diff --git a/Makefile b/Makefile
index b5e5e50..2a8eb74 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-raytracer: camera.hpp color.hpp hittable.hpp hittable_list.hpp material.hpp ray.hpp rtweekend.hpp sphere.hpp vec3.hpp
+raytracer: camera.hpp color.hpp hittable.hpp hittable_list.hpp main.cpp material.hpp ray.hpp rtweekend.hpp sphere.hpp vec3.hpp
 	@g++ -g -O2 -Wall -Wextra -Wpedantic main.cpp -o raytracer
 
 image: raytracer
diff --git a/camera.hpp b/camera.hpp
index 3a2f1a8..38e7ceb 100644
--- a/camera.hpp
+++ b/camera.hpp
@@ -8,29 +8,45 @@ struct camera {
     point3 origin;
     point3 lower_left_corner;
     vec3 horizontal;
-    vec3 vertical;    
+    vec3 vertical;
+    vec3 u,v,w;
+    double lens_radius;
     
     /* Constructors */
-    camera()
+    camera(point3 lookfrom,
+           point3 lookat,
+           vec3 vup,
+           double vfov,
+           double aspect_ratio,
+           double aperture,
+           double focus_dist)
     {
-        double aspect_ratio = 16.0 / 9;
-        double viewport_height = 2.0;
+        double theta = degrees_to_radians(vfov);
+        double h = tan(theta/2);
+        double viewport_height = 2.0 * h;
         double viewport_width = aspect_ratio * viewport_height;
-        double focal_length = 1.0;
 
-        origin = vec3(0,0,0);
-        horizontal = vec3(viewport_width, 0, 0);
-        vertical = vec3(0, viewport_height, 0);
-        lower_left_corner = origin - horizontal/2 - vertical/2 - vec3(0, 0, focal_length);        
+        w = normalize(lookfrom - lookat);
+        u = normalize(cross(vup,w));
+        v = cross(w, u);
+
+        origin = lookfrom;
+        horizontal = focus_dist * viewport_width * u;
+        vertical = focus_dist * viewport_height * v;
+        lower_left_corner = origin - horizontal/2 - vertical/2 - focus_dist*w;
+
+        lens_radius = aperture/2;
     }
 
     /* Methods */    
 
-    ray get_ray(double u, double v) const
+    ray get_ray(double s, double t) const
     {
-        return ray(origin, lower_left_corner + u*horizontal + v*vertical - origin);
+        vec3 rd = lens_radius * random_in_unit_disk();
+        vec3 offset = u * rd.x + v * rd.y;
+
+        return ray(origin + offset, lower_left_corner + s*horizontal + t*vertical - origin - offset);
     };
-       
 };
 
 #endif
diff --git a/main.cpp b/main.cpp
index c7ca4f0..f6b7e83 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdint.h>
+#include <stdlib.h>
 
 #include "rtweekend.hpp"
 
@@ -8,8 +9,63 @@
 #include "sphere.hpp"
 #include "camera.hpp"
 
+
 color ray_color(const ray& r, const hittable& world, int32_t depth);
 double hit_sphere(const point3& center, double radius, const ray& r);
+hittable_list random_scene();
+
+hittable_list random_scene() {
+    hittable_list world;
+
+    auto ground_material = make_shared<lambertian>(color(0.5, 0.5, 0.5));
+    world.add(make_shared<sphere>(point3(0,-1000,0), 1000, ground_material));
+
+    for (int32_t a = -11; a < 11; a++)
+    {
+        for (int32_t b = -11; b < 11; b++)
+        {
+            double choose_mat = random_double();
+            point3 center(a + 0.9*random_double(), 0.2, b + 0.9*random_double());
+
+            if ((center - point3(4, 0.2, 0)).length() > 0.9)
+            {
+                shared_ptr<material> sphere_material;
+                if (choose_mat < 0.8)
+                {
+                    // diffuse
+                    color albedo = color::random() * color::random();
+                    sphere_material = make_shared<lambertian>(albedo);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                }
+                else if (choose_mat < 0.95)
+                {
+                    // metal
+                    color albedo = color::random(0.5, 1);
+                    double fuzz = random_double(0, 0.5);
+                    sphere_material = make_shared<metal>(albedo, fuzz);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                }
+                else
+                {
+                    // glass
+                    sphere_material = make_shared<dielectric>(1.5);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                }
+            }
+        }
+    }
+
+    auto material1 = make_shared<dielectric>(1.5);
+    world.add(make_shared<sphere>(point3(0, 1, 0), 1.0, material1));
+
+    auto material2 = make_shared<lambertian>(color(0.4, 0.2, 0.1));
+    world.add(make_shared<sphere>(point3(-4, 1, 0), 1.0, material2));
+
+    auto material3 = make_shared<metal>(color(0.7, 0.6, 0.5), 0.0);
+    world.add(make_shared<sphere>(point3(4, 1, 0), 1.0, material3));
+
+    return world;
+}
 
 color ray_color(const ray& r, const hittable& world, int32_t depth)
 {
@@ -50,18 +106,16 @@ double hit_sphere(const point3& center, double radius, const ray& r)
     else
         return (-half_b - sqrt(discriminant)) / a;
 }
-
-int main()
+int32_t main()
 {
 
 
-    
     // Image
-    double aspect_ratio = 16.0 / 9;
-    const int32_t image_width = 400;
+    const double aspect_ratio = 3.0 / 2.0;
+    const int32_t image_width = 1200;
     const int32_t image_height = (int32_t) (image_width / aspect_ratio);
-    int32_t samples_per_pixel = 100;
-    int32_t max_depth = 50;
+    int32_t samples_per_pixel = 500;
+    const int32_t max_depth = 50;
 
     if (getenv("SPP"))
     {        
@@ -71,21 +125,16 @@ int main()
     
 
     // World
-    hittable_list world;
-
-    std::shared_ptr<lambertian> material_ground = make_shared<lambertian>(color(0.8, 0.8, 0.0));
-    std::shared_ptr<lambertian> material_center = make_shared<lambertian>(color(0.7, 0.3, 0.3));
-    std::shared_ptr<metal> material_left   = make_shared<metal>(color(0.8, 0.8, 0.8), 0.3);
-    std::shared_ptr<metal> material_right  = make_shared<metal>(color(0.8, 0.6, 0.2), 1.0);
-
-    world.add(make_shared<sphere>(point3( 0.0, -100.5, -1.0), 100.0, material_ground));
-    world.add(make_shared<sphere>(point3( 0.0,    0.0, -1.0),   0.5, material_center));
-    world.add(make_shared<sphere>(point3(-1.0,    0.0, -1.0),   0.5, material_left));
-    world.add(make_shared<sphere>(point3( 1.0,    0.0, -1.0),   0.5, material_right));
-        
+    hittable_list world = random_scene();        
 
     // Camera
-    camera cam;
+    point3 lookfrom(13,2,3);
+    point3 lookat(0,0,0);
+    vec3 vup(0,1,0);
+    double dist_to_focus = 10.0;
+    double aperture = 0.1;
+
+    camera cam(lookfrom, lookat, vup, 20, aspect_ratio, aperture, dist_to_focus);
 
     // Render
     printf("P3\n%d %d\n255\n", image_width, image_height);
diff --git a/material.hpp b/material.hpp
index b8f93e8..5792e38 100644
--- a/material.hpp
+++ b/material.hpp
@@ -54,4 +54,47 @@ struct metal : material {
     }
 };
 
+struct dielectric : material
+{
+    /* Attributes */
+    double ri; // refraction index
+    
+    // Constructor
+    dielectric(double refraction_index) { ri = refraction_index; }
+
+    /* Methods */
+
+    // Schlick's approximation of reflectance
+    static double reflectance(double cosine, double ref_idx)
+    {
+        double r0 = (1-ref_idx) / (1+ref_idx);
+        r0 = r0*r0;
+        return r0 + (1-r0)*pow((1 - cosine), 5);
+    }
+                            
+
+    /* Virtual methods */
+    virtual bool scatter(const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered) const override
+    {
+        attenuation = color(1,1,1);
+        double refraction_ratio = rec.front_face ? (1.0/ri) : ri;
+
+        vec3 unit_direction = normalize(r_in.direction);
+
+        double cos_theta = fmin(dot(-unit_direction, rec.normal), 1);
+        double sin_theta = sqrt(1.0 - cos_theta*cos_theta);
+
+        bool cannot_refract = refraction_ratio * sin_theta > 1.0;
+        vec3 direction;
+
+        if (cannot_refract || reflectance(cos_theta, refraction_ratio) > random_double())
+            direction = reflect(unit_direction, rec.normal);
+        else
+            direction = refract(unit_direction, rec.normal, refraction_ratio);
+
+        scattered = ray(rec.p, direction);
+        return true;
+    }
+};
+
 #endif
diff --git a/vec3.hpp b/vec3.hpp
index 751257b..8d51c82 100644
--- a/vec3.hpp
+++ b/vec3.hpp
@@ -188,4 +188,22 @@ vec3 reflect(const vec3& v, const vec3 n)
     return v - 2*dot(v,n)*n;
 }
 
+vec3 refract (const vec3& uv, const vec3& n, double etai_over_etat)
+{
+    double cos_theta = fmin(dot(-uv, n), 1.0);
+    vec3 r_out_perp = etai_over_etat * (uv + cos_theta*n);
+    vec3 r_out_parallel = -sqrt(fabs(1.0 - r_out_perp.length_squared())) * n;
+    return r_out_perp + r_out_parallel;
+}
+
+vec3 random_in_unit_disk()
+{
+    while (true)
+    {
+        auto p = vec3(random_double(-1,1), random_double(-1,1), 0);
+        if (p.length_squared() >= 1) continue;
+        return p;
+    }
+}
+
 #endif