane::local_intersect(const Ray &a_ray)
+{
+    Intersections the_intersections;
+
+    if (std::abs(a_ray.direction().y()) < kEpsilon)
+    {
+        return the_intersections;
+    }
+
+    double the_t = -a_ray.origin().y() / a_ray.direction().y();
+
+    the_intersections.add(Intersection(the_t, this));
+
+    return the_intersections;
+}
+
+/* ------------------------------------------------------------------------- */
+
+Tuple Plane::local_normal_at(const Tuple &a_local_point) const
+{
+    return Tuple::Vector(0, 1, 0);
+}

raytracing/src/shapes/plane.h

@@ -0,0 +1,46 @@
+/*!
+ * plane.h
+ *
+ * Copyright (c) 2024, NADAL Jean-Baptiste. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ *
+ * @Author:  NADAL Jean-Baptiste
+ * @Date: 27/02/2024
+ *
+ */
+
+#ifndef _RAYTRACER_PLANE_H
+#define _RAYTRACER_PLANE_H
+
+/* ------------------------------------------------------------------------- */
+
+#include "shapes/shape.h"
+
+/* ------------------------------------------------------------------------- */
+
+namespace Raytracer
+{
+    class Plane : public Shape
+    {
+    public:
+        Plane(void) = default;
+        Intersections local_intersect(const Ray &a_ray) override;
+        Tuple local_normal_at(const Tuple &a_local_point) const override;
+    };
+}; // namespace Raytracer
+
+#endif // _RAYTRACER_PLANE_H

raytracing/src/shapes/shape.cpp

@@ -38,23 +38,21 @@ using namespace Raytracer;
 
 #define kNothing 0
 
-uint32_t Shape::s_current_index = 0;
-
 /* ------------------------------------------------------------------------- */
 
-Shape::Shape(void) : m_id(kNothing), m_transform(Matrix::identity())
+Shape::Shape(void) : m_transform(Matrix::identity())
 {
 }
 
 /* ------------------------------------------------------------------------- */
 
-Shape::Shape(Shape &a_copy) : m_id(a_copy.m_id), m_transform(a_copy.m_transform), m_material(a_copy.m_material)
+Shape::Shape(Shape &a_copy) : m_transform(a_copy.m_transform), m_material(a_copy.m_material)
 {
 }
 
 /* ------------------------------------------------------------------------- */
 
-Shape::Shape(const Shape &a_copy) : m_id(a_copy.m_id), m_transform(a_copy.m_transform), m_material(a_copy.m_material)
+Shape::Shape(const Shape &a_copy) : m_transform(a_copy.m_transform), m_material(a_copy.m_material)
 {
 }
 
@@ -67,7 +65,6 @@ const Shape &Shape::operator=(const Shape &a_shape)
         return *this;
     }
 
-    m_id        = a_shape.m_id;
     m_transform = a_shape.m_transform;
     m_material  = a_shape.m_material;
 
@@ -78,7 +75,6 @@ const Shape &Shape::operator=(const Shape &a_shape)
 
 bool Shape::operator==(const Shape &a_shape) const
 {
-    // (m_id == a_shape.m_id) && (
     return (m_transform == a_shape.m_transform) && (m_material == a_shape.m_material);
 }
 
@@ -159,10 +155,3 @@ Intersections Shape::local_intersect(const Ray &a_ray)
 
     return the_ret;
 }
-
-/* ------------------------------------------------------------------------- */
-
-void Shape::inc_id(void)
-{
-    m_id = s_current_index++;
-}

raytracing/src/shapes/shape.h

@@ -66,14 +66,9 @@ namespace Raytracer
         Intersections intersect(const Ray &a_ray);
         virtual Intersections local_intersect(const Ray &a_ray);
 
-    protected:
-        void inc_id(void);
-
     private:
-        uint32_t m_id;
         Matrix m_transform;
         Material m_material;
-        static uint32_t s_current_index;
     };
 }; // namespace Raytracer
 

raytracing/src/shapes/sphere.cpp

@@ -39,13 +39,6 @@ using namespace Raytracer;
 
 /* ------------------------------------------------------------------------- */
 
-Sphere::Sphere(void)
-{
-    inc_id();
-}
-
-/* ------------------------------------------------------------------------- */
-
 Intersections Sphere::local_intersect(const Ray &a_ray)
 {
     Intersections the_intersections;
@@ -61,8 +54,8 @@ Intersections Sphere::local_intersect(const Ray &a_ray)
     if (discriminant >= 0)
     {
         double the_sqrt = std::sqrt(discriminant);
-        the_intersections.add(Intersection((-the_b - the_sqrt) / (2 * the_a), *this));
+        the_intersections.add(Intersection((-the_b - the_sqrt) / (2 * the_a), this));
-        the_intersections.add(Intersection((-the_b + the_sqrt) / (2 * the_a), *this));
+        the_intersections.add(Intersection((-the_b + the_sqrt) / (2 * the_a), this));
     }
 
     return the_intersections;

raytracing/src/shapes/sphere.h

@@ -37,7 +37,7 @@ namespace Raytracer
     class Sphere : public Shape
     {
     public:
-        Sphere(void);
+        Sphere(void) = default;
         Intersections local_intersect(const Ray &a_ray) override;
         Tuple local_normal_at(const Tuple &a_local_point) const override;
     };

tests/05_rays.cpp

@@ -234,7 +234,7 @@ SCENARIO("An intersection encapsulates t and object", "[features/intersections.f
         Sphere s;
         WHEN("intersection(3.5,s)")
         {
-            Intersection i(3.5, s);
+            Intersection i(3.5, &s);
 
             THEN("i.t = 3.5")
             {
@@ -257,7 +257,7 @@ SCENARIO("An intersection could be affected", "[features/intersections.feature]"
         Sphere s;
         AND_GIVEN("i1 <- intersection(3.5,s) and i2 <- intersection()")
         {
-            Intersection i1(3.5, s);
+            Intersection i1(3.5, &s);
             Intersection i2;
 
             WHEN("i2 <- i1")
@@ -286,8 +286,8 @@ SCENARIO("Intersection could be compared", "[features/intersections.feature]")
         Sphere s;
         AND_GIVEN("i1 <- intersection(3,s) and i2 <- intersection(4,s)")
         {
-            Intersection i1(3.0, s);
+            Intersection i1(3.0, &s);
-            Intersection i2(4.0, s);
+            Intersection i2(4.0, &s);
 
             THEN("i2 > i1")
             {
@@ -326,10 +326,10 @@ SCENARIO("Aggregating intersections", "[features/intersections.feature]")
         Sphere s;
         AND_GIVEN("i1 <- intersection(1,s)")
         {
-            Intersection i1(1, s);
+            Intersection i1(1, &s);
             AND_GIVEN("i2 <- intersection(2,s)")
             {
-                Intersection i2(2, s);
+                Intersection i2(2, &s);
                 WHEN("xs <- intersections(i1,i2)")
                 {
                     Intersections xs = Intersections({i1, i2});
@@ -361,7 +361,7 @@ SCENARIO("Operations with intersections", "[features/intersections.feature]")
         AND_GIVEN("s <- sphere()")
         {
             Sphere s;
-            Intersection i1(1, s);
+            Intersection i1(1, &s);
             AND_GIVEN("xs2 <- intersections({i1})")
             {
                 Intersections xs2({i1});
@@ -423,10 +423,10 @@ SCENARIO("The hit, when all intersections have positive t", "[features/intersect
         Sphere s;
         AND_GIVEN("i1 <- intersection(1,s)")
         {
-            Intersection i1(1, s);
+            Intersection i1(1, &s);
             AND_GIVEN("i2 <- intersection(2,s)")
             {
-                Intersection i2(2, s);
+                Intersection i2(2, &s);
                 AND_GIVEN("xs <- intersections(i1,i2)")
                 {
                     Intersections xs = Intersections({i2, i1});
@@ -453,10 +453,10 @@ SCENARIO("The hit, when some intersections have negative t", "[features/intersec
         Sphere s;
         AND_GIVEN("i1 <- intersection(-1,s)")
         {
-            Intersection i1(-1, s);
+            Intersection i1(-1, &s);
             AND_GIVEN("i2 <- intersection(2,s)")
             {
-                Intersection i2(1, s);
+                Intersection i2(1, &s);
                 AND_GIVEN("xs <- intersections(i1,i2)")
                 {
                     Intersections xs = Intersections({i2, i1});
@@ -483,10 +483,10 @@ SCENARIO("The hit, when all intersections have negative t", "[features/intersect
         Sphere s;
         AND_GIVEN("i1 <- intersection(-2,s)")
         {
-            Intersection i1(-2, s);
+            Intersection i1(-2, &s);
             AND_GIVEN("i2 <- intersection(-1,s)")
             {
-                Intersection i2(-1, s);
+                Intersection i2(-1, &s);
                 AND_GIVEN("xs <- intersections(i1,i2)")
                 {
                     Intersections xs = Intersections({i1, i2});
@@ -514,16 +514,16 @@ SCENARIO("The hit is always the lowest nonnegative intersection", "[features/int
         Sphere s;
         AND_GIVEN("i1 <- intersection(5,s)")
         {
-            Intersection i1(5, s);
+            Intersection i1(5, &s);
             AND_GIVEN("i2 <- intersection(7,s)")
             {
-                Intersection i2(7, s);
+                Intersection i2(7, &s);
                 AND_GIVEN("i3 <- intersection(-3,s)")
                 {
-                    Intersection i3(-3, s);
+                    Intersection i3(-3, &s);
                     AND_GIVEN("i4 <- intersection(2,s)")
                     {
-                        Intersection i4(2, s);
+                        Intersection i4(2, &s);
                         AND_GIVEN("xs <- intersections(i1, i2, i3, i4)")
                         {
                             Intersections xs = Intersections({i1, i2, i3, i4});

tests/07_making_scene.cpp

@@ -143,7 +143,7 @@ SCENARIO("Precompute the state of an intersection", "[features/intersections.fea
             Sphere shape;
             AND_GIVEN("i <- intersection(4, shape)")
             {
-                Intersection i(4, shape);
+                Intersection i(4, &shape);
                 WHEN("comps <- prepare_computations(i,r)")
                 {
                     IntersectionData comps = i.prepare_computations(r);
@@ -185,7 +185,7 @@ SCENARIO("The hit, when an intersection occurs on the outside", "[features/inter
             Sphere shape;
             AND_GIVEN("i <- intersection(4, shape)")
             {
-                Intersection i(4, shape);
+                Intersection i(4, &shape);
                 WHEN("comps <- prepare_computations(i,r)")
                 {
                     IntersectionData comps = i.prepare_computations(r);
@@ -211,7 +211,7 @@ SCENARIO("The hit, when an intersection occurs on the inside", "[features/inters
             Sphere shape;
             AND_GIVEN("i <- intersection(1, shape)")
             {
-                Intersection i(1, shape);
+                Intersection i(1, &shape);
                 WHEN("comps <- prepare_computations(i,r)")
                 {
                     IntersectionData comps = i.prepare_computations(r);
@@ -252,7 +252,7 @@ SCENARIO("Shading an intersection", "[features/world.feature]")
                 Shape *shape = w.objects(0);
                 AND_GIVEN("i <- intersection(4, shape)")
                 {
-                    Intersection i(4, *shape);
+                    Intersection i(4, shape);
                     WHEN("comps <- prepare_computations(i,r)")
                     {
                         IntersectionData comps = i.prepare_computations(r);
@@ -289,7 +289,7 @@ SCENARIO("Shading an intersection from the inside", "[features/world.feature]")
                     Shape *shape = w.objects(1);
                     AND_GIVEN("i <- intersection(0.5, shape)")
                     {
-                        Intersection i(0.5, *shape);
+                        Intersection i(0.5, shape);
                         WHEN("comps <- prepare_computations(i,r)")
                         {
                             IntersectionData comps = i.prepare_computations(r);

tests/08_shadows.cpp

@@ -164,7 +164,7 @@ SCENARIO("shade_hit() is given an intersection in the shadow", "[features/world.
                                 Ray r(Tuple::Point(0, 0, 5), Tuple::Vector(0, 0, 1));
                                 AND_GIVEN("i <- intersection(4, s2)")
                                 {
-                                    Intersection i(4, *s2);
+                                    Intersection i(4, s2);
                                     WHEN("comps <- prepare_computatons(i,r)")
                                     {
                                         IntersectionData comps = i.prepare_computations(r);
@@ -200,7 +200,7 @@ SCENARIO("The hit should offset the point", "[features/intersections.feature]")
             shape.set_transform(Matrix::translation(0, 0, 1));
             AND_GIVEN("i <- intersection(5, shape)")
             {
-                Intersection i(5, shape);
+                Intersection i(5, &shape);
                 WHEN("comps <- prepare_computatons(i,r)")
                 {
                     IntersectionData comps = i.prepare_computations(r);

tests/09_planes.cpp

@@ -244,3 +244,142 @@ SCENARIO("Computing the normal on a transformed shape", "[features/shapes.featur
         }
     }
 }
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("The normal of a plane is constant everywhere", "[features/planes.feature]")
+{
+    GIVEN("p <- plane()")
+    {
+        Plane p;
+        WHEN("n1 <- local_normal_at(p, point(0, 0, 0)))")
+        {
+            Tuple n1 = p.local_normal_at(Tuple::Point(0, 0, 0));
+            AND_WHEN("n2 <- local_normal_at(p, point(10, 0, 0)))")
+            {
+                Tuple n2 = p.local_normal_at(Tuple::Point(10, 0, 0));
+                AND_WHEN("n3 <- local_normal_at(p, point(-5, 0, 150)))")
+                {
+                    Tuple n3 = p.local_normal_at(Tuple::Point(-5, 0, 150));
+
+                    THEN("n1 = vector(0, 1, 0)")
+                    {
+                        REQUIRE(n1 == Tuple::Vector(0, 1, 0));
+                    }
+                    AND_THEN("n2 = vector(0, 1, 0)")
+                    {
+                        REQUIRE(n1 == Tuple::Vector(0, 1, 0));
+                    }
+                    AND_THEN("n3 = vector(0, 1, 0)")
+                    {
+                        REQUIRE(n1 == Tuple::Vector(0, 1, 0));
+                    }
+                }
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("Intersect with a ray parallel to the plane", "[features/planes.feature]")
+{
+    GIVEN("p <- plane()")
+    {
+        Plane p;
+        AND_GIVEN("r <- ray(point(0, 10, 0), vector(0, 0, 1))")
+        {
+            Ray r(Tuple::Point(0, 10, 0), Tuple::Vector(0, 0, 1));
+            WHEN("xs <-local_intersect(p, r)")
+            {
+                Intersections xs = p.local_intersect(r);
+                THEN("xs is empty")
+                {
+                    REQUIRE(xs.count() == 0);
+                }
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("Intersect with a coplanar ray", "[features/planes.feature]")
+{
+    GIVEN("p <- plane()")
+    {
+        Plane p;
+        AND_GIVEN("r <- ray(point(0, 0, 0), vector(0, 0, 1))")
+        {
+            Ray r(Tuple::Point(0, 0, 0), Tuple::Vector(0, 0, 1));
+            WHEN("xs <-local_intersect(p, r)")
+            {
+                Intersections xs = p.local_intersect(r);
+                THEN("xs is empty")
+                {
+                    REQUIRE(xs.count() == 0);
+                }
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("A ray Intersecting a plane from above", "[features/planes.feature]")
+{
+    GIVEN("p <- plane()")
+    {
+        Plane p;
+        AND_GIVEN("r <- ray(point(0, 1, 0), vector(0, -1, 0))")
+        {
+            Ray r(Tuple::Point(0, 1, 0), Tuple::Vector(0, -1, 0));
+            WHEN("xs <-local_intersect(p, r)")
+            {
+                Intersections xs = p.local_intersect(r);
+                THEN("xs.count = 1")
+                {
+                    REQUIRE(xs.count() == 1);
+                }
+                AND_THEN("xs[0].t = 1")
+                {
+                    REQUIRE(xs[0].distance_t() == 1);
+                }
+                AND_THEN("xs[0].object = p")
+                {
+                    REQUIRE(xs[0].object() == p);
+                }
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("A ray Intersecting a plane from below", "[features/planes.feature]")
+{
+    GIVEN("p <- plane()")
+    {
+        Plane p;
+        AND_GIVEN("r <- ray(point(0, -1, 0), vector(0, 1, 0))")
+        {
+            Ray r(Tuple::Point(0, -1, 0), Tuple::Vector(0, 1, 0));
+            WHEN("xs <-local_intersect(p, r)")
+            {
+                Intersections xs = p.local_intersect(r);
+                THEN("xs.count = 1")
+                {
+                    REQUIRE(xs.count() == 1);
+                }
+                AND_THEN("xs[0].t = 1")
+                {
+                    REQUIRE(xs[0].distance_t() == 1);
+                }
+                AND_THEN("xs[0].object = p")
+                {
+                    REQUIRE(xs[0].object() == p);
+                }
+            }
+        }
+    }
+}