Lambertian Reflection

.gitignore

@@ -1,4 +1,5 @@
 image.ppm
+debug/
 
 # Created by https://www.toptal.com/developers/gitignore/api/intellij+all,vim,emacs,linux,clion+all
 # Edit at https://www.toptal.com/developers/gitignore?templates=intellij+all,vim,emacs,linux,clion+all

rtiww/src/color.h

@@ -12,9 +12,9 @@ void write_color(std::ostream &out, color pixel_color, int samples_per_pixel) {
   auto b = pixel_color.z();
 
   auto scale = 1.0 / samples_per_pixel;
-  r *= scale;
-  g *= scale;
-  b *= scale;
+  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)) << ' '

rtiww/src/main.cpp

@@ -5,14 +5,20 @@
 #include "color.h"
 #include "hittable_list.h"
 #include "sphere.h"
+#include "vec3.h"
 
 #include <iostream>
 
-color ray_color(const ray &r, const hittable &world) {
+color ray_color(const ray &r, const hittable &world, int depth) {
   hit_record rec;
-  if (world.hit(r, 0, infinity, rec)) {
-    return 0.5 * (rec.normal + color(1, 1, 1));
+  if (depth <= 0)
+    return color(0, 0, 0);
+
+  if (world.hit(r, 0.001, infinity, rec)) {
+    point3 target = rec.p + rec.normal + random_in_unit_sphere();
+    return 0.5 * ray_color(ray(rec.p, target - rec.p), world, depth - 1);
   }
+
   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);
@@ -25,6 +31,7 @@ int main() {
   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;
 
   // World
   hittable_list world;
@@ -46,7 +53,7 @@ int main() {
         auto v = (j + random_double()) / (image_height - 1);
 
         ray r = cam.get_ray(u, v);
-        pixel_color += ray_color(r, world);
+        pixel_color += ray_color(r, world, max_depth);
       }
       write_color(std::cout, pixel_color, samples_per_pixel);
     }

rtiww/src/vec3.h

@@ -1,6 +1,7 @@
 #ifndef RTIWW_VEC3_H
 #define RTIWW_VEC3_H
 
+#include "rtweekend.h"
 #include <cmath>
 #include <ostream>
 
@@ -34,18 +35,22 @@ public:
     return *this;
   }
 
-    vec3& operator/=(const double t) {
-        return *this *= 1/t;
-    }
+  vec3 &operator/=(const double t) { return *this *= 1 / t; }
 
-    double length() const {
-        return sqrt(length_squared());
-    }
+  double length() const { return sqrt(length_squared()); }
 
   double length_squared() const {
     return e[0] * e[0] + e[1] * e[1] + e[2] * e[2];
   }
 
+  inline static vec3 random() {
+    return vec3(random_double(), random_double(), random_double());
+  }
+
+  inline static vec3 random(double min, double max) {
+    return vec3(random_double(min, max), random_double(min, max),
+                random_double(min, max));
+  }
 
 public:
   double e[3];
@@ -74,18 +79,12 @@ inline vec3 operator*(double t, const vec3 &v) {
   return vec3(t * v.e[0], t * v.e[1], t * v.e[2]);
 }
 
-inline vec3 operator*(const vec3 &v, double t) {
-    return t*v;
-}
+inline vec3 operator*(const vec3 &v, double t) { return t * v; }
 
-inline vec3 operator/(vec3 v, double t) {
-    return (1/t) * v;
-}
+inline vec3 operator/(vec3 v, double t) { return (1 / t) * v; }
 
 inline double dot(const vec3 &u, const vec3 &v) {
-    return u.e[0] * v.e[0]
-    + u.e[1] * v.e[1]
-    + u.e[2] * v.e[2];
+  return u.e[0] * v.e[0] + u.e[1] * v.e[1] + u.e[2] * v.e[2];
 }
 
 inline vec3 cross(const vec3 &u, const vec3 &v) {
@@ -94,8 +93,15 @@ inline vec3 cross(const vec3 &u, const vec3 &v) {
               u.e[0] * v.e[1] - u.e[1] * v.e[0]);
 }
 
-inline vec3 unit_vector(vec3 v) {
-    return v / v.length();
+inline vec3 unit_vector(vec3 v) { return v / v.length(); }
+
+vec3 random_in_unit_sphere() {
+  while (true) {
+    auto p = vec3::random(-1, 1);
+    if (p.length_squared() >= 1)
+      continue;
+    return p;
+  }
 }
 
 #endif // RTIWW_VEC3_H