From 03c825bd3ae2c4d8407e88c1805351512e262cb8 Mon Sep 17 00:00:00 2001
From: NADAL Jean-Baptiste <jbnadal@cabassegroup.com>
Date: Thu, 14 Mar 2024 17:32:14 +0100
Subject: [PATCH] [FEAT] Add a test for Cube

---
 raytracing/src/shapes/cube.cpp | 40 ++++++++++++++++++++++++++++
 raytracing/src/shapes/cube.h   |  3 +++
 tests/12_cubes.cpp             | 48 ++++++++++++++++++++++++++--------
 3 files changed, 80 insertions(+), 11 deletions(-)

diff --git a/raytracing/src/shapes/cube.cpp b/raytracing/src/shapes/cube.cpp
index 02ff638..35dd931 100644
--- a/raytracing/src/shapes/cube.cpp
+++ b/raytracing/src/shapes/cube.cpp
@@ -41,8 +41,19 @@ using namespace Raytracer;
 
 Intersections Cube::local_intersect(const Ray &a_ray)
 {
+    double the_tmin, the_max;
     Intersections the_intersections;
 
+    const auto [the_xtmin, the_xtmax] = check_axis(a_ray.origin().x(), a_ray.direction().x());
+    const auto [the_ytmin, the_ytmax] = check_axis(a_ray.origin().y(), a_ray.direction().y());
+    const auto [the_ztmin, the_ztmax] = check_axis(a_ray.origin().z(), a_ray.direction().z());
+
+    the_tmin = std::max({the_xtmin, the_ytmin, the_ztmin});
+    the_max = std::min({the_xtmax, the_ytmax, the_ztmax});
+
+    the_intersections.add(Intersection(the_tmin, this));
+    the_intersections.add(Intersection(the_max, this));
+
     return the_intersections;
 }
 
@@ -52,3 +63,32 @@ Tuple Cube::local_normal_at(const Tuple &a_local_point) const
 {
     return Tuple::Vector(0, 1, 0);
 }
+
+/* ------------------------------------------------------------------------- */
+
+std::pair<double, double> Cube::check_axis(double an_origin, double a_direction) const
+{
+    double the_tmin, the_tmax;
+    double the_tmin_numerator, the_tmax_numerator;
+
+    the_tmin_numerator = (-1 - an_origin);
+    the_tmax_numerator = (1 - an_origin);
+
+    if (std::abs(a_direction) >= kEpsilon)
+    {
+        the_tmin = the_tmin_numerator / a_direction;
+        the_tmax = the_tmax_numerator / a_direction;
+    }
+    else
+    {
+        the_tmin = the_tmin_numerator * std::numeric_limits<double>::infinity();
+        the_tmax = the_tmax_numerator * std::numeric_limits<double>::infinity();
+    }
+
+    if (the_tmin > the_tmax)
+    {
+        std::swap(the_tmin, the_tmax);
+    }
+
+    return {the_tmin, the_tmax};
+}
diff --git a/raytracing/src/shapes/cube.h b/raytracing/src/shapes/cube.h
index 74d7d84..66fd472 100644
--- a/raytracing/src/shapes/cube.h
+++ b/raytracing/src/shapes/cube.h
@@ -40,6 +40,9 @@ namespace Raytracer
         Cube(void) = default;
         Intersections local_intersect(const Ray &a_ray) override;
         Tuple local_normal_at(const Tuple &a_local_point) const override;
+
+    private:
+        std::pair<double, double> check_axis(double an_origin, double a_direction) const;
     };
 }; // namespace Raytracer
 
diff --git a/tests/12_cubes.cpp b/tests/12_cubes.cpp
index ddbd9f0..2ad1c02 100644
--- a/tests/12_cubes.cpp
+++ b/tests/12_cubes.cpp
@@ -33,7 +33,18 @@ using namespace Raytracer;
 
 /* ------------------------------------------------------------------------- */
 
-SCENARIO("Reflectivity for the default material", "[features/cubes.feature]")
+class CubeTest
+{
+public:
+    Tuple origin;
+    Tuple direction;
+    double t1;
+    double t2;
+};
+
+/* ------------------------------------------------------------------------- */
+
+SCENARIO("A Ray intersects a cube", "[features/cubes.feature]")
 {
     // |        | origin            | direction        | t1 | t2 |
     // | +x     | point(5, 0.5, 0)  | vector(-1, 0, 0) | 4  | 6  |
@@ -43,6 +54,16 @@ SCENARIO("Reflectivity for the default material", "[features/cubes.feature]")
     // | +z     | point(0.5, 0, 5)  | vector( 0, 0,-1) | 4  | 6  |
     // | -z     | point(0.5, 0, -5) | vector( 0, 0, 1) | 4  | 6  |
     // | inside | point(0, 0.5, 0)  | vector( 0, 0, 1) | -1 | -1 |
+    CubeTest the_test[7] = {
+        { Tuple::Point(5.0,  0.5,  0.0), Tuple::Vector(-1,  0,  0),  4,  6},
+        {Tuple::Point(-5.0,  0.5,  0.0),  Tuple::Vector(1,  0,  0),  4,  6},
+        { Tuple::Point(0.5,  5.0,  0.0),  Tuple::Vector(0, -1,  0),  4,  6},
+        { Tuple::Point(0.5, -5.0,  0.0),  Tuple::Vector(0,  1,  0),  4,  6},
+        { Tuple::Point(0.5,  0.0,  5.0),  Tuple::Vector(0,  0, -1),  4,  6},
+        { Tuple::Point(0.5,  0.0, -5.0),  Tuple::Vector(0,  0,  1),  4,  6},
+        { Tuple::Point(0.0,  0.5,  0.0),  Tuple::Vector(0,  0,  1), -1, -1}
+    };
+
     GIVEN("c <- cube()")
     {
         Cube c;
@@ -50,17 +71,22 @@ SCENARIO("Reflectivity for the default material", "[features/cubes.feature]")
         {
             WHEN("xs <- local_intersect(c,r)")
             {
-                THEN("xs.count = 2")
+                for (int i = 0; i < 7; i++)
                 {
-                    // REQUIRE();
-                }
-                AND_THEN("xs[0].t = <t1>")
-                {
-                    // REQUIRE();
-                }
-                AND_THEN("xs[1].t = <t2>")
-                {
-                    // REQUIRE();
+                    Ray r(the_test[i].origin, the_test[i].direction);
+                    Intersections xs = c.local_intersect(r);
+                    THEN("xs.count = 2")
+                    {
+                        REQUIRE(xs.count() == 2);
+                    }
+                    AND_THEN("xs[0].t = <t1>")
+                    {
+                        REQUIRE(xs[0].distance_t() == the_test[i].t1);
+                    }
+                    AND_THEN("xs[1].t = <t2>")
+                    {
+                        REQUIRE(xs[1].distance_t() == the_test[i].t2);
+                    }
                 }
             }
         }