Smooth triangles! And support for them in the OBJ File parser.

Also add an interesting tea party scene!

tests/smoothtriangle_test.cpp

@@ -0,0 +1,83 @@
+/*
+ *  DoRayMe - a quick and dirty Raytracer
+ *  Smooth Triangle unit tests
+ *
+ *  Created by Manoël Trapier
+ *  Copyright (c) 2020 986-Studio.
+ *
+ */
+#include <smoothtriangle.h>
+#include <math.h>
+#include <gtest/gtest.h>
+
+class SmoothTriTest : public SmoothTriangle
+{
+public:
+    SmoothTriTest(Point p1, Point p2, Point p3, Vector n1, Vector n2, Vector n3) : SmoothTriangle(p1, p2, p3, n1, n2, n3) {};
+    Intersect doLocalIntersect(Ray ray)
+    {
+        return this->localIntersect(ray);
+    };
+
+    Tuple doLocalNormalAt(Tuple point, Intersection *hit)
+    {
+      return this->localNormalAt(point, hit);
+    };
+};
+
+Point p1 = Point(0, 1, 0);
+Point p2 = Point(-1, 0, 0);
+Point p3 = Point(1, 0, 0);
+Vector n1 = Vector(0, 1, 0);
+Vector n2 = Vector(-1, 0, 0);
+Vector n3 = Vector(1, 0, 0);
+
+SmoothTriTest tri = SmoothTriTest(p1, p2, p3, n1, n2, n3);
+
+TEST(SmoothTriangleTest, Construcring_a_smooth_triangle)
+{
+    ASSERT_EQ(tri.p1, p1);
+    ASSERT_EQ(tri.p2, p2);
+    ASSERT_EQ(tri.p3, p3);
+    ASSERT_EQ(tri.n1, n1);
+    ASSERT_EQ(tri.n2, n2);
+    ASSERT_EQ(tri.n3, n3);
+}
+
+TEST(SmoothTriangleTest, An_intersection_with_a_smooth_triangle_stores_u_v)
+{
+    Ray r = Ray(Point(-0.2, 0.3, -2), Vector(0, 0, 1));
+
+    Intersect xs = tri.doLocalIntersect(r);
+
+    ASSERT_TRUE(double_equal(xs[0].u, 0.45));
+    ASSERT_TRUE(double_equal(xs[0].v, 0.25));
+}
+
+TEST(SmoothTriangleTest, A_smooth_triangle_uses_u_v_to_interpolate_the_normal)
+{
+    Intersection i = Intersection(1, &tri, 0.45, 0.25);
+
+    Tuple n = tri.doLocalNormalAt(Point(0, 0, 0), &i);
+
+    /* Temporary lower the precision */
+    set_equal_precision(0.00001);
+
+    ASSERT_EQ(n, Vector(-0.5547, 0.83205, 0));
+
+    set_equal_precision(FLT_EPSILON);
+}
+
+TEST(SmoothTriangleTest, Preparing_a_normal_on_a_smooth_triangle)
+{
+    Intersection i = Intersection(1, &tri, 0.45, 0.25);
+
+    Tuple n = tri.normalAt(Point(0, 0, 0), &i);
+
+    /* Temporary lower the precision */
+    set_equal_precision(0.00001);
+
+    ASSERT_EQ(n, Vector(-0.5547, 0.83205, 0));
+
+    set_equal_precision(FLT_EPSILON);
+}