ring.png

README.md

@@ -3,3 +3,9 @@
 Ray tracing rendering experiments
 
 https://raytracing.github.io/
+
+Produced PPM images can be converted to PNG with `imagemagick`:
+
+```
+convert image.ppm image.png
+```

src/camera.h

@@ -5,22 +5,40 @@
 class camera
 {
     public:
-        const double ASPECT_RATIO = 16.0 / 9.0;
-        const double VIEWPORT_HEIGHT = 2.0;
-        const double VIEWPORT_WIDTH = ASPECT_RATIO * VIEWPORT_HEIGHT;
-        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))
+        camera(
+            point3  lookfrom,
+            point3  lookat,
+            vec3    vup,
+            double  vfov,   // vertical field of view in degrees
+            double  aspect_ratio,
+            double  aperture,
+            double  focus_dist)
         {
-            lower_left_corner_ = origin_ - horizontal_/2 - vertical_/2 - vec3(0,0,FOCAL_LENGTH);
+            auto theta = degrees_to_radians(vfov);
+            auto h = tan(theta/2);
+            auto viewport_height = 2.0 * h;
+            auto viewport_width = aspect_ratio * viewport_height;
+
+            w_ = unit_vector(lookfrom - lookat);
+            u_ = unit_vector(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;
         }
 
-        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);
         }
 
     private:
@@ -28,4 +46,6 @@ class camera
         point3  lower_left_corner_;
         vec3    horizontal_;
         vec3    vertical_;
+        vec3    u_, v_, w_;
+        double  lens_radius_;
 };

src/main.cpp

@@ -9,17 +9,22 @@
 #include <iostream>
 
 const double ASPECT_RATIO = 16.0 / 9.0;
-const int WIDTH = 384;
+const int WIDTH = 1920;
 const int HEIGHT = static_cast<int>(WIDTH / ASPECT_RATIO);
-const int SAMPLES_PER_PIXEL = 100;
-const int MAX_DEPTH = 50;
+const int SAMPLES_PER_PIXEL = 8;
+const int MAX_DEPTH = 5;
+
+// fee2aa
+// 
+const colour pink(254.0/255.0, 226.0/255.0, 170.0/255.0);
+const colour grey(0.133, 0.133, 0.133);
 
 colour ray_colour(const ray& r, const hittable& world, int depth)
 {
     hit_record rec;
     if (depth <= 0)
     {
-        return colour(0,0,0);
+        return grey;
     }
 
     if (world.hit(r, 0.001, infinity, rec))
@@ -32,43 +37,96 @@ colour ray_colour(const ray& r, const hittable& world, int depth)
             return attenuation * ray_colour(scattered, world, depth-1);
         }
 
-        return colour(0,0,0);
+        return grey;
     }
 
     vec3 unit_direction = unit_vector(r.direction());
-    auto t = 0.5 * (unit_direction.y() + 1.0);
+    auto t = 0.5 * (unit_direction.y() + 1.0) + 0.5;
 
-    auto a = colour(0.5, 0.6, 0.7);
-    auto b = colour(1.0, 1.0, 1.0);
+    return lerp(grey, pink, t);
+}
 
-    return lerp(a, b, t);
+hittable_list random_scene()
+{
+    hittable_list world;
+
+
+    //auto ground_material = make_shared<lambertian>(pink);
+    //world.add(make_shared<sphere>(point3(0,-1000,0), 1000, ground_material));
+
+    //for (int a = -11; a < 11; a++)
+    //{
+    //    for (int b = -11; b < 11; b++)
+    //    {
+    //        auto choose_mat = random_double();
+    //        point3 centre(a + 0.9*random_double(), 0.2, b + 0.9*random_double());
+
+    //        if ((centre - point3(4, 0.2, 0)).length() > 0.9)
+    //        {
+    //            shared_ptr<material> sphere_material;
+
+    //            if (choose_mat < 0.8)
+    //            {
+    //                // diffuse
+    //                //auto albedo = colour::random() * colour::random();
+    //                sphere_material = make_shared<lambertian>(pink);
+    //                world.add(make_shared<sphere>(centre, 0.2, sphere_material));
+    //            }
+    //            else if (choose_mat < 0.95)
+    //            {
+    //                // metal
+    //                auto fuzz = random_double(0, 0.5);
+    //                sphere_material = make_shared<metal>(pink, fuzz);
+    //                world.add(make_shared<sphere>(centre, 0.2, sphere_material));
+    //            }
+    //            else
+    //            {
+    //                // glass
+    //                sphere_material = make_shared<dielectric>(1.5);
+    //                world.add(make_shared<sphere>(centre,0.2, sphere_material));
+    //            }
+    //        }
+    //    }
+    //}
+
+    auto material1 = make_shared<dielectric>(1.5);
+    world.add(make_shared<sphere>(point3(0, 0, 0), 3.0, material1));
+
+    //auto material2 = make_shared<lambertian>(pink);
+    //world.add(make_shared<sphere>(point3(-4, 1, 0), 1.0, material2));
+    
+    auto material3 = make_shared<metal>(pink, 0.5);
+    int sphere_count = 10;
+    for (int i = 0; i < sphere_count; i++)
+    {
+        float a = 6.28 * (float)i/sphere_count - 100.0;
+        float r = 8.0;
+        float x = r*sin(a);
+        float y = 2.0*cos(a);
+        float z = r*cos(a);
+        point3 pos(x,y,z);
+        world.add(make_shared<sphere>(pos, 2.0, material3));
+    }
+
+
+    return world;
 }
 
 int main()
 {
     std::cout << "P3\n" << WIDTH << ' ' << HEIGHT << "\n255\n";
 
-    hittable_list world;
+    hittable_list world = random_scene();
 
-    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))));
+    auto dist_to_target = 10.0;
+    auto dist_to_focus = dist_to_target + 1.0;
+    auto cam_y = 1.0;
+    point3 lookfrom(0,cam_y,-dist_to_target);
+    point3 lookat(0,0,0);
+    vec3 vup(0,1,0);
+    auto aperture = 0.5;
 
-    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;
+    camera cam(lookfrom, lookat, vup, 47, ASPECT_RATIO, aperture, dist_to_focus);
 
     for (int j = HEIGHT - 1; j >= 0; --j)
     {

src/material.h

@@ -13,6 +13,13 @@ class material
             ray& scattered) const = 0;
 };
 
+double schlick(double cosine, double refraction_index)
+{
+    auto r0 = (1-refraction_index) / (1+refraction_index);
+    r0 = r0*r0;
+    return r0 + (1-r0)*pow(1-cosine, 5);
+}
+
 class lambertian : public material
 {
     public:
@@ -37,7 +44,9 @@ class lambertian : public material
 class metal : public material
 {
     public:
-        metal(const colour& a) : albedo_(a) {}
+        metal(const colour& a, double f) : 
+            albedo_(a),
+            fuzz_(f < 1 ? f : 1) {}
 
     virtual bool scatter(
         const ray& r_in, 
@@ -46,11 +55,55 @@ class metal : public material
         ray& scattered) const 
     {
         vec3 reflected = reflect(unit_vector(r_in.direction()), rec.normal);
-        scattered = ray(rec.p, reflected);
+        scattered = ray(rec.p, reflected + fuzz_*random_in_unit_sphere());
         attenuation = albedo_;
         return dot(scattered.direction(), rec.normal) > 0;
     }
 
     private:
         colour albedo_;
+        double fuzz_;
+};
+
+class dielectric : public material
+{
+    public:
+        dielectric(double ri) : refraction_index_(ri) {}
+
+    virtual bool scatter(
+        const ray& r_in, 
+        const hit_record& rec, 
+        colour& attenuation, 
+        ray& scattered) const 
+    {
+        attenuation = colour(1.0,1.0,1.0);
+        double etai_over_etat = rec.front_face ? (1.0 / refraction_index_) : refraction_index_;
+
+        vec3 unit_direction = unit_vector(r_in.direction());
+
+        double cos_theta = fmin(dot(-unit_direction, rec.normal), 1.0);
+        double sin_theta = sqrt(1.0 - cos_theta*cos_theta);
+        if (etai_over_etat * sin_theta > 1.0)
+        {
+            vec3 reflected = reflect(unit_direction, rec.normal);
+            scattered = ray(rec.p, reflected);
+            return true;
+        }
+
+        double reflect_prob = schlick(cos_theta, etai_over_etat);
+        if (random_double() < reflect_prob)
+        {
+            vec3 reflected = reflect(unit_direction, rec.normal);
+            scattered = ray(rec.p, reflected);
+            return true;
+        }
+
+        vec3 refracted = refract(unit_direction, rec.normal, etai_over_etat);
+        scattered = ray(rec.p, refracted);
+
+        return true;
+    }
+
+    private:
+        double refraction_index_;
 };

src/vec3.h

@@ -160,7 +160,26 @@ vec3 random_in_hemisphere(const vec3& normal)
     }
 }
 
+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;
+    }
+}
+
 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)
+{
+    auto cos_theta = dot(-uv, n);
+    vec3 r_out_parallel = etai_over_etat * (uv + cos_theta*n);
+    vec3 r_out_perp = -sqrt(1.0 - r_out_parallel.length_squared()) * n;
+
+    return r_out_parallel + r_out_perp;
+}