add metal material

src/camera.h

@@ -11,9 +11,9 @@ class camera
         const double FOCAL_LENGTH = 1.0;
 
         camera() : 
-            origin_(point3(0,0,0)),
-            horizontal_(vec3(VIEWPORT_WIDTH,0.0,0.0)),
-            vertical_(vec3(0.0, VIEWPORT_HEIGHT, 0.0))
+            origin_     (point3(0,0,0)),
+            horizontal_ (vec3(VIEWPORT_WIDTH,0.0,0.0)),
+            vertical_   (vec3(0.0, VIEWPORT_HEIGHT, 0.0))
         {
             lower_left_corner_ = origin_ - horizontal_/2 - vertical_/2 - vec3(0,0,FOCAL_LENGTH);
         }

src/hittable.h

@@ -1,11 +1,15 @@
 #pragma once
 
+#include "rtweekend.h"
 #include "ray.h"
 
+class material;
+
 struct hit_record
 {
     point3                  p;
     vec3                    normal;
+    shared_ptr<material>    mat_ptr;
     double                  t;
     bool                    front_face;
 

src/main.cpp

@@ -4,6 +4,7 @@
 #include "sphere.h"
 #include "colour.h"
 #include "camera.h"
+#include "material.h"
 
 #include <iostream>
 
@@ -23,8 +24,15 @@ colour ray_colour(const ray& r, const hittable& world, int depth)
 
     if (world.hit(r, 0.001, infinity, rec))
     {
-        point3 target = rec.p + rec.normal + random_in_hemisphere(rec.normal);
-        return 0.5 * ray_colour(ray(rec.p, target - rec.p), world, depth-1);
+        ray     scattered;
+        colour  attenuation;
+
+        if (rec.mat_ptr->scatter(r, rec, attenuation, scattered))
+        {
+            return attenuation * ray_colour(scattered, world, depth-1);
+        }
+
+        return colour(0,0,0);
     }
 
     vec3 unit_direction = unit_vector(r.direction());
@@ -40,18 +48,25 @@ int main()
 {
     std::cout << "P3\n" << WIDTH << ' ' << HEIGHT << "\n255\n";
 
-    auto viewport_height = 2.0;
-    auto viewport_width = ASPECT_RATIO * viewport_height;
-    auto focal_length = 1.0;
-
-    auto origin = point3(0, 0, 0);
-    auto horizontal = vec3(viewport_width, 0, 0);
-    auto vertical = vec3(0, viewport_height, 0);
-    auto lower_left_corner = origin - horizontal/2 - vertical/2 - vec3(0,0,focal_length);
-
     hittable_list world;
-    world.add(make_shared<sphere>(point3(0,0,-1), 0.5));
-    world.add(make_shared<sphere>(point3(0,-100.5,-1), 100));
+    
+    world.add(make_shared<sphere>(
+        point3(0,0,-1),
+        0.5,
+        make_shared<lambertian>(colour(0.7,0.3,0.3))));
+    world.add(make_shared<sphere>(
+        point3(0,-100.5,-1),
+        100,
+        make_shared<lambertian>(colour(0.8,0.8,0.0))));
+
+    world.add(make_shared<sphere>(
+        point3(1,0,-1),
+        0.5,
+        make_shared<metal>(colour(0.8,0.6,0.2))));
+    world.add(make_shared<sphere>(
+        point3(-1,0,-1),
+        0.5,
+        make_shared<metal>(colour(0.8,0.8,0.8))));
 
     camera cam;
 

src/material.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include "rtweekend.h"
+#include "hittable.h"
+
+class material
+{
+    public:
+        virtual bool scatter(
+            const ray& r_in,
+            const hit_record& rec,
+            colour& attenuation,
+            ray& scattered) const = 0;
+};
+
+class lambertian : public material
+{
+    public:
+        lambertian(const colour& a) : albedo_(a) {}
+
+        virtual bool scatter(
+            const ray& r_in, 
+            const hit_record& rec, 
+            colour& attenuation, 
+            ray& scattered) const 
+        {
+            vec3 scatter_direction = rec.normal + random_unit_vector();
+            scattered = ray(rec.p, scatter_direction);
+            attenuation = albedo_;
+            return true;
+        }
+
+    private:
+        colour albedo_;
+};
+
+class metal : public material
+{
+    public:
+        metal(const colour& a) : albedo_(a) {}
+
+    virtual bool scatter(
+        const ray& r_in, 
+        const hit_record& rec, 
+        colour& attenuation, 
+        ray& scattered) const 
+    {
+        vec3 reflected = reflect(unit_vector(r_in.direction()), rec.normal);
+        scattered = ray(rec.p, reflected);
+        attenuation = albedo_;
+        return dot(scattered.direction(), rec.normal) > 0;
+    }
+
+    private:
+        colour albedo_;
+};

src/sphere.h

@@ -7,15 +7,18 @@ class sphere : public hittable
 {
     public:
         sphere() {}
-        sphere(point3 centre, double r) : 
+        sphere(point3 centre, double r, shared_ptr<material> m) : 
             centre_(centre), 
-            radius_(r) {};
+            radius_(r),
+            mat_ptr_(m)
+    {};
 
         virtual bool hit(const ray& r, double t_min, double t_max, hit_record& rec) const;
 
     private:
         point3                  centre_;
         double                  radius_;
+        shared_ptr<material>    mat_ptr_;
 };
 
 bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const 
@@ -38,6 +41,7 @@ bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) cons
 
             vec3 outward_normal = (rec.p - centre_) / radius_;
             rec.set_face_normal(r, outward_normal);
+            rec.mat_ptr = mat_ptr_;
 
             return true;
         }
@@ -50,6 +54,7 @@ bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) cons
             
             vec3 outward_normal = (rec.p - centre_) / radius_;
             rec.set_face_normal(r, outward_normal);
+            rec.mat_ptr = mat_ptr_;
             
             return true;
         }

src/vec3.h

@@ -159,3 +159,8 @@ vec3 random_in_hemisphere(const vec3& normal)
         return -in_unit_sphere;
     }
 }
+
+vec3 reflect(const vec3& v, const vec3& n)
+{
+    return v - 2*dot(v,n)*n;
+}