Added Cornell Box example

README.md

@@ -10,6 +10,8 @@ A simple C++ Raytracer based on "Ray Tracing in One Weekend" book.
 
 ![render image with diffuse light](docs/render-light.png)
 
+![render cornell box image](docs/render-cornell-box.png)
+
 ## Features
 
 * Raytracing sphere geometries with front face detection.

src/main.cpp

@@ -148,6 +148,9 @@ void cornell_box() {
     scene->add(make_shared<Quad>(Point(0,0,0), Vector(555,0,0), Vector(0,0,555), white));
     scene->add(make_shared<Quad>(Point(555,555,555), Vector(-555,0,0), Vector(0,0,-555), white));
     scene->add(make_shared<Quad>(Point(0,0,555), Vector(555,0,0), Vector(0,555,0), white));
+
+    scene->add(createBox(Point(130, 0, 65), Point(295, 165, 230), white));
+    scene->add(createBox(Point(265, 0, 295), Point(430, 330, 460), white));
 
     Camera camera(1.0, 500, 50, 1920, 40.0, Vector(278, 278, -800), Vector(278, 278, 0), Vector(0.0, 1.0, 0.0), Color(0.0, 0.0, 0.0), 0.0);
 

src/quad.h

@@ -3,6 +3,7 @@
 #include "intersectable.h"
 #include "material.h"
 #include "aabb.h"
+#include "scene.h"
 
 #include <cmath>
 
@@ -64,3 +65,24 @@ class Quad : public Intersectable {
     }
 
 };
+
+inline std::shared_ptr<Intersectable> createBox(const Point& a, const Point& b, std::shared_ptr<Material> mat)
+{
+    auto sides = std::make_shared<Scene>();
+
+    auto min = Point(std::fmin(a.x(), b.x()), fmin(a.y(), b.y()), fmin(a.z(), b.z()));
+    auto max = Point(std::fmax(a.x(), b.x()), fmax(a.y(), b.y()), fmax(a.z(), b.z()));
+
+    auto dx = Vector(max.x() - min.x(), 0, 0);
+    auto dy = Vector(0, max.y() - min.y(), 0);
+    auto dz = Vector(0, 0, max.z() - min.z());
+
+    sides->add(std::make_shared<Quad>(Point(min.x(), min.y(), max.z()),  dx,  dy, mat)); // front
+    sides->add(std::make_shared<Quad>(Point(max.x(), min.y(), max.z()), -dz,  dy, mat)); // right
+    sides->add(std::make_shared<Quad>(Point(max.x(), min.y(), min.z()), -dx,  dy, mat)); // back
+    sides->add(std::make_shared<Quad>(Point(min.x(), min.y(), min.z()),  dz,  dy, mat)); // left
+    sides->add(std::make_shared<Quad>(Point(min.x(), max.y(), max.z()),  dx, -dz, mat)); // top
+    sides->add(std::make_shared<Quad>(Point(min.x(), min.y(), min.z()),  dx,  dz, mat)); // bottom
+
+    return sides;
+}