Metallic material

rtiww/CMakeLists.txt

@@ -6,6 +6,7 @@ set(CMAKE_CXX_STANDARD 17)
 add_executable(rtiww src/main.cpp
   src/vec3.h src/ray.h
   src/color.h
+  src/material.h
   src/hittable.h src/hittable_list.h
   src/sphere.h
   src/camera.h

rtiww/src/color.h

@@ -52,4 +52,20 @@ private:
     }
 };
 
+void write_color(std::ostream &out, color pixel_color,
+                 int samples_per_pixel) {
+    auto r = pixel_color.x();
+    auto g = pixel_color.y();
+    auto b = pixel_color.z();
+
+    auto scale = 1.0 / samples_per_pixel;
+    r = sqrt(scale * r);
+    g = sqrt(scale * g);
+    b = sqrt(scale * b);
+
+    out << static_cast<int>(255.999 * clamp(r, 0.0, 0.999)) << ' '
+        << static_cast<int>(255.999 * clamp(g, 0.0, 0.999)) << ' '
+        << static_cast<int>(255.999 * clamp(b, 0.0, 0.999)) << '\n';
+}
+
 #endif // RTIWW_COLOR_H

rtiww/src/hittable.h

@@ -2,18 +2,23 @@
 #define HITTABLE_H_
 
 #include "ray.h"
+#include "rtweekend.h"
 #include "vec3.h"
+#include <memory>
+
+class material;
 
 struct hit_record {
   point3 p;
   vec3 normal;
+  std::shared_ptr<material> mat_ptr;
   double t;
   bool front_face;
 
-    inline void set_face_normal(const ray& r, const vec3& outward_normal) {
-        front_face = dot(r.direction(), outward_normal) < 0;
-        normal = front_face ? outward_normal: -outward_normal;
-    }
+  inline void set_face_normal(const ray &r, const vec3 &outward_normal) {
+    front_face = dot(r.direction(), outward_normal) < 0;
+    normal = front_face ? outward_normal : -outward_normal;
+  }
 };
 
 class hittable {

rtiww/src/main.cpp

@@ -4,66 +4,79 @@
 
 #include "color.h"
 #include "hittable_list.h"
+#include "material.h"
 #include "sphere.h"
 #include "vec3.h"
 
 #include <iostream>
+#include <memory>
 
 color ray_color(const ray &r, const hittable &world, int depth) {
-  hit_record rec;
-  if (depth <= 0)
-    return color(0, 0, 0);
+    hit_record rec;
 
-  if (world.hit(r, 0.001, infinity, rec)) {
-    point3 target = rec.p + random_in_hemisphere(rec.normal);
-    return 0.5 * ray_color(ray(rec.p, target - rec.p), world, depth - 1);
-  }
+    // If we've exceeded the ray bounce limit, no more light is gathered.
+    if (depth <= 0)
+        return color(0,0,0);
 
-  vec3 unit_direction = unit_vector(r.direction());
-  auto t = 0.5 * (unit_direction.y() + 1.0);
-  return (1.0 - t) * color(1.0, 1.0, 1.0) + t * color(0.5, 0.7, 1.0);
+    if (world.hit(r, 0.000001, infinity, rec)) {
+        ray scattered;
+        color attenuation;
+        if (rec.mat_ptr->scatter(r, rec, attenuation, scattered))
+            return attenuation * ray_color(scattered, world, depth-1);
+        return color(0,0,0);
+    }
+
+    vec3 unit_direction = unit_vector(r.direction());
+    auto t = 0.5*(unit_direction.y() + 1.0);
+    return (1.0-t)*color(1.0, 1.0, 1.0) + t*color(0.5, 0.7, 1.0);
 }
 
 int main() {
 
-  // Image
-  const auto aspect_ratio = 16.0 / 9.0;
-  const int image_width = 400;
-  const int image_height = static_cast<int>(image_width / aspect_ratio);
-  const int samples_per_pixel = 100;
-  const int max_depth = 50;
+    // Image
 
-  // World
-  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));
+    const auto aspect_ratio = 16.0 / 9.0;
+    const int image_width = 400;
+    const int image_height = static_cast<int>(image_width / aspect_ratio);
+    const int samples_per_pixel = 100;
+    const int max_depth = 50;
 
-  // Camera
-  camera cam;
+    // World
 
-  // Render
-  std::cout << "P3\n" << image_width << ' ' << image_height << "\n255\n";
+    hittable_list world;
 
-  picture p;
+    auto material_ground = make_shared<lambertian>(color(0.8, 0.8, 0.0));
+    auto material_center = make_shared<metal>(color(0.7, 0.3, 0.3));
+    auto material_left   = make_shared<metal>(color(0.8, 0.8, 0.8));
+    auto material_right  = make_shared<metal>(color(0.8, 0.6, 0.2));
 
-  for (int j = image_height - 1; j >= 0; --j) {
-    for (int i = 0; i < image_width; ++i) {
-      color pixel_color(0, 0, 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));
 
-      for (int s = 0; s < samples_per_pixel; ++s) {
-        auto u = (i + random_double()) / (image_width - 1);
-        auto v = (j + random_double()) / (image_height - 1);
+    // Camera
 
-        ray r = cam.get_ray(u, v);
-        pixel_color += ray_color(r, world, max_depth);
-      }
+    camera cam;
 
-      p.set_pixel(j, i, pixel_color);
+    // Render
+
+    std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";
+
+    for (int j = image_height-1; j >= 0; --j) {
+        std::cerr << "\rScanlines remaining: " << j << ' ' << std::flush;
+        for (int i = 0; i < image_width; ++i) {
+            color pixel_color(0, 0, 0);
+            for (int s = 0; s < samples_per_pixel; ++s) {
+                auto u = (i + random_double()) / (image_width-1);
+                auto v = (j + random_double()) / (image_height-1);
+                ray r = cam.get_ray(u, v);
+                pixel_color += ray_color(r, world, max_depth);
+            }
+            write_color(std::cout, pixel_color, samples_per_pixel);
+        }
     }
-  }
-
-  p.write(std::cout, image_height, image_width, samples_per_pixel);
-  std::cerr << "\nDone.\n";
 
+    std::cerr << "\nDone.\n";
   return 0;
 }

rtiww/src/material.h

@@ -0,0 +1,57 @@
+#ifndef MATERIAL_H_
+#define MATERIAL_H_
+
+#include "hittable.h"
+#include "rtweekend.h"
+#include "vec3.h"
+
+struct hit_record;
+
+class material {
+public:
+  virtual bool scatter(const ray &r_in, const hit_record &rec,
+                       color &attenuation, ray &scattered) const = 0;
+};
+
+
+
+class lambertian : public material {
+public:
+    lambertian(const color& a) : albedo(a) {}
+
+    virtual bool scatter(
+            const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered
+    ) const override {
+        auto scatter_direction = rec.normal+random_in_unit_sphere();
+
+        // Catch degenerate scatter direction
+        if (scatter_direction.near_zero())
+            scatter_direction = rec.normal;
+
+        scattered = ray(rec.p, scatter_direction);
+        attenuation = albedo;
+        return true;
+    }
+
+public:
+    color albedo;
+};
+
+class metal : public material {
+public:
+    metal(const color& a) : albedo(a) {}
+
+    virtual bool scatter(
+            const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered
+    ) const override {
+        vec3 reflected = reflect(unit_vector(r_in.direction()), rec.normal);
+        scattered = ray(rec.p, reflected);
+        attenuation = albedo;
+        return true;
+    }
+
+public:
+    color albedo;
+};
+
+#endif // MATERIAL_H_

rtiww/src/sphere.h

@@ -2,41 +2,50 @@
 #define SPHERE_H_
 
 #include "hittable.h"
+#include "material.h"
 
-class sphere: public hittable {
+class sphere : public hittable {
 public:
     sphere() {}
-    sphere(point3 cen, double r): center(cen), radius(r) {};
-    virtual bool hit(const ray& r, double t_min, double t_max, hit_record& rec) const override;
+    sphere(point3 cen, double r, shared_ptr<material> m)
+            : center(cen), radius(r), mat_ptr(m) {};
+
+    virtual bool hit(
+            const ray& r, double t_min, double t_max, hit_record& rec) const override;
 
 public:
     point3 center;
     double radius;
+    shared_ptr<material> mat_ptr;
 };
 
-bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const {
-    vec3 oc = r.origin() - center;
-    auto a = r.direction().length_squared();
-    auto half_b = dot(oc, r.direction());
-    auto c = oc.length_squared() - radius*radius;
+bool sphere::hit(const ray &r, double t_min, double t_max,
+                 hit_record &rec) const {
+  vec3 oc = r.origin() - center;
+  auto a = r.direction().length_squared();
+  auto half_b = dot(oc, r.direction());
+  auto c = oc.length_squared() - radius * radius;
 
-    auto discriminant = half_b*half_b - a*c;
-    if(discriminant < 0) return false;
-    auto sqrtd = sqrt(discriminant);
+  auto discriminant = half_b * half_b - a * c;
+  if (discriminant < 0)
+    return false;
+  auto sqrtd = sqrt(discriminant);
 
-    // Find the nearest root that lies in the acceptable range
-    auto root = (-half_b - sqrtd) / a;
-    if(root < t_min || t_max<root) {
-        root = (-half_b + sqrtd) / a;
-        if (root < t_min || t_max < root) return false;
-    }
+  // Find the nearest root that lies in the acceptable range
+  auto root = (-half_b - sqrtd) / a;
+  if (root < t_min || t_max < root) {
+    root = (-half_b + sqrtd) / a;
+    if (root < t_min || t_max < root)
+      return false;
+  }
 
-    rec.t = root;
-    rec.p = r.at(rec.t);
-    vec3 outward_normal = (rec.p - center) / radius;
-    rec.set_face_normal(r, outward_normal);
+  rec.t = root;
+  rec.p = r.at(rec.t);
+  vec3 outward_normal = (rec.p - center) / radius;
+  rec.set_face_normal(r, outward_normal);
+  rec.mat_ptr = mat_ptr;
 
-    return true;
+  return true;
 }
 
 #endif // SPHERE_H_

rtiww/src/vec3.h

@@ -52,6 +52,13 @@ public:
                 random_double(min, max));
   }
 
+  bool near_zero() const {
+    using std::fabs;
+    // Return true if the vector is close to zero in all dimensions.
+    const auto s = 1e-8;
+    return (fabs(e[0]) < s) && (fabs(e[1]) < s) && (fabs(e[2]) < s);
+  }
+
 public:
   double e[3];
 };
@@ -115,4 +122,6 @@ 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; }
+
 #endif // RTIWW_VEC3_H